vendex and Spinal-Cord-Injuries

The dose de-escalation (DD) effects of testosterone and evoked resistance training (RT) on body composition, cardiometabolic, and neuromuscular variables were investigated. Thirteen men with chronic complete spinal cord injury (SCI) were followed for additional 16 weeks after receiving either testosterone treatment only (TT) or TT+RT. During the 16-week DD period, the TT+RT group underwent a program of once weekly electrical stimulation with gradually decreasing ankle weights and testosterone patches of 2 mg day

Topics: Adult; Basal Metabolism; Blood Glucose; Body Composition; Carbohydrate Metabolism; Humans; Knee; Lipid Metabolism; Male; Middle Aged; Muscle, Skeletal; Resistance Training; Spinal Cord Injuries; Testosterone; Torque

Traumatic spinal cord injury (TSCI) is one of the most devastating injuries that has a physical impact on patients. The CHORDATA® method involves suspension and pendulous exercises and has been clinically used to treat patients with TSCI. Although empirically used to treat neurological patients, there is no scientific evidence of the efficacy of this method.. To evaluate the chronic effects of CHORDATA® method on torque, muscle activation, muscle thickness, and functionality in patients with traumatic spinal cord injury.. Twenty-six male patients with medullar thoracic injury were randomly categorised into two groups: intervention group (n = 14) and control group (n = 12). Rehabilitation program comprised of 16 sessions of body suspension and pendulum exercises (twice/week). The maximal voluntary isometric trunk flexion and extension torques, muscle activation and thickness (external and internal oblique, rectus and transversus abdominis, longissimus, and multifidus muscles), and functionality (adapted reach test) were evaluated before and after of rehabilitation program.. A significant increase was observed in maximal voluntary isometric torque (flexion, 58%; extension, 76%), muscle activation of the rectus abdominis muscle, and muscle thickness of all intervention group muscles, without changes in the control group. Compared to the pre-intervention period, the intervention group also showed improvement in functionality at post-intervention, but no such differences were noted in the control group.. The corporal suspension and pendulum exercises training improved rectus abdominis muscle activation, trunk muscles structure and strength, and reaching capacity in medullar thoracic injury patients.

Topics: Abdominal Muscles; Abdominal Oblique Muscles; Adolescent; Adult; Aged; Electromyography; Exercise Therapy; Humans; Male; Middle Aged; Muscle, Skeletal; Rectus Abdominis; Spinal Cord Injuries; Thoracic Injuries; Torque; Torso; Young Adult

To investigate the effects of antispastic drugs baclofen and tizanidine on reflexes and volitional tasks.. Double-blind, placebo-controlled, crossover, before-after trial, pilot study.. Research laboratory in a rehabilitation hospital.. Men with chronic (>6mo) motor incomplete spinal cord injury (N=10) were recruited for the study.. Tizanidine, baclofen, and placebo were tested in this study. Agents were tested in separate experimental sessions separated by >1 week.. Reflex and strength were measured before and after the administration of a single dose of each intervention agent. Electromyographic and joint torque data were collected during assessments of plantar flexor stretch reflexes, maximum contraction during motor-assisted isokinetic movements, and maximum isometric knee extension and flexion.. Reduced stretch reflex activity was observed after the administration of either tizanidine or baclofen. We observed that tizanidine had a stronger inhibitory effect on knee extensors and plantar flexors whereas baclofen had a stronger inhibitory effect on the knee flexors. The effects of these drugs on strength during isometric and isokinetic tasks varied across participants, without a consistent reduction in torque output despite decreased electromyographic activity.. These results suggest that antispastic drugs are effective in reducing stretch reflexes without substantially reducing volitional torque. Differential effects of tizanidine and baclofen on reflexes of flexors and extensors warrant further investigation into patient-specific management of antispastic drugs.

Topics: Adult; Baclofen; Clonidine; Cross-Over Studies; Double-Blind Method; Electromyography; Humans; Isometric Contraction; Lower Extremity; Male; Middle Aged; Muscle Relaxants, Central; Muscle Strength; Pilot Projects; Reflex, Stretch; Spinal Cord Injuries; Torque

This study investigated whether the relationship between muscle torque and m-waves remained constant after short recovery periods, between repeated intervals of isometric muscle contractions induced by functional electrical stimulation (FES). Eight subjects with spinal cord injury (SCI) were recruited for the study. All subjects had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The evoked-electromyographic (eEMG) signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. All analysed m-wave variables changed progressively throughout the three contractions, even though the same muscle torque was generated. The peak to peak amplitude (PtpA), and the m-wave area (Area) were significantly increased, while the time between the stimulus artefact and the positive peak (PosT) were substantially reduced when the muscles became fatigued. In addition, all m-wave variables recovered faster and to a greater extent than did torque after the recovery intervals. We concluded that rapid recovery intervals between FES-evoked exercise sessions can radically interfere in the use of m-waves as a proxy for torque estimation in individuals with SCI. This needs to be further investigated, in addition to seeking a better understanding of the mechanisms of muscle fatigue and recovery.

Topics: Algorithms; Electric Stimulation Therapy; Electromyography; Humans; Isometric Contraction; Male; Middle Aged; Muscle Fatigue; Muscle Strength; Recovery of Function; Reproducibility of Results; Sensitivity and Specificity; Spinal Cord Injuries; Torque

To investigate the long-term effects of functional electrical stimulation (FES)-evoked cycle training cadence on leg muscle hypertrophy and electrically evoked strength.. Open intervention study.. Laboratory setting.. Untrained individuals with chronic spinal cord injury (N=8).. Six weeks (3d/wk) of training on an isokinetic FES cycle ergometer. For each subject, 1 leg was randomly allocated to cycling at 10 revolutions per minute (rpm) (LOW) for 30min/d, and the other cycling at 50rpm (HIGH) for 30min/d.. Pre- and posttraining measurements of lower limb circumference were performed at the distal and middle position of each thigh. Electrically evoked quadriceps muscle torque during an isometric contraction was also assessed.. Six weeks of FES cycle training significantly increased thigh girth in both LOW and HIGH groups. At midthigh, girth increases induced by LOW (6.6%±1.2%) were significantly greater than those by HIGH (3.6%±0.8%). LOW also produced greater gains in electrically evoked isometric torque than HIGH after training.. These results suggest that lower pedaling cadences evoke greater muscle hypertrophy and electrically stimulated muscle strength compared with higher cadences.

Topics: Adult; Bicycling; Electric Stimulation Therapy; Exercise Therapy; Humans; Middle Aged; Muscle Strength; Organ Size; Pilot Projects; Quadriceps Muscle; Spinal Cord Injuries; Torque

Neural plasticity may contribute to motor recovery following spinal cord injury (SCI). In rat models of SCI with respiratory impairment, acute intermittent hypoxia (AIH) strengthens synaptic inputs to phrenic motor neurons, thereby improving respiratory function by a mechanism known as respiratory long-term facilitation. Similar intermittent hypoxia-induced facilitation may be feasible in somatic motor pathways in humans.. Using a randomized crossover design, the authors tested the hypothesis that AIH increases ankle strength in people with incomplete SCI.. Ankle strength was measured in 13 individuals with chronic, incomplete SCI before and after AIH. Voluntary ankle strength was estimated using changes in maximum isometric ankle plantar flexion torque generation and plantar flexor electromyogram activity following 15 low oxygen exposures (Fio(2) = 0.09, 1-minute intervals). Results were compared with trials where subjects received sham exposure to room air.. AIH increased plantar flexion torque by 82 ± 33% (P < .003) immediately following AIH and was sustained above baseline for more than 90 minutes (P < .007). Increased ankle plantar flexor electromyogram activity (P = .01) correlated with increased torque (r(2) = .5; P < .001). No differences in plantar flexion strength or electromyogram activity were observed in sham experiments.. AIH elicits sustained increases in volitional somatic motor output in persons with chronic SCI. Thus, AIH has promise as a therapeutic tool to induce plasticity and enhance motor function in SCI patients.

Topics: Adult; Analysis of Variance; Ankle; Cross-Over Studies; Electromyography; Female; Humans; Hypoxia; Isometric Contraction; Linear Models; Male; Middle Aged; Muscle Strength Dynamometer; Recovery of Function; Respiration Disorders; Spinal Cord Injuries; Time Factors; Torque

The objectives of this study were to probe the contribution of spinal neuron persistent sodium conductances to reflex hyperexcitability in human chronic spinal cord injury. The intrinsic excitability of spinal neurons provides a novel target for medical intervention. Studies in animal models have shown that persistent inward currents, such as persistent sodium currents, profoundly influence neuronal excitability, and recovery of persistent inward currents in spinal neurons of animals with spinal cord injury routinely coincides with the appearance of spastic reflexes. Pharmacologically, this neuronal excitability can be decreased by agents that reduce persistent inward currents, such as the selective persistent sodium current inhibitor riluzole. We were able to recruit seven subjects with chronic incomplete spinal cord injury who were not concurrently taking antispasticity medications into the study. Reflex responses (flexion withdrawal and H-reflexes) and volitional strength (isometric maximum voluntary contractions) were tested at the ankle before and after placebo-controlled, double-blinded oral administration of riluzole (50 mg). Riluzole significantly decreased the peak ankle dorsiflexion torque component of the flexion withdrawal reflex. Peak maximum voluntary torque in both dorsiflexion and plantarflexion directions was not significantly changed. Average dorsiflexion torque sustained during the 5-s isometric maximum voluntary contraction, however, increased significantly. There was no effect, however, on the monosynaptic plantar and dorsiflexor H-reflex responses. Overall, these results demonstrate a contribution of persistent sodium conductances to polysynaptic reflex excitability in human chronic spinal cord injury without a significant role in maximum strength production. These results suggest that intrinsic spinal cellular excitability could be a target for managing chronic spinal cord injury hyperreflexia impairments without causing a significant loss in volitional strength.

Topics: Adult; Analysis of Variance; Ankle; Double-Blind Method; Electric Stimulation; Electromyography; Female; Humans; Male; Middle Aged; Movement Disorders; Muscle Contraction; Muscle Spasticity; Muscle, Skeletal; Neuroprotective Agents; Reflex; Riluzole; Sensory Thresholds; Spinal Cord Injuries; Torque

A better understanding of autonomic influence on motor reflex pathways in spinal cord injury is important to the clinical management of autonomic dysreflexia and spasticity in spinal cord injured patients. The purpose of this study was to examine the modulation of flexor reflex windup during episodes of induced sympathetic activity in chronic human spinal cord injury (SCI). We simultaneously measured peripheral vascular conductance and the windup of the flexor reflex in response to conditioning stimuli of electrocutaneous stimulation to the opposite leg and bladder percussion. Flexor reflexes were quantified using torque measurements of the response to a noxious electrical stimulus applied to the skin of the medial arch of the foot. Both bladder percussion and skin conditioning stimuli produced a reduction (43-67%) in the ankle and hip flexor torques (p<0.05) of the flexor reflex. This reduction was accompanied by a simultaneous reduction in vascular conductance, measured using venous plethysmography, with a time course that matched the flexor reflex depression. While there was an overall attenuation of the flexor reflex, windup of the flexor reflex to repeated stimuli was maintained during periods of increased sympathetic activity. This paradoxical depression of flexor reflexes and minimal effect on windup is consistent with inhibition of afferent feedback within the superficial dorsal horn. The results of this study bring attention to the possible interaction of motor and sympathetic reflexes in SCI above and below the T5 spinal level, and have implications for clinicians in spasticity management and for researchers investigating motor reflexes post SCI.

Topics: Adult; Biophysics; Chronic Disease; Electric Stimulation; Electromyography; Female; Humans; Male; Middle Aged; Multivariate Analysis; Muscle, Skeletal; Reflex; Skin; Spinal Cord Injuries; Sympathetic Nervous System; Torque; Urinary Bladder; Young Adult

To determine the influence of pedaling cadence on cardiorespiratory responses and muscle oxygenation during functional electric stimulation (FES) leg cycling.. Repeated measures.. Laboratory.. Nine subjects with T4 through T10 spinal cord injury (SCI) (American Spinal Injury Association grade A).. FES cycling was performed at pedaling cadences of 15, 30, and 50 revolutions per minute (rpm).. At each cadence, heart rate, oxygen uptake, and cardiac output were recorded during 35 minutes of cycling. Near infrared spectroscopy was used to quantify quadriceps muscle oxygenation.. All pedaling cadences induced similar elevations in cardiorespiratory metabolism, compared with resting values. Higher average power output was produced at 30rpm (8.2+/-0.7W, P<.05) and 50rpm (7.9+/-0.5W, P<.05) compared with 15rpm (6.3+/-0.6W). Gross mechanical efficiency was significantly higher (P<.05) at 30 and 50rpm than at 15rpm. Quadriceps muscle oxygenation did not differ with pedaling cadences.. Cardiorespiratory responses and muscle metabolism adjustments during FES leg cycling were independent of pedal cadence. FES cycling at a cadence of 50rpm may not confer any advantages over 30 or 15rpm for cardiovascular fitness promotion in persons with SCI.

Topics: Adult; Bicycling; Cardiovascular Physiological Phenomena; Electric Stimulation; Energy Metabolism; Exercise Test; Exercise Tolerance; Female; Follow-Up Studies; Humans; Male; Middle Aged; Muscle Fatigue; Oxygen Consumption; Paraplegia; Physical Exertion; Probability; Reference Values; Respiratory Mechanics; Spectroscopy, Near-Infrared; Spinal Cord Injuries; Stroke Volume; Torque

The aims of this study were to identify the reflex moment induced by flexion withdrawal reflex and to optimize stimulation parameters for restoring swing motion with respect to initial kinematic conditions in human with spinal cord injury.. The influence of hip position and passive movement in the reflex moment were tested in six subjects with chronic spinal cord injury. The two-dimensional dynamic models consisted of thigh, shank and foot segments were developed to compute the swing-phase response and the response surface method was also used to optimize stimulation parameters for restoration of gait by functional electrical stimulation.. At three different hip positions, significant linear relationship was found between the reflex moment and hip angle (P < 0.05) and hip movement also increased the reflex moment compare to isometric conditions. The hip and knee flexion velocities significantly contributed to the hip and knee flexion angle during the swing-phase (P < 0.05) and increase of initial joint velocity resulted in a decrease of the burst frequency and duration time for optimal swing motion in spinal cord injured patients.. From dynamic simulation, we concluded that optimal solutions of pulse amplitude, frequency and duration time of burst for electrical stimulation assisted gait were influenced by initial kinematic conditions at toe-off. The reflex model and the results of this study can be applied to the design and control strategies of neuroprosthetic devices using functional electrical stimulation for spinal cord injured patients.

Topics: Adult; Computer Simulation; Electric Stimulation Therapy; Gait Disorders, Neurologic; Humans; Leg; Male; Models, Biological; Muscle Contraction; Muscle, Skeletal; Reflex; Spinal Cord Injuries; Therapy, Computer-Assisted; Torque; Treatment Outcome

Recent evidence suggests that alterations in ionic conductances in spinal motoneurones, specifically the manifestation of persistent inward currents, may be partly responsible for the appearance of hyperexcitable reflexes following spinal cord injury (SCI). We hypothesized that such alterations would manifest as temporal facilitation of stretch reflexes in human SCI. Controlled, triangular wave, ankle joint rotations applied at variable velocities (30-120 deg s(-1)) and intervals between stretches (0.25-5.0 s) were performed on 14 SCI subjects with velocity-dependent, hyperexcitable plantarflexors. Repeated stretch elicited significant increases in plantarflexion torques and electromyographic (EMG) activity from the soleus (SOL) and medial gastrocnemius (MG). At higher velocities (> or = 90 deg s(-1)), reflex torques declined initially, but subsequently increased to levels exceeding the initial response, while mean EMG responses increased throughout the joint perturbations. At lower velocities (< or = 60 deg s(-1)), both joint torques and EMGs increased gradually. Throughout a range of angular velocities, reflex responses increased significantly only at intervals < or = 1 s between stretches and following at least four rotations. Ramp-and-hold perturbations used to elicit tonic stretch reflexes revealed significantly prolonged EMG responses following one or two triangular stretches, as compared to single ramp-and-hold excursions. Post hoc analyses revealed reduced reflex facilitation in subjects using baclofen to control spastic behaviours. Evidence of stretch reflex facilitation post-SCI may reflect changes in underlying neuronal properties and provide insight into the mechanisms underlying spastic reflexes.

Topics: Adult; Ankle Joint; Baclofen; Electromyography; Female; Humans; Male; Middle Aged; Motor Neurons; Muscle Contraction; Muscle Relaxants, Central; Muscle, Skeletal; Reflex, Abnormal; Reflex, Stretch; Spasm; Spinal Cord Injuries; Time Factors; Torque

Understanding the torque output behavior of paralyzed muscle has important implications for the use of functional neuromuscular electrical stimulation systems. Postfatigue potentiation is an augmentation of peak muscle torque during repetitive activation after a fatigue protocol. The purposes of this study were 1) to quantify postfatigue potentiation in the acutely and chronically paralyzed soleus and 2) to determine the effect of long-term soleus electrical stimulation training on the potentiation characteristics of recently paralyzed soleus muscle. Five subjects with chronic paralysis (>2 yr) demonstrated significant postfatigue potentiation during a repetitive soleus activation protocol that induced low-frequency fatigue. Ten subjects with acute paralysis (<6 mo) demonstrated no torque potentiation in response to repetitive stimulation. Seven of these acute subjects completed 2 yr of home-based isometric soleus electrical stimulation training of one limb (compliance = 83%; 8,300 contractions/wk). With the early implementation of electrically stimulated training, potentiation characteristics of trained soleus muscles were preserved as in the acute postinjury state. In contrast, untrained limbs showed marked postfatigue potentiation at 2 yr after spinal cord injury (SCI). A single acute SCI subject who was followed longitudinally developed potentiation characteristics very similar to the untrained limbs of the training subjects. The results of the present investigation support that postfatigue potentiation is a characteristic of fast-fatigable muscle and can be prevented by timely neuromuscular electrical stimulation training. Potentiation is an important consideration in the design of functional electrical stimulation control systems for people with SCI.

Topics: Adaptation, Physiological; Adult; Biomechanical Phenomena; Electric Stimulation; Electric Stimulation Therapy; Humans; Long-Term Potentiation; Male; Middle Aged; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Spinal Cord Injuries; Torque

Chronically paralyzed muscle requires extensive training before it can deliver a therapeutic dose of repetitive stress to the musculoskeletal system. Neuromuscular electrical stimulation, under feedback control, may subvert the effects of fatigue, yielding more rapid and extensive adaptations to training. The purposes of this investigation were to 1) compare the effectiveness of torque feedback-controlled (FDBCK) electrical stimulation with classic open-loop constant-frequency (CONST) stimulation, and 2) ascertain which of three stimulation strategies best maintains soleus torque during repetitive stimulation. When torque declined by 10%, the FDBCK protocol modulated the base stimulation frequency in three ways: by a fixed increase, by a paired pulse (doublet) at the beginning of the stimulation train, and by a fixed decrease. The stimulation strategy that most effectively restored torque continued for successive contractions. This process repeated each time torque declined by 10%. In fresh muscle, FDBCK stimulation offered minimal advantage in maintaining peak torque or mean torque over CONST stimulation. As long-duration fatigue developed in subsequent bouts, FDBCK stimulation became most effective ( approximately 40% higher final normalized torque than CONST). The high-frequency strategy was selected approximately 90% of the time, supporting that excitation-contraction coupling compromise and not neuromuscular transmission failure contributed to fatigue of paralyzed muscle. Ideal stimulation strategies may vary according to the site of fatigue; this stimulation approach offered the advantage of online modulation of stimulation strategies in response to fatigue conditions. Based on stress-adaptation principles, FDBCK-controlled stimulation may enhance training effects in chronically paralyzed muscle.

Topics: Adaptation, Physiological; Adult; Aged; Electric Stimulation; Electric Stimulation Therapy; Feedback; Humans; Male; Middle Aged; Muscle Fatigue; Muscle, Skeletal; Paraplegia; Spinal Cord Injuries; Torque

To investigate the influence of rhythmic passive movements of the legs on the reduction of spasticity after spinal cord injury (SCI).. Swiss Paraplegic Centre Nottwil, Switzerland.. A total of 10 subjects with motor complete SCI were treated with a cycling device for half an hour. Before and after cycling their spasticity was tested with an isokinetic dynamometer. The subjects were tested one week later by exactly the same procedure with a half an hour break instead of the cycling. Subjects were asked about their spasticity before and after the cycling and break.. There was no significant difference in elicited peak torque either before and after the cycling, or before and after the break (MANOVA, P<0.05). Six out of 10 subjects estimated their spasticity as less after the cycling.. With the isokinetic dynamometer, it was not possible to show an effect of passive cycling on spasticity reduction. However, six out of 10 of the subjects estimated their spasticity to be less after cycling. This positive effect might be attributed to a reduced spasticity in the trunk and/or to the attention the subjects perceived during the intervention.

Topics: Adult; Biomechanical Phenomena; Female; Humans; Knee Joint; Male; Middle Aged; Multivariate Analysis; Muscle Spasticity; Muscle, Skeletal; Physical Therapy Modalities; Reaction Time; Spinal Cord Injuries; Torque; Treatment Outcome

Contracture, or loss of range of motion (ROM) of a joint, is a common clinical problem in individuals with spinal cord injury (SCI). In order to measure the possible contribution of changes in muscle length to the loss of ankle ROM, the active force vs. angle curves for the tibialis anterior (TA) and gastrocnemiussoleus (GS) were measured in 20 participants, 10 with SCI, and 10 gender and age matched, neurologically intact (NI) individuals. Electrical stimuli were applied to the TA and GS motor nerves at incremented angles of the entire ROM of the ankle and the resulting ankle and knee torques were measured using a multi-axis load cell. The muscle forces of the TA and GS were calculated from the torque measurements using estimates of their respective moment arms and the resulting forces were plotted against joint angle. The force-angle relation for the GS at the ankle (GSA) was significantly shifted into plantar flexion in SCI subjects, compared to NI controls (t-test, p<0.001). Similar results were obtained based upon the GS knee (GSK) force-angle measurements (p<0.05). Conversely, no significant shift in the force-angle relation was found for the TA (p=0.138). Differences in the passive ROM were consistent with the force-angle changes. The ROM in the dorsiflexion direction was significantly smaller in SCI subjects compared to NI controls (p<0.05) while the plantar flexion ROM was not significantly different (p=0.114). Based upon these results, we concluded that muscle shortening is an important component of contracture in SCI.

Topics: Adult; Ankle Joint; Cervical Vertebrae; Computer Simulation; Contracture; Electric Stimulation; Female; Humans; Male; Middle Aged; Models, Biological; Muscle Contraction; Muscle, Skeletal; Range of Motion, Articular; Spinal Cord Injuries; Stress, Mechanical; Thoracic Vertebrae; Torque

This study describes the performance of surgically-implanted epimysial stimulating electrodes in the muscles of the lower extremities for use in functional neuromuscular stimulation (FNS) systems for standing after spinal cord injury. A total of 86 epimysial electrodes were implanted in 13 volunteers with low tetraplegia or paraplegia receiving the Case Western Reserve University/Veteran Affairs (CWRU/VA)-implanted standing/transfer neuroprosthesis. The neuroprosthesis consisted of bilateral epimysial electrodes in the knee and hip extensors (vastus lateralis, gluteus maximus, and adductor magnus or semimembranosus) and intramuscular electrodes at the T12/L1 or L1/L2 spinal roots for trunk extension. Recruitment properties, stimulated knee and hip extension moments, standing performance, and mechanical integrity over time were measured for a period up to four years post-implantation. Stimulated thresholds were stable and recruitment was sufficient to generate joint moments adequate for standing, with up to 97% body weight supported by the legs. Four mechanical failures were observed, all in the posterior muscles of the thigh, leaving 95% of all electrodes operational at all followup intervals. Probability of 24-month survival is estimated to be 93% plateauing to a steady state of 90% at four years. These results indicate that epimysial designs are appropriate for long-term clinical use in the large muscles of the lower extremities with implanted motor system neuroprostheses.

Topics: Adult; Electric Stimulation Therapy; Electrodes, Implanted; Equipment Design; Equipment Failure Analysis; Female; Humans; Lower Extremity; Male; Microelectrodes; Middle Aged; Muscle Contraction; Muscle, Skeletal; Paraplegia; Spinal Cord Injuries; Stress, Mechanical; Torque; Treatment Outcome

Neuromuscular electrical stimulation was used to evoke isometric knee extension contractions in seven individuals with spinal cord injury (SCI) and the time for knee extension torque to rise and fall was measured across a range of knee angles. The stimulated muscles took more than twice as long to develop 50% of maximum torque at an angle of 15 degrees, compared to an angle of 90 degrees. This time difference comprised both an increased delay before torque rose above resting levels (31 +/- 3 ms at 90 degrees, 67 +/- 24 ms at 15 degrees), and a prolonged duration over which torque was rising (72 +/- 14 ms at 90 degrees, 140 +/- 62 ms at 15 degrees). There was no change, however, in the time taken for torque to fall after cessation of stimulation at different knee angles (58 +/- 5-ms delay, 60 +/- 11-ms fall time). The difference in torque rise time with joint angle has implications for modeling functional activities that differ greatly in their joint angles. This study provides regression equations whereby activation times for the quadriceps muscles of individuals with SCI can be predicted for specific angles of knee flexion.

Topics: Adult; Electric Stimulation; Electric Stimulation Therapy; Female; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Muscle, Skeletal; Paraparesis; Rotation; Spinal Cord Injuries; Thoracic Vertebrae; Time Factors; Torque

A hybrid functional-electrical stimulation (FES) gait system that incorporates a computer-controlled orthosis system has been developed to address the problems of rapid muscle fatigue and poor movement control that are characteristic of FES-aided gait. The orthosis is a long-leg brace that contains controllable friction brakes at both hip and knee joints. The system achieves desirable limb trajectories by utilizing the stimulated muscles as a source of unregulated power and regulating the power at each joint by computer control of the friction brakes. Muscle fatigue is reduced by locking the controllable brakes to provide the isometric joint torques necessary during stance. The hybrid gait system was evaluated and compared to conventional four channel FES-aided gait using four subjects with paraplegia. The results demonstrated significant reduction in muscle fatigue and improvement in trajectory control when using the orthosis combined with FES compared to using FES alone. Results for distance and speed improvements varied across subjects. Considerable work remains in the design of the hardware before the system is feasible for use outside the laboratory.

Topics: Adult; Blood Pressure; Braces; Electric Stimulation Therapy; Equipment Design; Equipment Failure Analysis; Feasibility Studies; Female; Gait; Gait Disorders, Neurologic; Heart Rate; Hip Joint; Humans; Knee Joint; Male; Muscle Fatigue; Oxygen Consumption; Paraplegia; Pilot Projects; Spinal Cord Injuries; Torque; Treatment Outcome

The effects of long-term functional electrical stimulation (FES)-assisted walking on ankle dynamic stiffness were examined in spinal cord-injured (SCI) subjects with incomplete motor function loss. A parallel-cascade system identification method was used to identify intrinsic and reflex contributions to dynamic ankle stiffness at different ankle positions while subjects remained relaxed. Intrinsic stiffness dynamics were well modeled by a linear second-order model relating intrinsic torque to joint position. Reflex stiffness dynamics were accurately described by a linear third-order model relating halfwave rectified velocity to reflex torque. We examined four SCI subjects before and after long-term FES-assisted walking (> 16 mo). Another SCI subject, who used FES for only five months was examined 12 mo latter to serve as a non-FES, SCI control. Reflex stiffness decreased in FES subjects by an average of 53% following FES-assisted walking, intrinsic stiffness also dropped by 45%. In contrast, both reflex and intrinsic stiffness increased in the non-FES, SCI control. These findings suggest that FES-assisted walking may have therapeutic effects, helping to reduce abnormal joint stiffness.

Topics: Adult; Ankle Joint; Cervical Vertebrae; Chronic Disease; Elasticity; Electric Stimulation Therapy; Female; Follow-Up Studies; Gait Disorders, Neurologic; Humans; Longitudinal Studies; Lumbar Vertebrae; Male; Middle Aged; Models, Biological; Muscle Spasticity; Muscle, Skeletal; Range of Motion, Articular; Reflex, Stretch; Sensitivity and Specificity; Spinal Cord Injuries; Stress, Mechanical; Thoracic Vertebrae; Torque; Treatment Outcome; Walking

To measure spasticity of the knee flexors and extensor muscles in two different hip positions.. Swiss Paraplegic Center Nottwil, Switzerland.. Twenty spinal cord injured (SCI) patients with complete lesions were tested with a torque-velocity dynamometer in the following positions: (1) supine with a hip angle of 0 degrees; (2) sitting with a hip angle of 90 degrees. The excursion of the knee was measured for both positions using a goniometer. Two flexion/extension movements of the knee were performed at a speed of 10 degrees per sec. A further four flexion/extension movements over the same trajectory were made at a speed of 120 degrees per sec. Eccentric peak torques were measured continuously during movement of both legs for both speeds.. At a speed of 120 degrees per second, there was a significant difference in stretch reflex of the hamstrings and quadriceps femoris muscles for the two positions (Wilcoxon's paired t-test, P<0.05). Excitability was higher for the quadriceps femoris muscles in supine than in sitting position. For the hamstrings, the effect was reversed. Significant differences between sitting and supine position were not found for the speed of 10 degrees per sec. Test-retest reliability was high for the movements of 120 degrees per sec but low for 10 degrees per sec.. Our findings indicate that for a reliable and comparable measurement of spasticity, an exact description of test position and procedure is essential.

Topics: Adult; Cervical Vertebrae; Hip; Humans; Isotonic Contraction; Knee; Middle Aged; Muscle Spasticity; Muscle, Skeletal; Paralysis; Posture; Reflex, Stretch; Reproducibility of Results; Spinal Cord Injuries; Thoracic Vertebrae; Torque

To determine the effect of 4 weeks of 30 minutes of daily stretching on ankle mobility in patients with recent spinal cord injuries (SCIs).. Assessor-blinded randomized controlled trial.. Two spinal injury units in Sydney, Australia.. Consecutive sample of 14 recently injured patients with paraplegia and quadriplegia.. Treated ankles were stretched continuously into dorsiflexion with a torque of 7.5 N x m for 30 minutes each weekday for 4 weeks. Contralateral ankles received no stretches.. Passive torque-angle curves for both ankles were obtained at study commencement, then at weeks 2, 4, and 5 (ie, during, at the end of, and 1 week after the stretching program). Torque-angle measurements were obtained with the knee extended and flexed. Mean values for parameters (baseline angle, angle at 10 N x m, slope) describing the characteristics of the torque-angle curves were derived for each knee position. Changes from pretest to each subsequent test were calculated, as well as 95% confidence intervals (CIs) for differences in these changes between stretched and controlled ankles.. The stretching intervention did not significantly change any of the 3 parameters describing the torque-angle curves of the ankle in either knee position. At the beginning of the study, the mean (+/-SD) angles obtained with the application of a standardized torque with the knee extended for the control and stretch ankles were 105 degrees (+/- 10.4 degrees) and 106 degrees (+/- 9.8 degrees), respectively. After 4 weeks, these values were 106 degrees (+/- 10.6 degrees) and 107 degrees (+/- 10.6 degrees) (mean difference in change of angle = 0 degrees; 95% CI, -3.3 degrees to 3.3 degrees).. Thirty minutes of daily stretching for 4 weeks does not significantly change ankle mobility in recently injured patients with SCIs.

Topics: Adult; Ankle Joint; Biomechanical Phenomena; Contracture; Humans; Male; Paraplegia; Quadriplegia; Range of Motion, Articular; Rehabilitation; Spinal Cord Injuries; Statistics, Nonparametric; Torque

A study of the impact of spinal cord injury (SCI) on seated balance was conducted by comparing the results obtained from experiments with able-bodied and SCI subjects.. The purpose of this preliminary study was to examine the lateral postural stability of seated individuals with SCI in a dynamic environment.. Experiments were conducted at the Cleveland Clinic Foundation in Cleveland, Ohio.. Controlled perturbations were applied to each subject, seated in a wheelchair, through the use of a servo-controlled tilt platform. The platform was rotated so as to create disturbances similar in nature to those experienced in the frontal plane during left turns in a vehicle. Four quadriplegic, four paraplegic, and five able-bodied subjects participated in this study. Kinematic information and center of pressure (COP) movement were recorded.. None of the spinal cord-injured subjects was able to maintain his stability when exposed to the stronger perturbations, while all of the able-bodied subjects stayed upright for all of the trials. On an individual basis, injury level was not always indicative of balance. However, regression results suggest a correlation between ability to perform static leaning and dynamic balance (P<0.001).. SCI subjects lost stability under dynamic conditions even though they were stable in the static situation. Initial results also raise some questions about where and when external support may be needed. Information of this nature could help to guide the design of new lateral supports with improved client acceptance.

Topics: Adult; Algorithms; Biomechanical Phenomena; Humans; Male; Paraplegia; Postural Balance; Posture; Quadriplegia; Spinal Cord Injuries; Torque; Wheelchairs

The aim of this study was to determine the effect of the time after spinal cord injury (less than and greater than 10 months) on the mechanical and electrophysiological characteristics of muscle fatigue of the paralyzed electrically stimulated quadriceps muscle. Morphologically and histochemically, a relationship was observed between muscle fatigue and the delay from injury, revealing a critical period of enzymatic turning and a maximum peak of atrophy around the 10th month after the injury, followed by a long-term stabilization. Knee-torque output and M-wave variables (amplitude, latency, duration, and root mean square, RMS) of two muscular heads of the quadriceps were recorded in 19 paraplegic patients during a 120-s isometric contraction. The fatiguing muscle contraction was elicited by supramaximal continuous 20-Hz electrical stimulation. Compared to the chronic group, the acutely paralyzed group showed a greater resistance to fatigue (amount and rate of force decline, P < or = 0.01), smaller alterations of the M-wave amplitude and RMS, and a limited decrease of the muscle fiber conduction velocity (P < 0.05). Mechanical and electrophysiological changes during fatigue provided a clear functional support of the transformation of skeletal muscle under the lesion and of the existence of a critical period of muscular turn. In conclusion, when considering the artificial restoration of motor function, the evolution of the endurance and force-generating capabilities of the muscle actuator must be taken into account, particularly when tasks require important safety conditions (e.g., standing and walking).

Topics: Adult; Algorithms; Electrophysiology; Female; Humans; Knee; Male; Middle Aged; Models, Biological; Muscle Fatigue; Muscle, Skeletal; Paralysis; Spinal Cord Injuries; Time Factors; Torque

To determine the value of isokinetic dynamometric measurement of passive resistance in quantifying spasticity.. Turkey.. Thirty-three spastic spinal cord-injured patients and 14 age-matched normal individuals were studied. Five consecutive flexion-extensions of the knee, abduction-adductions of the hip, and dorsal-plantar flexions of the ankle were performed at specific velocities (15, 30, 60, 90 and 120 degrees /s) using a computerized isokinetic dynamometer set at the continuous passive motion mode. We recorded maximum torque and the sum of torque amplitudes for five repetitions of each type of joint motion at all velocities.. Maximum torque values and the sum of torque amplitudes were both significantly higher in spastic patients than in controls, and there was a positive correlation between torque values and Ashworth scores. There was no significant linear increase in torque values associated with increasing velocity for any of the motions in either controls or patients.. Isokinetic dynamometric measurement of passive resistance appeared to be a valuable tool for assessing and quantifying spasticity, as well as other types of hypertonus.

Topics: Adult; Ankle; Female; Hip; Humans; Knee; Male; Manometry; Movement; Muscle Contraction; Muscle Spasticity; Muscle, Skeletal; Spinal Cord Injuries; Torque

An adaptive feedforward control system has been evaluated for use in functional neuromuscular stimulation (FNS) systems. The control system, which utilizes neural network techniques, was used to generate isometric muscle contractions to track a periodic torque trajectory signal. The evaluation of the control system was performed using percutaneous intramuscular electrodes to stimulate the quadriceps muscles of spinal cord injured adolescents. Results of the evaluation indicate that the control system automatically customized its parameters for controlling isometric muscle torque in a particular muscle and that the parameters were adapted on-line to account for changes in muscle properties due to fatigue. This study demonstrates that this control system may play an important role in the development of practical FNS systems that are capable of automatically adjusting stimulation parameters to fit the needs of a particular individual at a given time.

Topics: Adaptation, Physiological; Adolescent; Electric Stimulation Therapy; Feedback; Humans; Isometric Contraction; Muscle Fatigue; Neural Networks, Computer; Recruitment, Neurophysiological; Spinal Cord Injuries; Torque

One of the major challenges facing functional electrical stimulation (FES) cycling is the design of an automatic control system that addresses the problem of disturbance with unknown bound and time-varying behavior of the muscular system. The previous methods for FES-cycling are based on the system modeling and require pre-adjustment of the control parameters which are based on the model parameters. These will degrade the FES-cycling performance and limit the clinical application of the methods. In this paper, a distributed cooperative control framework, which is based on an adaptive higher-order sliding mode (AHOSM) controller, is proposed for simultaneous control of torque and cadence in FES-cycling. The proposed control system is free-model which does not require any pre-adjustment of the control parameters and does not need the boundary of the disturbance to be known. Another major issue in FES-cycling is the stimulation pattern. In the paper, an automatic pattern generator is proposed which is capable of providing not only the regions of the crank angle in which each muscle group should be stimulated but also a specific gain for each muscle group. The results of the simulation studies and experiments on three spinal cord injuries showed that the proposed control strategy significantly increases the efficiency and tracking accuracy of motor-assisted FES-cycling in paraplegic patients and decreases the power consumption compared to HOSM controller with the fixed stimulation pattern. Reducing power consumption can slow down muscle fatigue and consequently increase cycling endurance. The average of cadence and torque tracking errors over three subjects using the proposed method are 5.77± 0.5% and 5.23± 0.8%, respectively.

Topics: Bicycling; Electric Stimulation; Electric Stimulation Therapy; Humans; Paraplegia; Spinal Cord Injuries; Torque

Spinal cord injury (SCI) affects a large number of individuals in the United States. Unfortunately, traditional neurorehabilitation therapy leaves out clinical populations with limited motor function, such as severe stroke or spinal cord injury, as they are incapable of engaging in movement therapy. To increase the numbers of individuals who may be able to participate in robotic therapy, our long-term goal is to combine two validated interventions, transcutaneous spinal stimulation (TSS) and robotics, to elicit upper limb movements during rehabilitation following SCI. To achieve this goal, it is necessary to quantify the contributions of each intervention to realizing arm movements. Electromyography is typically used to assess the response to TSS, but the robot itself offers an additional source of data since the available sensors on the robot can be used to directly assess resultant actions of the upper limb after stimulation. We explore this approach in this paper. We showed that the effects of cutaneous TSS can be observed by measuring the holding torque required by the exoskeleton to keep a user's arm in a neutral position. Further, we can identify differences in resultant action based on the location of the stimulation electrodes with respect to the dorsal roots of the spinal cord. In the future, we can use measurements from the robot to guide the action of the robot and TSS intervention.

Topics: Exoskeleton Device; Humans; Robotics; Spinal Cord Injuries; Torque; Upper Extremity

Individuals who suffer from paralysis as a result of a spinal cord injury list restoration of arm and hand function as a top priority. FES helps restore movement using the user's own muscles, but does not produce accurate and repeatable movements necessary for many functional tasks. Robots can assist users in achieving accurate and repeatable movements, but often require bulky hardware to generate the necessary torques. We propose sharing torque requirements between a robot and FES to reduce robot torque output compared to a robot acting alone, yet maintain high accuracy. Cooperative PD and model predictive control algorithms were designed to share the control between these two torque sources. Corresponding PD and MPC algorithms that do not use FES were also designed. The control algorithms were tested with 10 able-bodied subjects. Torque and position tracking accuracy were compared when the system was commanded to follow a functional elbow flexion/extension trajectory. The robot torque required to achieve these movements was reduced for the shared control cases compared to the algorithms acting without FES. We observed a reduction in position accuracy with the MPC shared controller compared to the PD shared controller, while the MPC shared controller resulted in greater reductions in torque requirements. Both of these shared algorithms showed improvements over existing options, and can be used on any given trajectory, allowing for better transferability to functional tasks.

Topics: Elbow; Electric Stimulation; Exoskeleton Device; Humans; Movement; Spinal Cord Injuries; Torque

Surface EMG-driven modelling has been proposed as a means to control assistive devices by estimating joint torques. Implanted EMG sensors have several advantages over wearable sensors but provide a more localized information on muscle activity, which may impact torque estimates. Here, we tested and compared the use of surface and intramuscular EMG measurements for the estimation of required assistive joint torques using EMG driven modelling.. Four healthy subjects and three incomplete spinal cord injury (SCI) patients performed walking trials at varying speeds. Motion capture marker trajectories, surface and intramuscular EMG, and ground reaction forces were measured concurrently. Subject-specific musculoskeletal models were developed for all subjects, and inverse dynamics analysis was performed for all individual trials. EMG-driven modelling based joint torque estimates were obtained from surface and intramuscular EMG.. The correlation between the experimental and predicted joint torques was similar when using intramuscular or surface EMG as input to the EMG-driven modelling estimator in both healthy individuals and patients.. We have provided the first comparison of non-invasive and implanted EMG sensors as input signals for torque estimates in healthy individuals and SCI patients.. Implanted EMG sensors have the potential to be used as a reliable input for assistive exoskeleton joint torque actuation.

Topics: Electromyography; Humans; Muscle, Skeletal; Muscles; Spinal Cord Injuries; Torque; Walking

The study aimed to assess the long-term persistent symptoms of patients with diabetes mellitus (DM) and COVID-19 infection at 9 months after acute infection.. This single-center cross-sectional study was conducted from May 20 to June 1, 2021.. Long-term persistent symptoms of COVID-19 infection are common among patients with DM.. The present study showed that the methanolic leaf extract and solvent fractions of. Acute arm eccentric exercise did not influence antibody titers or cell mediated immune responses to the influenza vaccine delivered post-exercise in older adults. More strenuous exercise may be required for exercise to act as an adjuvant. ClinicalTrials.gov Identifier: NCT03736759.

Topics: Adolescent; Adult; Aged; Animals; Anti-HIV Agents; Antiretroviral Therapy, Highly Active; Area Under Curve; CD4 Lymphocyte Count; Child; Child, Preschool; Chromatography, High Pressure Liquid; Chronic Disease; Cross-Sectional Studies; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Drug Interactions; Ethiopia; Female; France; Hand Strength; Healthcare Disparities; HIV Infections; Humans; Infant; Inhibitory Concentration 50; Intermittent Urethral Catheterization; Male; Mass Screening; Microsomes, Liver; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Nevirapine; Pharmaceutical Preparations; Predictive Value of Tests; Primary Health Care; Prognosis; Proportional Hazards Models; Protein Kinase Inhibitors; Pyrimidines; Quality of Life; Rats; Rats, Sprague-Dawley; Reproducibility of Results; Retrospective Studies; Risk Factors; Social Support; Spinal Cord Injuries; Surveys and Questionnaires; Tandem Mass Spectrometry; Time Factors; Time-to-Treatment; Torque; Transients and Migrants; Treatment Failure; Urinary Bladder, Neurogenic; Young Adult

Functional electrical stimulation (FES) is commonly used in rehabilitation to generate electrically-induced muscle contractions. FES has been shown to assist in the recovery of voluntary motor functions after stroke or spinal cord injury. However, discomfort associated with FES can motivate patients to withdraw their participation from FES therapy despite its benefits. To address this issue, a functional electrical stimulator, called MyndMove™ (MyndTec Inc., Canada), has been developed to generate more comfortable contractions than conventional stimulators.. Cross-sectional, interventional, with two treatment arms.. A laboratory within a rehabilitation center.. Twelve able-bodied participants.. FES delivered with two different stimulators, MyndMove™ and Compex Motion (Compex, Switzerland), during muscle contractions of high, moderate and low stimulation intensity.. Comfort-related preference to a given stimulator and the discomfort score rated through a Numeric Rating Scale (NRS-101) for both stimulators.. Participants perceived a reduction in discomfort during high-intensity stimulation generated using MyndMove™. In addition, MyndMove™ stimulations were preferred in 60% of all contractions. The reduction in discomfort associated with MyndMove™ might be due the fact that MyndMove™ delivers less charge to generate contractions of equivalent intensity, compared to Compex Motion.. Reducing discomfort during FES may help in generating stronger and more clinically useful contractions, increasing accessibility of FES therapy to include individuals with low tolerance to FES.

Topics: Cross-Sectional Studies; Electric Stimulation; Electric Stimulation Therapy; Humans; Muscle Contraction; Muscle, Skeletal; Spinal Cord Injuries; Torque

Determine trunk and shoulder muscle strength cutoff points for functional independence and wheelchair skills, and verify the predictive capacity of relative and absolute peak torque in men with spinal cord injury (SCI).. Cross-sectional study.. Rehabilitation hospital setting.. Men (N=54) with SCI were recruited and stratified into high and low paraplegia groups.. All participants performed maximum strength tests for shoulder abduction or adduction (isokinetic) and trunk flexion or extension (isometric) to determine relative and absolute peak torque cutoff points for the Spinal Cord Independence Measure version III (SCIM-III) and Adapted Manual Wheelchair Circuit (AMWC).. The primary outcome measures were SCIM-III, AMWC-Brazil test, and strength variables (peak torques). Demographic characteristics obtained from participants' electronic medical records were the secondary outcomes used as predictor variables of functional independence.. The best predictive model for SCIM-III (R=0.78, P≤.05) used the sum of trunk flexion and extension relative peak torque values to determine the cutoff points (1.42 N·m/kg for a score of 70). Relative shoulder abduction peak torque was used in the predictive models for AMWC outcomes: performance score (R=0.77, P≤.05, cutoff points of 0.97 N·m/kg for 300.0m) and 3-minute overground wheeling (R=0.72, P≤.05, cutoff points of 0.96 N·m/kg for 18.5s).. Relative peak torque showed better predictive capacity compared to absolute peak torque. Cutoff points were established for relative muscle strength and could help health professionals set appropriate goals for individuals with SCI to achieve high functional independence and wheelchair ability.

Topics: Adult; Cross-Sectional Studies; Disability Evaluation; Humans; Male; Muscle Strength; Muscle, Skeletal; Paraplegia; Shoulder; Spinal Cord Injuries; Thorax; Torque; Wheelchairs

Using traditional regression modelling, we have previously demonstrated a positive and strong relationship between paralyzed knee extensors' mechanomyographic (MMG) signals and neuromuscular electrical stimulation (NMES)-assisted knee torque in persons with spinal cord injuries. In the present study, a method of estimating NMES-evoked knee torque from the knee extensors' MMG signals using support vector regression (SVR) modelling is introduced and performed in eight persons with chronic and motor complete spinal lesions.. The model was developed to estimate knee torque from experimentally derived MMG signals and other parameters related to torque production, including the knee angle and stimulation intensity, during NMES-assisted knee extension.. When the relationship between the actual and predicted torques was quantified using the coefficient of determination (R. These results showed good predictive accuracy for SVR modelling, which can be generalized, and suggested that the MMG signals from paralyzed knee extensors are a suitable proxy for the NMES-assisted torque produced during repeated bouts of isometric knee extension tasks. This finding has potential implications for using MMG signals as torque sensors in NMES closed-loop systems and provides valuable information for implementing this method in research and clinical settings.

Topics: Electric Stimulation; Humans; Knee; Knee Joint; Muscle, Skeletal; Quadriceps Muscle; Spinal Cord Injuries; Torque

Individuals with incomplete spinal cord injury (iSCI) might show muscle fatigability during walking, primarily over long distances. The cause can be related to the motor impairment and walking compensations identified in this population. However, evidence on the occurrence of muscle fatigability after prolonged walking in individuals with iSCI is conflicting.. Does prolonged walking cause higher muscle fatigability in individuals with iSCI compared with matched-controls?. We adopted a repeated measures design, in which maximal voluntary isometric contractions were performed before and after a walking test to induce the fatigability, in 24 individuals with iSCI and 24 matched-controls. Body weight-normalized peak torque (PT/BW), rate of force development (RFD), root mean square (RMS) and neuromuscular efficiency were used to assess the muscle fatigability. A mixed model ANOVA (2 × 2) was used for between-group and within-group comparisons. The significance was set in 5%.. Individuals with iSCI showed a greater decline in the PT/BW and RMS after the walking test. However, the RFD presented a greater decrease in the control group.. Our results showed that prolonged walking caused higher muscle fatigability in individuals with iSCI compared to healthy individuals. Therefore, muscle fatigability should be considered during the rehabilitation planning and in activities of daily living of individuals with iSCI. Moreover, the identification of muscle fatigability in individuals with iSCI might be useful to prevent high levels of physical exertion and, possibly, the risk of fall.

Topics: Adult; Case-Control Studies; Cross-Sectional Studies; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle Fatigue; Muscle, Skeletal; Physical Exertion; Spinal Cord Injuries; Torque; Walking

Functional electrical stimulation (FES) has been used to produce force-related activities on the paralyzed muscle among spinal cord injury (SCI) individuals. Early muscle fatigue is an issue in all FES applications. If not properly monitored, overstimulation can occur, which can lead to muscle damage. A real-time mechanomyography (MMG)-based FES system was implemented on the quadriceps muscles of three individuals with SCI to generate an isometric force on both legs. Three threshold drop levels of MMG-root mean square (MMG-RMS) feature (thr50, thr60, and thr70; representing 50%, 60%, and 70% drop from initial MMG-RMS values, respectively) were used to terminate the stimulation session. The mean stimulation time increased when the MMG-RMS drop threshold increased (thr50: 22.7 s, thr60: 25.7 s, and thr70: 27.3 s), indicating longer sessions when lower performance drop was allowed. Moreover, at thr70, the torque dropped below 50% from the initial value in 14 trials, more than at thr50 and thr60. This is a clear indication of muscle fatigue detection using the MMG-RMS value. The stimulation time at thr70 was significantly longer (p = 0.013) than that at thr50. The results demonstrated that a real-time MMG-based FES monitoring system has the potential to prevent the onset of critical muscle fatigue in individuals with SCI in prolonged FES sessions.

Topics: Electric Stimulation Therapy; Humans; Muscle Contraction; Muscle Fatigue; Pilot Projects; Spinal Cord Injuries; Torque

What is the central question of this study? Spinal cord injury results in paralysis and deleterious neuromuscular and autonomic adaptations. Lumbosacral epidural stimulation can modulate motor and/or autonomic functions. Does long-term epidural stimulation for normalizing cardiovascular function affect leg muscle properties? What is the main finding and its importance? Leg lean mass increased after long-term epidural stimulation for cardiovascular function, which was applied in the sitting position and did not activate the leg muscles. Leg muscle strength and fatigue resistance, assessed in a subgroup of individuals, also increased. These adaptations might support interventions for motor recovery and warrant further mechanistic investigation.. Chronic motor complete spinal cord injury (SCI) results in paralysis and deleterious neuromuscular and autonomic adaptations. Paralysed muscles demonstrate atrophy, loss of force and increased fatigability. Also, SCI-induced autonomic impairment results in persistently low resting blood pressure and heart rate, among other features. We previously reported that spinal cord epidural stimulation (scES) optimized for cardiovascular (CV) function (CV-scES), which is applied in sitting position and does not activate the leg muscles, can maintain systolic blood pressure within a normotensive range during quiet sitting and during orthostatic stress. In the present study, dual-energy X-ray absorptiometry collected from six individuals with chronic clinically motor complete SCI demonstrated that 88 ± 11 sessions of CV-scES (7 days week

Topics: Adaptation, Physiological; Adult; Cardiovascular System; Epidural Space; Female; Humans; Leg; Male; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Paralysis; Spinal Cord; Spinal Cord Injuries; Spinal Cord Stimulation; Torque; Young Adult

To compare a standardized submaximal intensity (based on the rate of perceived exertion [RPE]) with the percentage of the average and peak torque during a familiarization session in individuals with different spinal cord injury (SCI) levels in gravity-resisted and gravity-assisted movements.. This was a cross-sectional study at a rehabilitation hospital. Thirty-six individuals stratified in tetraplegia (TP), high paraplegia (HP), and low paraplegia (LP) groups and 12 matched control participants (CG) were enrolled in the study. Participants performed a maximum strength test using isokinetic dynamometry. The familiarization consisted of 10 submaximal repetitions with a level 2 (i.e., 20% of the maximum score) in the Resistance Exercise Scale (OMNI-RES). Fisher's exact test compared the percentages of the average torque (%AT. The %AT. Different RPE levels should be adopted for gravity-resisted or gravity-assisted upper limb exercises to maintain the same relative intensity during a familiarization session.

Topics: Adult; Cross-Sectional Studies; Exercise Test; Humans; Male; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Physical Exertion; Spinal Cord Injuries; Torque; Upper Extremity; Young Adult

Although advances in technology promoted new physiotherapy approaches, there is still an urge for equipment and techniques to improve the quality of patients lives with motor disabilities. Functional electrical stimulation cycling (FES cycling) is an example of this type of technology, in which the control of stimulation parameters enables a spinal cord injured person to ride a bicycle. In this work, we aim to investigate the use of passive knee orthoses for FES cycling assistance. Hence, we compared the cycling cadence and quadriceps excitation using an FES cycling simulation platform for different spring torques and ranges. In this paper, we obtained spring parameters that increased cycling cadence by 10.60% while decreasing by 7.33% the quadriceps activity, which indicates that this type of passive orthosis may diminish fatigue caused by FES.

Topics: Bicycling; Electric Stimulation Therapy; Humans; Orthotic Devices; Quadriceps Muscle; Spinal Cord Injuries; Torque

After spinal cord injury (SCI), hybrid stimulation patterns that interpose paired-pulse doublets over a constant-frequency background may enhance the metabolic "work" (muscle torque) performed by paralyzed muscle. This study examined the effect of background stimulation frequency on the torque contribution of the doublet before and after fatigue.. Cross-sectional study.. Research laboratory in an academic medical center.. Five men with chronic sensory and motor-complete SCI and ten non-SCI controls (6 males, 4 females). SCI subjects were recruited from a long-term study of unilateral plantar-flexor training; both limbs were tested for the present study.. Subjects underwent plantar flexor stimulation at 5, 7, 9, and 12 Hz. The four background frequencies were overlaid with 6 ms doublets delivered at the start, middle, or at both the start and middle of each train. The 5 Hz and 12 Hz frequencies were analyzed after fatigue.. Mean torque, peak torque, torque fusion index, doublet torque.. Trains with doublets at both the start and middle yielded the most consistent enhancement of torque (all P < 0.028). Torque contribution of the doublet was greatest at low stimulus frequencies (all P < 0.016). The low relative fusion of untrained paralyzed muscle preserved the efficacy of the doublet even during fatigue.. Hybrid stimulus trains may be an effective way to increase contractile work in paralyzed muscle, even after fatigue. They may be useful for rehabilitation strategies designed to enhance the metabolic work performed by paralyzed skeletal muscle.

Topics: Adult; Electric Stimulation Therapy; Female; Humans; Male; Muscle, Skeletal; Paralysis; Spinal Cord Injuries; Torque

Strength training is one of the most common interventions employed to increase functional independence during rehabilitation of individuals with spinal cord injury (SCI). However, in the literature, different results have been reported in terms of strength modifications after a SCI compared with a control group (CG).. This study aimed to verify whether discriminant analysis using relative and absolute strength is able to discriminate individuals with different levels of SCI from a CG and to compare strength values of men with different levels of SCI with a CG.. Cross-sectional study.. Rehabilitation hospital setting.. A total of 36 individuals with SCI stratified in tetraplegia (TP; C6-C8), high paraplegia (HP; T1-T6), and low paraplegia (LP; T7-L2), and 12 matched control subjects were enrolled in the study.. The subjects performed a maximum strength test of elbow extension/flexion and also shoulder abduction/adduction and flexion/extension in an isokinetic dynamometer. Discriminant analysis was carried out to identify which strength variables would be able to discriminate the TP, HP, or LP groups from the CG. A 1-way analysis of variance was performed to compare peak torque and agonist/antagonist ratio means.. Shoulder adduction, followed by elbow extension peak torque, was the best variable for discriminating the TP group from the CG (function coefficients: -0.056 and 0.051, respectively, Wilks Λ = 0.41, P ≤ .05). There were no significant differences between the HP group, LP group, and CG.. The strength similarity of the paraplegic groups and the CG should not be extrapolated for activities of daily living or sports. The TP group demonstrated lower peak torque for all movements than the CG.

Topics: Adult; Cross-Sectional Studies; Discriminant Analysis; Elbow; Humans; Male; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Paraplegia; Quadriplegia; Shoulder; Spinal Cord Injuries; Torque; Young Adult

Spinal cord injury (SCI) results in deleterious skeletal muscle adaptations, such as relevant atrophy and loss of force. In particular, the relevant loss of lower-limb force-generating capacity may limit functional mobility even if neuronal control was sufficient. Currently, methods of assessing maximal force-generating capacity using neuromuscular electrical stimulation (NMES) are limited in individuals who cannot tolerate higher stimulation amplitudes, such as those with residual sensation and those at risk of fracture. In this study, we examined the relationship between NMES amplitude and muscle torque exerted (recruitment curve) in order to determine whether maximal torque output can be characterized by a submaximal marker. Recruitment curves for knee extensors, knee flexors, and ankle plantarflexors were recorded from 30 individuals with motor complete SCI. NMES was delivered starting with an amplitude of 5 mA, and increasing by 5 mA for every subsequent stimulation until either the participant requested to stop the stimulation or the maximum stimulation amplitude (140 mA) was reached. Significant correlations between peak slope of the recruitment curve and peak torque for all muscle groups were found (knee extensors, r = 0.75; p < 0.0001; knee flexors, r = 0.68; p < 0.0001; ankle plantarflexors, r = 0.91; p < 0.0001), indicating that muscles that show greater peak slope of the recruitment curve tend to generate a greater peak torque. This suggests that peak slope, which was achieved at an average stimulation intensity (55.0 mA) that was 43% smaller than that corresponding to peak torque (97.4 mA), may be used as a submaximal marker for characterizing maximal torque output in individuals with SCI.

Topics: Adult; Electric Stimulation; Female; Humans; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Paralysis; Spinal Cord Injuries; Torque

Neuromuscular electrical stimulation (NMES) is commonly used in skeletal muscles in people with spinal cord injury (SCI) with the aim of increasing muscle recruitment and thus muscle force production. NMES has been conventionally used in clinical practice as functional electrical stimulation (FES), using low levels of evoked force that cannot optimally stimulate muscular strength and mass improvements, and thus trigger musculoskeletal changes in paralysed muscles. The use of high intensity intermittent NMES training using wide-pulse width and moderate-intensity as a strength training tool could be a promising method to increase muscle force production in people with SCI. However, this type of protocol has not been clinically adopted because it may generate rapid muscle fatigue and thus prevent the performance of repeated high-intensity muscular contractions in paralysed muscles. Moreover, superimposing patellar tendon vibration onto the wide-pulse width NMES has been shown to elicit further increases in impulse or, at least, reduce the rate of fatigue in repeated contractions in able-bodied populations, but there is a lack of evidence to support this argument in people with SCI.. Nine people with SCI received two NMES protocols with and without superimposing patellar tendon vibration on different days (i.e. STIM and STIM+vib), which consisted of repeated 30 Hz trains of 58 wide-pulse width (1000 μs) symmetric biphasic pulses (0.033-s inter-pulse interval; 2 s stimulation train; 2-s inter-train interval) being delivered to the dominant quadriceps femoris. Starting torque was 20% of maximal doublet-twitch torque and stimulations continued until torque declined to 50% of the starting torque. Total knee extensor impulse was calculated as the primary outcome variable.. Total knee extensor impulse increased in four subjects when patellar tendon vibration was imposed (59.2 ± 15.8%) but decreased in five subjects (- 31.3 ± 25.7%). However, there were no statistically significant differences between these sub-groups or between conditions when the data were pooled.. Based on the present results there is insufficient evidence to conclude that patellar tendon vibration provides a clear benefit to muscle force production or delays muscle fatigue during wide-pulse width, moderate-intensity NMES in people with SCI.. ACTRN12618000022268 . Date: 11/01/2018. Retrospectively registered.

Topics: Adult; Electric Stimulation Therapy; Female; Humans; Male; Muscle Contraction; Muscle Fatigue; Muscle Strength; Patellar Ligament; Quadriceps Muscle; Resistance Training; Spinal Cord Injuries; Torque; Vibration

Topics: Adult; Electromyography; Humans; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Spinal Cord Injuries; Torque

Muscle force production is usually impaired in people with spinal cord injury (SCI). The use of high-intensity neuromuscular electrical stimulation (NMES) strength training can help promote metabolically active lean muscle mass and, thus, increase muscle mass and improve physical health and quality of life (QoL). Nonetheless, NMES is usually used at low-stimulation intensities, and there is limited evidence on the effects of high-intensity NMES strength training into improving muscle force and mass, symptoms of spasticity, or physical health and QoL in people with SCI.. Five individuals with chronic SCI completed five 10-repetition sets of high-intensity knee extension NMES strength training sessions for 12 wk in both quadriceps muscles. Quadriceps femoris (QF) knee extensor torque was measured on a dynamometer, and cross-sectional area (CSAQF) was measured with extended field-of-view ultrasonography. Venous blood samples were collected for blood lipid profiling and C-reactive protein analyses. The Spinal Cord Injury Spasticity Evaluation Tool was used to assess symptoms of spasticity, and the QoL index SCI version III was used for QoL measures.. QF tetanic knee extensor torque increased on average by 35% (2%-92%), and CSAQF increased by 47% (14%-145%). A significant increase in the HDL/LDL cholesterol ratio (P < 0.001) and a mean significant improvement of 4.8% ± 2.3% (absolute value = 0.26) in the Spinal Cord Injury Spasticity Evaluation Tool score was observed, whereas QoL showed a near-significant improvement in the health and functioning domain (15.0 ± 4.2 and 17.3 ± 5.1; P = 0.07).. High-intensity NMES strength training in people with SCI may improve muscle strength, mass, physical health, and QoL. However, replication of these results is necessary before clinical implementation.

Topics: Biomarkers; Electric Stimulation Therapy; Female; Humans; Lipids; Male; Muscle Strength; Muscle Strength Dynamometer; Quadriceps Muscle; Quality of Life; Resistance Training; Spinal Cord Injuries; Torque

Investigation of muscle fatigue during functional electrical stimulation (FES)-evoked exercise in individuals with spinal cord injury using dynamometry has limited capability to characterize the fatigue state of individual muscles. Mechanomyography has the potential to represent the state of muscle function at the muscle level. This study sought to investigate surface mechanomyographic responses evoked from quadriceps muscles during FES-cycling, and to quantify its changes between pre- and post-fatiguing conditions in individuals with spinal cord injury.. Six individuals with chronic motor-complete spinal cord injury performed 30-min of sustained FES-leg cycling exercise on two days to induce muscle fatigue. Each participant performed maximum FES-evoked isometric knee extensions before and after the 30-min cycling to determine pre- and post- extension peak torque concomitant with mechanomyography changes.. Similar to extension peak torque, normalized root mean squared (RMS) and mean power frequency (MPF) of the mechanomyography signal significantly differed in muscle activities between pre- and post-FES-cycling for each quadriceps muscle (extension peak torque up to 69%; RMS up to 80%, and MPF up to 19%). Mechanomyographic-RMS showed significant reduction during cycling with acceptable between-days consistency (intra-class correlation coefficients, ICC = 0.51-0.91). The normalized MPF showed a weak association with FES-cycling duration (ICC = 0.08-0.23). During FES-cycling, the mechanomyographic-RMS revealed greater fatigue rate for rectus femoris and greater fatigue resistance for vastus medialis in spinal cord injured individuals.. Mechanomyographic-RMS may be a useful tool for examining real time muscle function of specific muscles during FES-evoked cycling in individuals with spinal cord injury.

Topics: Adult; Electric Stimulation Therapy; Exercise Therapy; Female; Humans; Knee Joint; Male; Middle Aged; Muscle Fatigue; Myography; Quadriceps Muscle; Spinal Cord Injuries; Torque

A mechanomyography muscle contraction (MC) sensor, affixed to the skin surface, was used to quantify muscle tension during repetitive functional electrical stimulation (FES)-evoked isometric rectus femoris contractions to fatigue in individuals with spinal cord injury (SCI). Nine persons with motor complete SCI were seated on a commercial muscle dynamometer that quantified peak torque and average torque outputs, while measurements from the MC sensor were simultaneously recorded. MC-sensor-predicted measures of dynamometer torques, including the signal peak (SP) and signal average (SA), were highly associated with isometric knee extension peak torque (SP: r = 0.91,

Topics: Electric Stimulation; Humans; Isometric Contraction; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Spinal Cord Injuries; Torque

A spinal cord injury (SCI) frequently results in impaired balance, endurance, and strength with subsequent limitations in functional mobility and community participation. The purpose of this case report was to implement a training program for an individual with a chronic incomplete SCI using a novel divided-attention stepping accuracy task (DASAT) to determine if improvements could be made in impairments, activities, and participation. The client was a 51-year-old male with a motor incomplete C4 SCI sustained 4 years prior. He presented with decreased quality of life (QOL) and functional independence, and deficits in balance, endurance, and strength consistent with central cord syndrome. The client completed the DASAT intervention 3 times per week for 6 weeks. Each session incorporated 96 multi-directional steps to randomly-assigned targets in response to 3-step verbal commands. QOL, measured using the SF-36, was generally enhanced but fluctuated. Community mobility progressed from close supervision to independence. Significant improvement was achieved in all balance scores: Berg Balance Scale by 9 points [Minimal Detectable Change (MDC) = 4.9 in elderly]; Functional Reach Test by 7.62 cm (MDC = 5.16 in C5/C6 SCI); and Timed Up-and-Go by 0.53 s (MDC not established). Endurance increased on the 6-Minute Walk Test, with the client achieving an additional 47 m (MDC = 45.8 m). Lower extremity isokinetic peak torque strength measures were mostly unchanged. Six minutes of DASAT training per session provided an efficient, low-cost intervention utilizing multiple trials of variable practice, and resulted in better performance in activities, balance, and endurance in this client.

Topics: Attention; Biomechanical Phenomena; Cervical Vertebrae; Chronic Disease; Dependent Ambulation; Exercise Test; Exercise Tolerance; Humans; Male; Middle Aged; Mobility Limitation; Motor Activity; Muscle Strength; Physical Therapy Modalities; Postural Balance; Quality of Life; Recovery of Function; Spinal Cord Injuries; Torque; Treatment Outcome

To examine whether differences in propulsion technique as a function of intraindividual variability occur as a result of shoulder pain and physical activity (PA) level in full-time manual wheelchair users (MWUs).. Observational study.. Research laboratory.. Adults (N=14) with spinal cord injury (mean age: 30.64±11.08) who used a wheelchair for >80% of daily ambulation and were free of any condition that could be worsened by PA.. Not applicable.. PA level was measured using the Physical Activity Scale for Individuals with Physical Disabilities (PASIPD), and shoulder pain was measured using the Wheelchair User's Shoulder Pain Index (WUSPI) survey. Mean and intraindividual variability propulsion metrics were measured for propulsion analysis.. WUSPI scores indicated participants experienced low levels of shoulder pain. The results of the Spearman rank-order correlation revealed that PASIPD scores were significantly related to mean contact angle (r. Differences in propulsion technique were observed on the basis of PA levels. Participants with higher PASIPD scores used a more injurious stroke technique when propelling at higher speeds. This may indicate that active individuals who use injurious stroke mechanics may be at higher risk of injury. A strong relation was found between peak propulsion forces and shoulder pain. Rehabilitation professionals should emphasize the use of a protective stroke technique in both inactive and active MWUs during exercise and faster propulsion.

Topics: Adult; Biomechanical Phenomena; Exercise; Exercise Test; Female; Humans; Male; Middle Aged; Shoulder Pain; Spinal Cord Injuries; Torque; Wheelchairs; Young Adult

Neuromuscular electrical stimulation (NMES) over a muscle belly (mNMES) recruits superficial motor units (MUs) preferentially, whereas NMES over a nerve trunk (nNMES) recruits MUs evenly throughout the muscle. We performed tests to determine whether "interleaving" pulses between the mNMES and nNMES sites (iNMES) reduces the fatigability of contractions for people experiencing paralysis because of chronic spinal cord injury.. Plantar flexion torque and soleus electromyography (M-waves) were recorded from 8 participants. A fatigue protocol (75 contractions; 2 s on/2 s off for 5 min) was delivered by iNMES. The results were compared with previously published data collected with mNMES and nNMES in the same 8 participants.. Torque declined ∼40% more during mNMES than during nNMES or iNMES. M-waves declined during mNMES but not during nNMES or iNMES.. To reduce fatigability of electrically evoked contractions of paralyzed plantar flexors, iNMES is equivalent to nNMES, and both are superior to mNMES. Muscle Nerve 56: 989-993, 2017.

Topics: Adult; Biophysics; Electric Stimulation; Electromyography; Fatigue; Female; Humans; Male; Middle Aged; Muscle Contraction; Neuromuscular Junction; Recruitment, Neurophysiological; Spinal Cord Injuries; Torque; Treatment Outcome

After spinal cord injury (SCI), the antagonist muscles activation is increased during voluntary contractions and reflex conditioning protocols. This increase can be the result of both muscle atrophy and reciprocal facilitation mechanism. It remains however unclear to what extent increased antagonist muscles activation could be rather attributable to central vs. peripheral changes during voluntary contractions achieved by SCI participants.. We investigated the activations of elbow extensors and flexors during isometric elbow flexion and extension contractions performed at 3 force levels by 10 healthy participants and 8 participants with cervical SCI (cSCI).. At similar force level and absolute net torque in flexion, the antagonist muscles activation was increased for the participants with cSCI. At similar absolute net torque in extension, the activations of agonist and antagonist muscles were increased for the participants with cSCI.. During flexion contractions, increased antagonist muscles activation may be explained by extensors atrophy or reciprocal facilitation. During extension contractions, increased antagonist muscles activation may reflect the importance of reciprocal facilitation as antagonist muscles were evaluated as intact by clinical testing and maximal net joint torque recording.. These results in cSCI participants revealed an increased activation of antagonist muscles, which may reflect a reorganization of the spinal reflexes and their supraspinal control involved during isometric elbow contractions.

Topics: Adult; Cervical Vertebrae; Elbow Joint; Electromyography; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle, Skeletal; Spinal Cord Injuries; Torque

Although abnormal cutaneous reflex (CR) activity has been identified during gait after incomplete spinal cord injury (SCI), this activity has not been directly compared in subjects with and without the spasticity syndrome.. Characterisation of CR activity during controlled rest and 'ramp and hold' phases of controlled plantarflexion in subjects with and without the SCI spasticity syndrome.. Transverse descriptive study with non-parametric group analysis.. SCI rehabilitation hospital.. Tibialis Anterior (TA) reflexes were evoked by innocuous cutaneous plantar sole stimulation during rest and ramp and hold phases of plantarflexion torque in non-injured subjects (n=10) and after SCI with (n=9) and without (n=10) hypertonia and/or involuntary spasm activity. Integrated TA reflex responses were analysed as total (50-300 ms) or short (50-200 ms) and long-latency (200-300 ms) activity.. Total and long-latency TA activity was inhibited in non-injured subjects and the SCI group without the spasticity syndrome during plantarflexion torque but not in the SCI spasticity group. Furthermore, loss of TA reflex inhibition during plantarflexion correlated with time after SCI (ρ=0.79, P=0.009). Moreover, TA reflex activity inversely correlated with maximum plantarflexion torque in the spasticity group (ρ=-0.75, P=0.02), despite similar non-reflex TA electromyographic activity during plantarflexion after SCI in subjects with (0.11, 0.08-0.13 mV) or without the spasticity syndrome (0.09, 0.07-0.12 mV).. This reflex testing procedure supports previously published evidence for abnormal CR activity after SCI and may characterise the progressive disinhibition of TA reflex activity during controlled plantarflexion in subjects diagnosed with the spasticity syndrome.

Topics: Adult; Electromyography; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Spasticity; Muscle, Skeletal; Reaction Time; Reflex, Abnormal; Skin; Spinal Cord Injuries; Statistics, Nonparametric; Torque; Young Adult

The interaction between muscle contractions and joint loading produces torques necessary for movements during activities of daily living. However, during neuromuscular electrical stimulation (NMES)-evoked contractions in persons with spinal cord injury (SCI), a simple and reliable proxy of torque at the muscle level has been minimally investigated. Thus, the purpose of this study was to investigate the relationships between muscle mechanomyographic (MMG) characteristics and NMES-evoked isometric quadriceps torques in persons with motor complete SCI. Six SCI participants with lesion levels below C4 [(mean (SD) age, 39.2 (7.9) year; stature, 1.71 (0.05) m; and body mass, 69.3 (12.9) kg)] performed randomly ordered NMES-evoked isometric leg muscle contractions at 30°, 60° and 90° knee flexion angles on an isokinetic dynamometer. MMG signals were detected by an accelerometer-based vibromyographic sensor placed over the belly of rectus femoris muscle. The relationship between MMG root mean square (MMG-RMS) and NMES-evoked torque revealed a very high association (R(2)=0.91 at 30°; R(2)=0.98 at 60°; and R(2)=0.97 at 90° knee angles; P<0.001). MMG peak-to-peak (MMG-PTP) and stimulation intensity were less well related (R(2)=0.63 at 30°; R(2)=0.67 at 60°; and R(2)=0.45 at 90° knee angles), although were still significantly associated (P≤0.006). Test-retest interclass correlation coefficients (ICC) for the dependent variables ranged from 0.82 to 0.97 for NMES-evoked torque, between 0.65 and 0.79 for MMG-RMS, and from 0.67 to 0.73 for MMG-PTP. Their standard error of measurements (SEM) ranged between 10.1% and 31.6% (of mean values) for torque, MMG-RMS and MMG-PTP. The MMG peak frequency (MMG-PF) of 30Hz approximated the stimulation frequency, indicating NMES-evoked motor unit firing rate. The results demonstrated knee angle differences in the MMG-RMS versus NMES-isometric torque relationship, but a similar torque related pattern for MMG-PF. These findings suggested that MMG was well associated with torque production, reliably tracking the motor unit recruitment pattern during NMES-evoked muscle contractions. The strong positive relationship between MMG signal and NMES-evoked torque production suggested that the MMG might be deployed as a direct proxy for muscle torque or fatigue measurement during leg exercise and functional movements in the SCI population.

Topics: Activities of Daily Living; Adult; Biomechanical Phenomena; Electric Stimulation; Female; Humans; Isometric Contraction; Male; Mechanical Phenomena; Middle Aged; Quadriceps Muscle; Signal Processing, Computer-Assisted; Spinal Cord Injuries; Torque

Functional electrical stimulation (FES) is a neuroprosthetic technique for restoring lost motor function of spinal cord injured (SCI) patients and motor-impaired subjects by delivering short electrical pulses to their paralyzed muscles or motor nerves. FES induces action potentials respectively on muscles or nerves so that muscle activity can be characterized by the synchronous recruitment of motor units with its compound electromyography (EMG) signal is called M-wave. The recorded evoked EMG (eEMG) can be employed to predict the resultant joint torque, and modeling of FES-induced joint torque based on eEMG is an essential step to provide necessary prediction of the expected muscle response before achieving accurate joint torque control by FES.. Previous works on FES-induced torque tracking issues were mainly based on offline analysis. However, toward personalized clinical rehabilitation applications, real-time FES systems are essentially required considering the subject-specific muscle responses against electrical stimulation. This paper proposes a wireless portable stimulator used for estimating/predicting joint torque based on real time processing of eEMG. Kalman filter and recurrent neural network (RNN) are embedded into the real-time FES system for identification and estimation.. Prediction results on 3 able-bodied subjects and 3 SCI patients demonstrate promising performances. As estimators, both Kalman filter and RNN approaches show clinically feasible results on estimation/prediction of joint torque with eEMG signals only, moreover RNN requires less computational requirement.. The proposed real-time FES system establishes a platform for estimating and assessing the mechanical output, the electromyographic recordings and associated models. It will contribute to open a new modality for personalized portable neuroprosthetic control toward consolidated personal healthcare for motor-impaired patients.

Topics: Electric Stimulation Therapy; Electromyography; Female; Humans; Male; Muscle, Skeletal; Neural Networks, Computer; Spinal Cord Injuries; Torque

Skeletal muscle exercise regulates several important metabolic genes in humans. We know little about the effects of environmental stress (heat) and mechanical stress (vibration) on skeletal muscle. Passive mechanical stress or systemic heat stress are often used in combination with many active exercise programs. We designed a method to deliver a vibration stress and systemic heat stress to compare the effects with active skeletal muscle contraction.. The purpose of this study is to examine whether active mechanical stress (muscle contraction), passive mechanical stress (vibration), or systemic whole body heat stress regulates key gene signatures associated with muscle metabolism, hypertrophy/atrophy, and inflammation/repair.. Eleven subjects, six able-bodied and five with chronic spinal cord injury (SCI) participated in the study. The six able-bodied subjects sat in a heat stress chamber for 30 minutes. Five subjects with SCI received a single dose of limb-segment vibration or a dose of repetitive electrically induced muscle contractions. Three hours after the completion of each stress, we performed a muscle biopsy (vastus lateralis or soleus) to analyze mRNA gene expression.. We discovered repetitive active muscle contractions up regulated metabolic transcription factors NR4A3 (12.45 fold), PGC-1α (5.46 fold), and ABRA (5.98 fold); and repressed MSTN (0.56 fold). Heat stress repressed PGC-1α (0.74 fold change; p < 0.05); while vibration induced FOXK2 (2.36 fold change; p < 0.05). Vibration similarly caused a down regulation of MSTN (0.74 fold change; p < 0.05), but to a lesser extent than active muscle contraction. Vibration induced FOXK2 (p < 0.05) while heat stress repressed PGC-1α (0.74 fold) and ANKRD1 genes (0.51 fold; p < 0.05).. These findings support a distinct gene regulation in response to heat stress, vibration, and muscle contractions. Understanding these responses may assist in developing regenerative rehabilitation interventions to improve muscle cell development, growth, and repair.

Topics: Adult; Case-Control Studies; Exercise; Gene Expression Regulation; Heat-Shock Response; Hot Temperature; Humans; Male; Muscle Contraction; Muscle, Skeletal; Spinal Cord Injuries; Stress, Mechanical; Stress, Physiological; Torque; Vibration; Young Adult

Ankle joint control plays an important role in independent walking. This study investigated the effects of robotic-assisted locomotor training on impaired ankle joint control in individuals with chronic incomplete spinal cord injury.. Sixteen individuals with incomplete spinal cord injury underwent 12 one-h sessions of robotic-assisted locomotor training for 4 weeks, while 16 individuals with incomplete spinal cord injury served as inactive controls. Changes in ankle control measures, torque and co-activation were evaluated during maximal voluntary contractions in dorsi- and plantar-flexion. Changes in walking performance measures using Timed Up and Go (TUG), 10-m walk (10MWT) and 6-min walk (6MWT) tests were evaluated at 2 time points: baseline and after 4 weeks.. Maximal voluntary contractions torque during both dorsi- and plantar-flexion contractions improved markedly in the robotic-assisted locomotor training group compared with baseline. Furthermore, after the training, co-activation during the dorsi-flexion maximal voluntary contractions decreased in the training group compared with controls. In addition, the training group significantly improved walking mobility (TUG) and speed (10MWT) compared with baseline. Finally, correlation analysis indicated a significant linear relationship between maximal voluntary contraction torques and walking performance measures.. These findings provide evidence that robotic-assisted locomotor training improves ankle joint control, which may translate into enhanced walking performance in individuals with chronic incomplete spinal cord injury.

Topics: Adult; Aged; Ankle; Ankle Joint; Female; Humans; Male; Middle Aged; Physical Therapy Modalities; Robotics; Spinal Cord Injuries; Torque

To better understand volitional force generation after chronic incomplete spinal cord injury (SCI), we examined muscle activation during single and repeated isometric, concentric, and eccentric knee extensor (KE) maximal voluntary contractions (MVCs).. Torque and electromyographic (EMG) activity were recorded during single and repeated isometric and dynamic KE MVCs in 11 SCI subjects. Central activation ratios (CARs) were calculated for all contraction modes in SCI subjects and 11 healthy controls.. SCI subjects generated greater torque, KE EMG, and CARs during single eccentric vs. isometric and concentric MVCs (all P < 0.05). Torque and EMG remained similar during repeated eccentric MVCs; however, both increased during repeated isometric (>25%) and concentric (>30%) MVCs.. SCI subjects demonstrated greater muscle activation during eccentric MVCs vs. isometric and concentric MVCs. This pattern of activation contrasts with the decreased eccentric activation demonstrated by healthy controls. Such information may aid development of novel rehabilitation interventions.

Topics: Action Potentials; Adult; Electric Stimulation; Electromyography; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Spinal Cord Injuries; Statistics as Topic; Torque

Neuromuscular electrical stimulation (NMES) has been shown to impart a number of health benefits and can be used to produce functional outcomes. However, one limitation of NMES is the onset of NMES-induced fatigue. Multi-channel asynchronous stimulation has been shown to reduce NMES-induced fatigue compared to conventional single-channel stimulation. However, in previous studies in man, the effect of stimulation frequency on the NMES-induced fatigue has not been examined for asynchronous stimulation. Low stimulation frequencies are known to reduce fatigue during conventional stimulation. Therefore, the aim of this study was to examine the fatigue characteristics of high- and low-frequency asynchronous stimulation as well as high- and low-frequency conventional stimulation. Experiments were performed in both able-bodied and spinal cord injured populations. Low frequency asynchronous stimulation is found to have significant fatigue benefits over high frequency asynchronous stimulation as well as high- and low-frequency conventional stimulation, motivating its use for rehabilitation and functional electrical stimulation (FES).

Topics: Adult; Biomechanical Phenomena; Electric Stimulation; Electromyography; Equipment Design; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Spinal Cord Injuries; Torque; Young Adult

Variable frequency trains (VFT) or train combinations have been suggested as useful strategies to offset the rapid fatigue induced by constant frequency trains (CFT) during electrical stimulation. However, most studies have been of short duration with limited functional application in those with spinal cord injury (SCI). We therefore tested force and fatigue in response to VFT, CFT, and combined patterns in strength training-like conditions (6-s contractions).. Ten SCI individuals underwent either CFT or VFT patterns until target torque was no longer produced and then switched immediately to the other pattern.. Target torque was reached more times when VFT was used first (VFT: 6.7 ± 0.8 vs. CFT: 3.5 ± 0.2 contractions, P < 0.05) and when it was followed by the CFT pattern (VFT-CFT: 10.3 ± 1.2 vs.. 6.9 ± 1.2 contractions, P < 0.05).. These findings suggest that for the same initial forces the VFT pattern is less fatiguing than CFT and that when combining train types, VFT should be used first.

Topics: Adult; Electric Stimulation; Electric Stimulation Therapy; Female; Humans; Isometric Contraction; Male; Muscle Fatigue; Quadriceps Muscle; Spinal Cord Injuries; Torque; Treatment Outcome

Cross-sectional study.. To determine the effect of injury duration on plantar-flexor elastic properties in individuals with chronic spinal cord injury (SCI) and spasticity.. National Rehabilitation Center for Persons with Disabilities, Japan.. A total of 16 chronic SCI patients (age, 33±9.3 years; injury localization, C6-T12; injury duration, 11-371 months) participated. Spasticity of the ankle plantar-flexors was assessed using the Modified Ashworth Scale (MAS). The calf circumference and muscle thickness of the medial gastrocnemius (MG), lateral gastrocnemius and soleus were assessed using tape measure and ultrasonography. In addition, the ankle was rotated from 10° plantar-flexion to 20° dorsiflexion at 5 deg s(-1) with a dynamometer, and the ankle angle and torque were recorded. After normalizing the data (the initial points of angle and torque were set to zero), we calculated the peak torque and energy. Furthermore, angle-torque data (before and after normalization) were fitted with a second- and fourth-order polynomial, and exponential (Sten-Knudsen) models, and stiffness indices (SISOP, SIFOP, SISK) and AngleSLACK (the angle at which plantar-flexor passive torque equals zero) were calculated. The stretch reflex gain and offset were determined from 0-10° dorsiflexion at 50, 90, 120 and 150 deg s(-1). After logarithmic transformation, Pearson's correlation coefficients were calculated.. MAS, calf circumference, MG thickness, peak torque and SIFOP significantly decreased with injury duration (r log-log=-0.63, -0.69, -0.63, -0.53 and -0.55, respectively, P<0.05). The peak torque and SIFOP maintained significant relationships even after excluding impacts from muscle morphology.. Plantar-flexor elasticity in chronic SCI patients decreased with increased injury duration.

Topics: Adult; Ankle; Cross-Sectional Studies; Female; Humans; Lower Extremity; Male; Middle Aged; Muscle Spasticity; Muscle, Skeletal; Spinal Cord Injuries; Time Factors; Torque; Young Adult

Shoulder joint pain is a frequent secondary complaint for people following spinal cord injury (SCI).. The purpose of this study was to determine predictors of shoulder joint pain in people with paraplegia.. A 3-year longitudinal study was conducted. Participants were people with paraplegia who used a manual wheelchair for at least 50% of their mobility and were asymptomatic for shoulder pain at study entry. Participants were classified as having developed shoulder pain if they experienced an increase of ≥10 points on the Wheelchair User's Shoulder Pain Index in the 3-year follow-up period. Measurements of maximal isometric shoulder torques were collected at study entry (baseline), 18 months, and 3 years. Daily activity was measured using a wheelchair odometer, and self-reported daily transfer and raise frequency data were collected by telephone every 6 weeks.. Two hundred twenty-three participants were enrolled in the study; 39.8% developed shoulder pain over the 3-year follow-up period. Demographic variables and higher activity levels were not associated with shoulder pain onset. Baseline maximal isometric torque (normalized by body weight) in all shoulder muscle groups was 10% to 15% lower in participants who developed shoulder pain compared with those who remained pain-free. Lower shoulder adduction torque was a significant predictor of shoulder pain development (log-likelihood test=11.38), but the model explained only 7.5% of shoulder pain onset and consequently is of limited clinical utility.. Time since SCI varied widely among participants, and transfer and raise activity was measured by participant recall.. Participants who developed shoulder pain had decreased muscle strength, particularly in the shoulder adductors, and lower levels of physical activity prior to the onset of shoulder pain. Neither factor was a strong predictor of shoulder pain onset.

Topics: Adult; Cohort Studies; Female; Humans; Male; Motor Activity; Muscle Strength; Muscle, Skeletal; Paraplegia; Risk Factors; Shoulder Pain; Spinal Cord Injuries; Torque; Weight-Bearing; Wheelchairs

A vertical slope of sidewalks significantly inhibits to the mobility of manual wheelchair users in their daily life. International guidelines of the vertical slope are specified approximately 4% or 5% (1:20) gradient or less as preferred, and allow 8.3% (1:12) as its maximum when it is impossible. Relevant research of the physical strain for wheelchair users with pushing on slopes, and the validity assessment of slope guidelines have been investigated. However, the analysis for the effect of a slope distance and their transient performance are still remained. The purpose of this study is to clarify the physiological and biomechanical characteristics of manual wheelchair users that propelling a wheelchair on an uphill slope. We measured these data by a metabolic analysis system, a heart rate monitor system and an instrumented wheelchair wheel. Sixteen unimpaired subjects (non-wheelchair users) were examined to investigate the effect of a long slope with 120m distance and 8% gradient. And five wheelchair users with cervical cord injury were examined to evaluate the influence of different gradients (5%, 6.7%, 8.3%, 10% and 12.5%) with 3m length in laboratory. Our experimental results of the long slope showed that wheelchair propulsion velocity and power increased considerably at the beginning of the slope where the peak mean value of them were 0.96 m/s and 70.8W and they decreased linearly to 0.55m/s and 33.6W at final interval. A mean oxygen uptake and heart rate were increased as the distance increased and their results indicated the extremely high exercise intensity at a final interval that were 1.2liter /min and 152bpm. While wheelchair pushing cadence reduced after an initial interval, mean of strokes per10m increased to compensate the decrease of upper limb's power. The results of different gradients indicated that the normalized power of subjects with cervical cord injury was significant difference between each subject in the ability to climb a slope. Mean normalized power were 0.23W/kg on a 5% slope, 0.24W/kg on 6.7%, and 0.26W/kg on 8.3% respectively. Based on these findings, we examined the relationship between the theoretical normalized power and the lowest velocity to climb a slope, and we might indicate the ability to push on an uphill slope for the persons with manual wheelchair user.

Topics: Acceleration; Activities of Daily Living; Adolescent; Adult; Biomechanical Phenomena; Energy Metabolism; Humans; Male; Psychomotor Performance; Risk Factors; Spinal Cord Injuries; Task Performance and Analysis; Torque; Wheelchairs

Lower extremity strength has been reported to relate to walking ability, however, the relationship between voluntary lower extremity muscle function as measured by isokinetic dynamometry and walking have not been thoroughly examined in individuals with incomplete spinal cord injury (iSCI).. To determine the extent to which measures of maximal voluntary isometric contraction (MVIC) and rate of torque development (RTD) in the knee extensor (KE) and plantar flexor (PF) muscle groups correlate with self-selected overground walking speed and spatiotemporal characteristics of walking.. Twenty-two subjects with chronic (>6 months) iSCI participated in a cross-sectional study. Values for MVIC and RTD in the KE and PF muscle groups were determined by isokinetic dynamometry. Walking speed and spatiotemporal characteristics of walking were measured during overground walking.. MVIC in the KE and PF muscle groups correlated significantly with walking speed. RTD was significantly correlated with walking speed in both muscle groups, the more-involved PF muscle group showing the strongest correlation with walking speed (r = 0.728). RTD in the KE and PF muscle groups of the more-involved limb was significantly correlated with single support time of the more-involved limb.. These data demonstrate that lower extremity strength is associated with walking ability after iSCI. Correlations for the muscle groups of the move-involved side were stronger compared to the less-involved limb. In addition, PF function is highlighted as a potential limiting factor to walking speed along with the importance of RTD.

Topics: Adolescent; Adult; Cross-Sectional Studies; Female; Humans; Isometric Contraction; Leg; Male; Middle Aged; Muscle Strength Dynamometer; Spinal Cord Injuries; Torque; Walking; Young Adult

Spinal cord injury (SCI) is characterized by rapid bone loss and an increased risk of fragility fracture around regions of the knee. Our purpose was to quantify changes in torsional stiffness K and strength Tult at the proximal tibia due to actual bone loss and simulated bone recovery in acute SCI.. Computed tomography scans were acquired on ten subjects with acute SCI at serial time points separated by a mean of 3.9months (range 3.0 to 4.8months). Reductions in bone mineral were quantified and a validated subject-specific finite element modeling procedure was used to predict changes in K and Tult. The modeling procedure was subsequently used to examine the effect of simulated hypothetical treatments, in which bone mineral of the proximal tibiae were restored to baseline levels, while all other parameters were held constant.. During the acute period of SCI, subjects lost 8.3±4.9% (p<0.001) of their bone mineral density (BMD). Reductions in K (-9.9±6.5%; p=0.002) were similar in magnitude to reductions in BMD, however reductions in Tult (-15.8±13.8%; p=0.005) were some 2 times greater than the reductions in BMD. Owing to structural changes in geometry and mineral distribution, Tult was not necessarily recovered when bone mineral was restored to baseline, but was dependent upon the degree of bone loss prior to hypothetical treatments (r≥0.719; p≤0.019).. Therapeutic interventions to halt or attenuate bone loss associated with SCI should be implemented soon after injury in an attempt to preserve mechanical integrity and prevent fracture.

Topics: Biomechanical Phenomena; Bone Resorption; Female; Finite Element Analysis; Humans; Male; Spinal Cord Injuries; Tomography, X-Ray Computed; Torque

Strength changes in lower limb muscles following robot assisted gait training (RAGT) in subjects with incomplete spinal cord injury (ISCI) has not been quantified using objective outcome measures.. To record changes in the force generating capacity of lower limb muscles (recorded as peak voluntary isometric torque at the knee and hip), before, during and after RAGT in both acute and subacute/chronic ISCI subjects using a repeated measures study design.. Eighteen subjects with ISCI participated in this study (Age range: 26-63 years mean age = 49.3 ± 11 years). Each subject participated in the study for a total period of eight weeks, including 6 weeks of RAGT using the Lokomat system (Hocoma AG, Switzerland). Peak torques were recorded in hip flexors, extensors, knee flexors and extensors using torque sensors that are incorporated within the Lokomat.. All the tested lower limb muscle groups showed statistically significant (p < 0.001) increases in peak torques in the acute subjects. Comparison between the change in peak torque generated by a muscle and its motor score over time showed a non-linear relationship.. The peak torque recorded during isometric contractions provided an objective outcome measure to record changes in muscle strength following RAGT.

Topics: Adult; Exercise Therapy; Female; Gait; Hip Joint; Humans; Isometric Contraction; Knee Joint; Leg; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Outcome Assessment, Health Care; Robotics; Spinal Cord Injuries; Torque

The purpose of this study was to propose a method that allows extraction of the current muscle state under electrically induced fatigue.. The triceps surae muscle of 5 subjects paralyzed by spinal cord injury was fatigued by intermittent electrical stimulation (5 × 5 trains at 30 Hz). Classical fatigue indices representing muscle contractile properties [peak twitch (Pt) and half-relaxation time (HRT)] were assessed before and after each 5-train series and were used to identify 2 relevant parameters (Fm , Ur ) of a previously developed mathematical model using the Sigma-Point Kalman Filter.. Pt declined significantly during the protocol, whereas HRT remained unchanged. Identification of the model parameters with experimental data yielded a model-based fatigue assessment that gave a more stable evaluation of fatigue than classical parameters.. This work reinforces clinical research by providing a tool that clinicians can use to monitor fatigue development during stimulation.

Topics: Adult; Analysis of Variance; Electric Stimulation; Evoked Potentials, Motor; Humans; Middle Aged; Models, Biological; Muscle Contraction; Muscle Fatigue; Online Systems; Paresis; Spinal Cord Injuries; Torque

No comprehensive biomechanical study has documented upper extremity (U/E) kinematics and kinetics during the performance of wheelchair wheelies among manual wheelchair users (MWUs). The aim of this study was to describe movement strategies (kinematics), mechanical loads (kinetics), and power at the nondominant U/E joints during a wheelie among MWUs with spinal cord injury (SCI). During a laboratory assessment, 16 MWUs with SCI completed four wheelie trials on a rigid surface. Each participant's wheelchair was equipped with instrumented wheels to record handrim kinetics, while U/E and wheelchair kinematics were recorded with a 3D motion analysis system. The greatest mean and peak total net joint moments were generated by the shoulder flexors (mean = 7.2 ± 3.5 N·m; peak = 20.7 ± 12.9 N·m) and internal rotators (mean = 3.8 ± 2.2 N·m; peak = 11.4 ± 10.9 N·m) as well as by the elbow flexors (mean = 5.5 ± 2.5 N·m; peak = 14.1 ± 7.6 N·m) during the performance of wheelies. Shoulder flexor and internal rotator efforts predominantly generate the effort needed to lift the front wheels of the wheelchair, whereas the elbow flexor muscles control these shoulder efforts to reach a state of balance. In combination with a task-specific training program that remains essential to properly learn how to control wheelies among MWUs with SCI, rehabilitation professionals should also propose a shoulder flexor, internal rotator, and elbow flexor strengthening program.

Topics: Adult; Arm; Elbow Joint; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Paraplegia; Physical Exertion; Range of Motion, Articular; Shoulder Joint; Spinal Cord Injuries; Task Performance and Analysis; Torque; Wheelchairs

Neuromuscular electrical stimulation (NMES) over a muscle belly (mNMES) generates contractions predominantly through M-waves, while NMES over a nerve trunk (nNMES) can generate contractions through H-reflexes in people who are neurologically intact. We tested whether the differences between mNMES and nNMES are present in people with chronic motor-complete spinal cord injury and, if so, whether they influence contraction fatigue.. Plantar-flexion torque and soleus electromyography were recorded from 8 participants. Fatigue protocols were delivered using mNMES and nNMES on separate days.. nNMES generated contractions that fatigued less than mNMES. Torque decreased the least when nNMES generated contractions, at least partly through H-reflexes (n = 4 participants; 39% decrease), and torque decreased the most when contractions were generated through M-waves, regardless of NMES site (nNMES 71% decrease, n = 4; mNMES, 73% decrease, n = 8).. nNMES generates contractions that fatigue less than mNMES, but only when H-reflexes contribute to the evoked contractions.

Topics: Adult; Analysis of Variance; Electric Stimulation; Electromyography; Evoked Potentials, Motor; Fatigue; H-Reflex; Humans; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Recruitment, Neurophysiological; Spinal Cord Injuries; Torque

The purpose of the current study was to determine the effects of three different pulse durations (200, 350, and 500 microseconds [P200, P350, and P500, respectively]) on oxygen uptake (VO2), cycling performance, and energy expenditure (EE) percentage of fatigue of the knee extensor muscle group immediately and 48 to 72 h after cycling in persons with spinal cord injury (SCI). A convenience sample of 10 individuals with motor complete SCI participated in a repeated-measures design using a functional electrical stimulation (FES) cycle ergometer over a 3 wk period. There was no difference among the three FES protocols on relative VO2 or cycling EE. Delta EE between exercise and rest was 42% greater in both P500 and P350 compared with P200 (p = 0.07), whereas recovery VO2 was 23% greater in P350 compared with P200 (p = 0.03). There was no difference in the outcomes of the three pulse durations on muscle fatigue. Knee extensor torque significantly decreased immediately after (p < 0.001) and 48 to 72 h after (p < 0.001) FES leg cycling. Lengthening pulse duration did not affect submaximal or relative VO2 or EE, total EE, and time to fatigue. Greater recovery VO2 and delta EE were noted in P350 and P500 compared with P200. An acute bout of FES leg cycling resulted in torque reduction that did not fully recover 48 to 72 h after cycling.

Topics: Adult; Bicycling; Electric Stimulation Therapy; Energy Metabolism; Exercise Test; Exercise Therapy; Exercise Tolerance; Female; Humans; Male; Middle Aged; Muscle Fatigue; Muscle, Skeletal; Oxygen Consumption; Spinal Cord Injuries; Time Factors; Torque

Cervical spinal cord injury and acquired brain injury commonly imply a reduction in the upper extremity function which complicates, or even constrains, the performance of basic activities of daily living. Neurological rehabilitation in specialised hospitals is a common treatment for patients with neurological disorders. This study presents a practical methodology for the objective and quantitative evaluation of the upper extremity motion during an activity of daily living of those subjects. A new biomechanical model (with 10 rigid segments and 20 degrees of freedom) was defined to carry out kinematic, dynamic and energetic analyses of the upper extremity motion during a reaching task through data acquired by an optoelectronic system. In contrast to previous upper extremity models, the present model includes the analysis of the grasp motion, which is considered as crucial by clinicians. In addition to the model, we describe a processing and analysis methodology designed to present relevant summaries of biomechanical information to rehabilitation specialists. As an application case, the method was tested on a total of four subjects: three healthy subjects and one pathological subject suffering from cervical spinal cord injury. The dedicated kinematic, dynamic and energetic analyses for this particular case are presented. The resulting set of biomechanical measurements provides valuable information for clinicians to achieve a thorough understanding of the upper extremity motion, and allows comparing the motion of healthy and pathological cases.

Topics: Biomechanical Phenomena; Female; Hand Strength; Humans; Male; Models, Biological; Motion; Movement; Muscle, Skeletal; Range of Motion, Articular; Spinal Cord Injuries; Torque; Upper Extremity

Electrical stimulation over a motor nerve yields muscle force via a combination of direct and reflex-mediated activation. We determined the influence of fatigue on reflex-mediated responses induced during supra-maximal electrical stimulation in humans with complete paralysis.. We analyzed soleus electromyographic (EMG) activity during repetitive stimulation (15 Hz, 125 contractions) in 22 individuals with complete paralysis. The bout of stimulation caused significant soleus muscle fatigue (53.1% torque decline).. Before fatigue, EMG at all latencies after the M-wave was less than 1% of the maximal M-wave amplitude (% MaxM). After fatigue there was a fourfold (p < 0.05) increase in EMG at the H-reflex latency; however, the overall magnitude remained low (< 2% change in % MaxM). There was no increase in "asynchronous" EMG ∼ 1 s after the stimulus train.. Fatigue enhanced the activation to the paralyzed soleus muscle, but primarily at the H-reflex latency. The overall influence of this reflex modulation was small. Soleus EMG was not elevated during fatigue at latencies consistent with asynchronous activation.. These findings support synchronous reflex responses increase while random asynchronous reflex activation does not change during repetitive supra-maximal stimulation, offering a clinical strategy to consistently dose stress to paralyzed tissues.

Topics: Adult; Aged; Electric Stimulation; Electric Stimulation Therapy; Electromyography; Female; H-Reflex; Humans; Male; Middle Aged; Muscle Fatigue; Muscle, Skeletal; Paralysis; Reaction Time; Reflex; Spinal Cord Injuries; Torque; Young Adult

The mechanisms underlying poor glucose tolerance in persons with spinal cord injury (SCI), along with its improvement after several weeks of neuromuscular electrical stimulation-induced resistance exercise (NMES-RE) training, remain unclear, but presumably involve the affected skeletal musculature. We, therefore, investigated skeletal muscle signaling pathways associated with glucose transporter 4 (GLUT-4) translocation at rest and shortly after a single bout of NMES-RE in SCI (n = 12) vs. able-bodied (AB, n = 12) men. Subjects completed an oral glucose tolerance test during visit 1 and ≈90 NMES-RE isometric contractions of the quadriceps during visit 2. Muscle biopsies were collected before, and 10 and 60 min after, NMES-RE. We assessed transcript levels of GLUT-4 by quantitative PCR and protein levels of GLUT-4 and phosphorylated- and total AMP-activated protein kinase (AMPK)-α, CaMKII, Akt, and AS160 by immunoblotting. Impaired glucose tolerance in SCI was confirmed by higher (P < 0.05) plasma glucose concentrations than AB at all time points after glucose ingestion, despite equivalent insulin responses to the glucose load. GLUT-4 protein content was lower (P < 0.05) in SCI vs. AB at baseline. Main group effects revealed higher phosphorylation in SCI of AMPK-α, CaMKII, and Akt (P < 0.05), and Akt phosphorylation increased robustly (P < 0.05) following NMES-RE in SCI only. In SCI, low skeletal muscle GLUT-4 protein concentration may, in part, explain poor glucose tolerance, whereas heightened phosphorylation of relevant signaling proteins (AMPK-α, CaMKII) suggests a compensatory effort. Finally, it is encouraging to find (based on Akt) that SCI muscle remains both sensitive and responsive to mechanical loading (NMES-RE) even ≈22 yr after injury.

Topics: Adult; AMP-Activated Protein Kinases; Blood Glucose; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Electric Stimulation Therapy; Glucose; Glucose Intolerance; Glucose Tolerance Test; Glucose Transporter Type 4; Humans; Insulin; Male; Middle Aged; Muscle Contraction; Phosphorylation; Proto-Oncogene Proteins c-akt; Quadriceps Muscle; Resistance Training; Rest; Signal Transduction; Spinal Cord; Spinal Cord Injuries; Torque; Young Adult

Joint contractures are a common complication of many neurologic conditions, and stretching often is advocated to prevent and treat these contractures. However, the magnitude and duration of the stretching done in practice usually are guided by subjective clinical impressions.. Using an established T8 spinal cord injury rat model of knee contracture, we sought to determine what combination of static or intermittent stretching, varied by magnitude (high or low) and duration (long or short), leads to the best (1) improvement in the limitation in ROM; (2) restoration of the muscular and articular factors leading to contractures; and (3) prevention and treatment of contracture-associated histologic alterations of joint capsule and articular cartilage.. Using a rat animal model, the spinal cord was transected completely at the level of T8. The rats were randomly assigned to seven treatment groups (n = 4 per group), which were composed of static or intermittent stretching in combination with different amounts of applied torque magnitude and duration. We assessed the effect of stretching by measuring the ROM and evaluating the histologic alteration of the capsule and cartilage.. Contractures improved in all treated groups except for the low-torque and short-duration static stretching conditions. High-torque stretching was effective against shortening of the synovial membrane and adhesions in the posterosuperior regions. Collagen Type II and VEGF in the cartilage were increased by stretching.. High-torque and long-duration static stretching led to greater restoration of ROM than the other torque and duration treatment groups. Stretching was more effective in improving articular components of contractures compared with the muscular components. Stretching in this rat model prevented shortening and adhesion of the joint capsule, and affected biochemical composition, but did not change morphologic features of the cartilage.. This animal study tends to support the ideas that static stretching can influence joint ROM and histologic qualities of joint tissues, and that the way stretching is performed influences its efficacy. However, further studies are warranted to determine if our findings are clinically applicable.

Topics: Animals; Biomechanical Phenomena; Cartilage, Articular; Collagen Type II; Contracture; Disease Models, Animal; Joint Capsule; Knee Joint; Male; Muscle Stretching Exercises; Range of Motion, Articular; Rats; Rats, Wistar; Spinal Cord Injuries; Time Factors; Torque; Vascular Endothelial Growth Factor A

The purpose of this paper is to propose a new assessment method for evaluating motor function of the patients who are suffering from physical weakness after stroke, incomplete spinal cord injury (iSCI) or other diseases. In this work, we use a robotic device to obtain the information of interaction occur between patient and robot, and use it as a measure for assessing the patients. The Intentional Movement Performance Ability (IMPA) is defined by the root mean square of the interactive torque, while the subject performs given periodic movement with the robot. IMPA is proposed to quantitatively determine the level of subject's impaired motor function. The method is indirectly tested by asking the healthy subjects to lift a barbell to disturb their motor function. The experimental result shows that the IMPA has a potential for providing a proper information of the subject's motor function level.

Topics: Adult; Exercise Therapy; Humans; Male; Man-Machine Systems; Motor Activity; Robotics; Spinal Cord Injuries; Stroke Rehabilitation; Task Performance and Analysis; Torque

Spasticity is a common complication with neurological diseases and CNS lesions. Instrumented systems to evaluate spasticity often cannot provide an immediate result, thus limiting their clinical usefulness. In this study we investigated the accuracy and reliability of the portable Neurokinetics RA1 Ridgidity Analyzer to measure stiffness of the ankle joint in 46 controls, 14 spinal cord injured (SCI) and 23 multiple sclerosis (MS) participants.. Ankle stiffness measures were made twice by two raters, at speeds above and below the expected stretch reflex threshold. Ankle torque was measured with the portable device and a stationary torque motor. Inter- and intra-rater reliability was assessed with the intra-class correlation coefficient (ICC).. Stiffness measures with the portable and stationary devices were significantly correlated for controls and MS participants (p < 0.01). Intra-rater reliability for the portable device ranged from 0.60-0.89 (SCI) and 0.63-0.67 (control) and inter-rater reliability ranged from 0.70-0.73 (SCI) and 0.61-0.77 (control). Ankle stiffness measures in SCI and MS participants were significantly larger than in controls for both slow (p < 0.05) and fast movements (p < 0.01), with stiffness being larger for fast compared to slow movements in SCI and MS participants (p < 0.05), but not in controls (p = 0.5).. The portable device correlated well with measures obtained by a torque motor in both controls and MS participants, showed high intra- and inter-rater reliability for the SCI participants, and could easily distinguish between stiff and control ankle joints. However, the device, in its current form, may be less accurate during rapid movements when inertia contributes to stiffness and the shape of the air-filled pads did not provide a good interface with the foot.. This study demonstrates that a portable device can potentially be a useful diagnostic tool to obtain reliable information of stiffness for the ankle joint.

Topics: Adult; Aged; Ankle Joint; Biomechanical Phenomena; Elasticity; Equipment and Supplies; Female; Humans; Male; Middle Aged; Monitoring, Ambulatory; Movement; Multiple Sclerosis; Muscle Spasticity; Muscle, Skeletal; Observer Variation; Reproducibility of Results; Spinal Cord Injuries; Torque

An understanding of the mechanical effects of botulinum toxin type A (BoNT A) on spastic and voluntary muscle contraction may help predict functional responders.. To compare the effect of BoNT A on the voluntary and stretch reflex-related torques produced by activation of the rectus femoris (RF).. This was a prospective open study where 15 incomplete spinal cord injury patients, impaired by a stiff-knee gait, with RF hyperactivity in mid-swing quantified by formal gait analysis (GA), were assessed before and after RF BoNT A injection (Botox, 200 UI).. Included isokinetic peak torque (and angle at peak torque) at 0° (supine) and 90° (seated) during passive stretch (10 deg/s, 90 deg/s, and 150 deg/s), and voluntary contraction (60 deg/s) of the quadriceps. Secondary measures included impairment by Modified Tardieu Scale (MTS), peak knee flexion and spatial-temporal data by GA, activity (6-minute walking test, timed stair climbing), and discomfort (Verbal Rating Scale).. Voluntary torque decreased (-16%; P = .0004) but with only a trend toward a decrease in stretch reflex-related torque. The angle at spastic torque increased at 90 deg/s (+5°; P = .03), whereas MTS, peak knee flexion (+4°; P = .01), spatial-temporal data, timed stair climbing test (25%; P = .02), and discomfort were significantly improved.. BoNT A appeared to delay the stretch-reflex angle at peak torque, whereas the voluntary torque decreased. After strict patient selection, BoNT A injection into the RF muscle led to improvements in impairment, activity, and discomfort.

Topics: Adult; Botulinum Toxins, Type A; Electromyography; Female; Gait Disorders, Neurologic; Humans; Male; Middle Aged; Muscle Strength Dynamometer; Muscle, Skeletal; Neuromuscular Agents; Pilot Projects; Prospective Studies; Range of Motion, Articular; Reflex, Stretch; Severity of Illness Index; Spinal Cord Injuries; Torque; Treatment Outcome

To evaluate the effect of backrest height on wheelchair propulsion kinematics and kinetics.. An intervention study with repeated measures.. University laboratory.. Convenience sample included manual wheelchair users (N=36; 26 men and 10 women) with spinal cord injuries ranging from T8 to L2.. Participants propelled on a motor-driven treadmill for 2 conditions (level and slope of 3°) at a constant speed of 0.9 m/s while using in turn a sling backrest fixed at 40.6 cm (16 in) high (high backrest) and a lower height set at 50% trunk length (low backrest).. Cadence, stroke angle, peak shoulder extension angle, shoulder flexion/extension range of motion, and mechanical effective force.. Pushing with the low backrest height enabled greater range of shoulder motion (P<.01), increased stroke angle (P<.01), push time (P<.01), and reduced cadence (P=.01) regardless of whether the treadmill was level or sloped.. A lower cadence can be achieved when pushing with a lower backrest, which decreases the risk of developing upper-limb overuse related injuries. However, postural support, comfort, and other activities of daily living must also be considered when selecting a backrest height for active, long-term wheelchair users. The improvements found when using the low backrest were found regardless of slope type. Pushing uphill demanded significantly higher resultant and tangential force, torque, mechanical effective force, and cadence.

Topics: Acceleration; Adaptation, Physiological; Adult; Aged; Biomechanical Phenomena; Equipment Design; Female; Humans; Male; Middle Aged; Psychomotor Performance; Range of Motion, Articular; Spinal Cord Injuries; Torque; Upper Extremity; Wheelchairs

The principal aim of our study was the determination of the effectiveness of a standardized ratio, allometric scaling model and a gamma function model in normalizing the isometric torque data of spinal cord patients and healthy subjects. For this purpose we studied a sample of 21 healthy males and 23 spinal cord injury males. The experiment consisted of the measurement of the force of the upper limb movement executed by all the subjects. We also determined anthropometric variables with dual-energy x-ray absorptiometry. The experimental data were analyzed with 3 force normalization methods. Our results indicate that the most important confounding variable was the fat free mass of the dominant upper limb (r>0.36, p<0.05). With the standardization by body mass and allometric scaling model, the normalized torque was influenced by body size variables. However, the normalized torque by the gamma function model was independent of body size measures. Paraplegics were weaker (p<0.05) in extension movements when the data were normalized by the gamma function model. In summary, this study shows that the gamma function model with fat free mass of the dominant upper limb was more effective than the standardized ratio in removing the influence of body size variables.

Topics: Absorptiometry, Photon; Adult; Anthropometry; Body Composition; Body Size; Humans; Male; Models, Biological; Muscle Strength; Muscle, Skeletal; Paraplegia; Spinal Cord Injuries; Torque; Upper Extremity

Prospective cohort study.. To determine incidence of contracture and develop prediction models to identify patients susceptible to contracture after spinal cord injury.. Two Sydney spinal cord injury units.. A total of 92 consecutive patients with acute spinal cord injury were assessed within 35 days of injury and 1 year later. Incidence of contracture at 1 year was measured in all major appendicular joints by categorizing range of motion on a 4-point scale (0-no contracture to 3-severe contracture), and in the wrist, elbow, hip and ankle by measuring range of motion at standardized torque. Multivariate models were developed to predict contracture at 1 year using age, neurological status, spasticity, pain and limb fracture recorded at the time of injury.. At 1 year, 66% of participants developed at least one contracture (defined as ≥1 point deterioration on the 4-point scale). Incidence of contracture at each joint was: shoulder 43%, elbow and forearm 33%, wrist and hand 41%, hip 32%, knee 11% and ankle 40%. Incidence of contracture determined by standardized torque measures of range (defined as loss of ≥10 degrees) was: elbow 27%, wrist 26%, hip 23% and ankle 25%. Prediction models were statistically significant but lacked sufficient predictive accuracy to be clinically useful (R(2)≤31%).. The incidence of contracture in major joints 1 year after spinal cord injury ranges from 11-43%. The ankle, wrist and shoulder are most commonly affected. It is difficult to accurately predict those susceptible to contracture soon after injury.

Topics: Adult; Cohort Studies; Contracture; Humans; Incidence; Joints; Middle Aged; Muscle Spasticity; Predictive Value of Tests; Prospective Studies; Range of Motion, Articular; Severity of Illness Index; Spinal Cord Injuries; Torque

Spasticity is a common disorder following spinal cord injury that can impair function and quality of life. While a number of mechanisms are thought to play a role in spasticity, the role of motoneuron persistent inward currents (PICs) is emerging as pivotal. The presence of PICs can be evidenced by temporal summation or wind-up of reflex responses to brief afferent inputs. In this study, a combined neurophysiological and novel biomechanical approach was used to assess the effects of passive exercise and modafinil administration on hyper-reflexia and spasticity following complete T-10 transection in the rat. Animals were divided into 3 groups (n=8) and provided daily passive cycling exercise, oral modafinil, or no intervention. After 6weeks, animals were tested for wind-up of the stretch reflex (SR) during repeated dorsiflexion stretches of the ankle. H-reflexes were tested in a subset of animals. Both torque and gastrocnemius electromyography showed evidence of SR wind-up in the transection only group that was significantly different from both treatment groups (p<0.05). H-reflex frequency dependent depression was also restored to normal levels in both treatment groups. The results provide support for the use of passive cycling exercise and modafinil in the treatment of spasticity and provide insight into the possible contribution of PICs.

Topics: Analysis of Variance; Animals; Benzhydryl Compounds; Chronic Disease; Disease Models, Animal; Electromyography; Female; H-Reflex; Modafinil; Muscle Spasticity; Muscle, Skeletal; Neuroprotective Agents; Physical Conditioning, Animal; Random Allocation; Rats; Rats, Sprague-Dawley; Reflex, Stretch; Severity of Illness Index; Spinal Cord Injuries; Time Factors; Torque

Muscle fatigue prevents repetitive use of paralyzed muscle after spinal cord injury (SCI).. This study compared the effects of hybrid patterns of muscle stimulation in individuals with acute and chronic SCI.. Individuals with chronic (n = 11) or acute paralysis (n = 3) underwent soleus muscle activation with a constant (CT) or doublet (DT) stimulation train before and at various times after a fatigue protocol.. The chronically paralyzed soleus was highly fatigable with a fatigue index (FI) of 19% ± 6%, whereas the acutely paralyzed soleus was fatigue resistant (FI = 89% ± 8%). For the chronically paralyzed group, the DT protocol caused less than 5% improvement in peak and mean force relative to the CT protocol before fatigue; however, after fatigue the DT protocol caused an increase in peak and mean force (>10%), compared with the CT protocol (P < .05). As the chronically paralyzed muscle developed low-frequency fatigue, the DT protocol became more effective than the CT protocol (P < .05). The DT protocol increased the rate of torque development before fatigue (42% ± 78%), after fatigue (62% ± 52%), and during recovery (87% ± 54% to 101% ± 56%; P < .05). The acutely paralyzed group showed minimal change in peak and mean torque with the DT protocol.. Chronic reduced activity is associated with muscle adaptations (slow to fast) that render the muscle more amenable to force enhancement through doublet train activation after fatigue. These findings are applicable to patients using neuromuscular stimulation.

Topics: Acute Disease; Adult; Chronic Disease; Electric Stimulation Therapy; Female; Humans; Male; Muscle Fatigue; Muscle, Skeletal; Paralysis; Spinal Cord Injuries; Time Factors; Torque; Young Adult

Despite greater muscle fatigue in individuals with spinal cord injury (SCI) when compared to neurologically intact subjects using neuromuscular electrical stimulation (NMES)protocols, few studies have investigated the extent of volitional fatigue in motor incomplete SCI. Using an established protocol of 20 repeated, intermittent, maximal volitional effort (MVE) contractions, we previously demonstrated that subjects with incomplete SCI unexpectedly demonstrated a 15% increase in peak knee extensor torques within the first five MVEs with minimal evidence of fatigue after 20 contraction. In the present study, we investigated potential segmental mechanisms underlying this supramaximal torque generation. Changes in twitch properties and maximum compound muscle action potentials (M-waves) were assessed prior to and following one, three and five MVEs, revealing a significant 17% increase only in maximum twitch torques after a single MVE. Despite this post-activation potentiation of the muscle, use of conventional NMES protocols to elicit repeated muscular contractions resulted in a significant decrease in evoked torque generation, suggesting limited the muscular contributions to the observed phenomenon. To evaluate potential central mechanisms underlying the augmented torques, non-linear responses to wide-pulse width (1 ms), low-intensity, variable-frequency (25–100 Hz) NMES were also tested prior to and following repeated MVEs.When variable-frequency NMES was applied following the repeated MVEs, augmented and prolonged torques were observed and accompanied by sustained quadriceps electromyographic activity often lasting > 2s after stimulus termination. Such data suggest a potential contribution of elevated spinal excitability to the reserve in volitional force generation in incomplete SCI.

Topics: Action Potentials; Adult; Electric Stimulation; Electromyography; Female; Humans; Male; Middle Aged; Motor Activity; Muscle Contraction; Muscle Fatigue; Quadriceps Muscle; Spinal Cord Injuries; Torque; Young Adult

After spinal cord injury (SCI), alterations in intrinsic motoneuron properties have been shown to be partly responsible for spastic reflex behaviors in human SCI. In particular, a dysregulation of voltage-dependent depolarizing persistent inward currents (PICs) may permit sustained muscle contraction after the removal of a brief excitatory stimulus. Windup, in which the motor response increases with repeated activation, is an indicator of PICs. Although windup of homonymous stretch reflexes has been shown, multijoint muscle activity is often observed following imposed limb movements and may exhibit a similar windup phenomenon. The purpose of this study was to identify and quantify windup of multijoint reflex responses to repeated imposed hip oscillations. Ten chronic SCI subjects participated in this study. A custom-built servomotor apparatus was used to oscillate the legs about the hip joint bilaterally and unilaterally from 10° of extension to 40° flexion for 10 consecutive cycles. Surface electromyograms (EMGs) and joint torques were recorded from both legs. Consistent with a windup response, hip and knee flexion/extension and ankle plantarflexion torque and EMG responses varied according to movement cycle number. The temporal patterns of windup depended on the muscle groups that were activated, which may suggest a difference in the response of neurons in different spinal pathways. Furthermore, because windup was seen in muscles that were not being stretched, these results imply that changes in interneuronal properties are also likely to be associated with windup of spastic reflexes in human SCI.

Topics: Adult; Aged; Ankle Joint; Electromyography; Female; Hip Joint; Humans; Knee Joint; Leg; Male; Middle Aged; Motor Neurons; Muscle Spasticity; Paralysis; Posture; Range of Motion, Articular; Reflex, Abnormal; Spasm; Spinal Cord Injuries; Torque; Young Adult

In patients with complete spinal cord injury, fatigue occurs rapidly and there is no proprioceptive feedback regarding the current muscle condition. Therefore, it is essential to monitor the muscle state and assess the expected muscle response to improve the current FES system toward adaptive force/torque control in the presence of muscle fatigue. Our team implanted neural and epimysial electrodes in a complete paraplegic patient in 1999. We carried out a case study, in the specific case of implanted stimulation, in order to verify the corresponding torque prediction based on stimulus evoked EMG (eEMG) when muscle fatigue is occurring during electrical stimulation. Indeed, in implanted stimulation, the relationship between stimulation parameters and output torques is more stable than external stimulation in which the electrode location strongly affects the quality of the recruitment. Thus, the assumption that changes in the stimulation-torque relationship would be mainly due to muscle fatigue can be made reasonably. The eEMG was proved to be correlated to the generated torque during the continuous stimulation while the frequency of eEMG also decreased during fatigue. The median frequency showed a similar variation trend to the mean absolute value of eEMG. Torque prediction during fatigue-inducing tests was performed based on eEMG in model cross-validation where the model was identified using recruitment test data. The torque prediction, apart from the potentiation period, showed acceptable tracking performances that would enable us to perform adaptive closed-loop control through implanted neural stimulation in the future.

Topics: Electric Stimulation Therapy; Electrodes, Implanted; Electromyography; Evoked Potentials, Motor; Follow-Up Studies; Humans; Muscle Fatigue; Neurons; Predictive Value of Tests; Spinal Cord Injuries; Torque

Robotic locomotor training devices have gained popularity in recent years, yet little has been reported regarding contact forces experienced by the subject performing automated locomotor training, particularly in animal models of neurological injury. The purpose of this study was to develop a means for acquiring contact forces between a robotic device and a rodent model of spinal cord injury through instrumentation of a robotic gait training device (the rat stepper) with miniature force/torque sensors. Sensors were placed at each interface between the robot arm and animal's hindlimb and underneath the stepping surface of both hindpaws (four sensors total). Twenty four female, Sprague-Dawley rats received mid-thoracic spinal cord transections as neonates and were included in the study. Of these 24 animals, training began for 18 animals at 21 days of age and continued for four weeks at five min/day, five days/week. The remaining six animals were untrained. Animal-robot contact forces were acquired for trained animals weekly and untrained animals every two weeks while stepping in the robotic device with both 60 and 90% of their body weight supported (BWS). Animals that received training significantly increased the number of weight supported steps over the four week training period. Analysis of raw contact forces revealed significant increases in forward swing and ground reaction forces during this time, and multiple aspects of animal-robot contact forces were significantly correlated with weight bearing stepping. However, when contact forces were normalized to animal body weight, these increasing trends were no longer present. Comparison of trained and untrained animals revealed significant differences in normalized ground reaction forces (both horizontal and vertical) and normalized forward swing force. Finally, both forward swing and ground reaction forces were significantly reduced at 90% BWS when compared to the 60% condition. These results suggest that measurement of animal-robot contact forces using the instrumented rat stepper can provide a sensitive and reliable measure of hindlimb locomotor strength and control of flexor and extensor muscle activity in neurologically impaired animals. Additionally, these measures may be useful as a means to quantify training intensity or dose-related functional outcomes of automated training.

Topics: Animals; Biomechanical Phenomena; Body Weight; Female; Hindlimb; Locomotion; Mechanical Phenomena; Physical Conditioning, Animal; Rats; Rats, Sprague-Dawley; Robotics; Spinal Cord Injuries; Torque

Investigate shoulder joint kinetics over a range of daily activity and mobility tasks associated with manual wheelchair propulsion to characterize demands placed on the shoulder during the daily activity of manual wheelchair users.. Case series.. Twelve individuals who were experienced manual wheelchair users.. Upper extremity kinematics and handrim wheelchair kinetics were measured over level propulsion, ramp propulsion, start and stop over level terrain, and a weight relief maneuver. Shoulder intersegmental forces and moments were calculated from inverse dynamics for all conditions.. Weight relief resulted in significantly higher forces and ramp propulsion resulted in significantly higher moments than the other conditions. Surprisingly, the start condition resulted in large intersegmental moments about the shoulder equivalent with that of the ramp propulsion, while the demand imparted by the stop condition was shown to be equivalent to level propulsion across all forces and moments.. This study provides characterization of daily living and mobility activities associated with manual wheelchair propulsion not previously reported and identifies activities that result in higher shoulder kinetics when compared to standard level propulsion.

Topics: Adult; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Physical Exertion; Range of Motion, Articular; Shoulder Joint; Spinal Cord Injuries; Torque; Wheelchairs

Inverse dynamic methods have been widely used to estimate joint loads during manual wheelchair propulsion. However, the interpretation of 3D net joint moments and powers is not always straightforward. It has been suggested to use joint coordinate systems (expression of joint moment on anatomical axes) and the 3D angle between joint moment and angular velocity vectors (propulsion, resistance or stabilization joint configuration) for a better understanding of joint dynamics.. Nine spinal cord injured subjects equipped with reflective markers propelled in a wheelchair with an instrumented wheel. Inverse dynamic results were interpreted using joint coordinate systems, 3D joint power and the 3D angle between the joint moment and joint angular velocity vectors at the three upper limb joints. The 3D angle was used to determine if the joints were predominantly driven (angle close to 0 or 180 degrees) or stabilized (angle close to 90 degrees ).. The wrist and elbow joints are mainly in a stabilization configuration (angle close to 90 degrees ) with a combination of extension and ulnar deviation moments and an adduction moment respectively. The shoulder is in a propulsion configuration, but close to stabilization (angle hardly below 60 degrees ) with a combination of flexion and internal rotation moments.. Stabilization configuration at the joints could partly explain the low mechanical efficiency of manual wheelchair propulsion and could give insight about injury risk at the wrist, elbow and shoulder joints.

Topics: Elbow Joint; Female; Humans; Male; Middle Aged; Movement; Physical Exertion; Range of Motion, Articular; Shoulder Joint; Spinal Cord Injuries; Torque; Wheelchairs; Wrist Joint

Using "painless" magnetic stimulation (FMS) to support the cycling of paretic subjects with preserved sensation is possible and potentially superior to electrical stimulation (FES). We investigated the dependence of the torque and the pain evoked by FMS and FES on stimulation conditions in order to optimize magnetic stimulation.. Torque and pain induced by quadriceps stimulation in 13 subjects with paresis and preserved sensation (due to multiple sclerosis) were compared under the conditions: (1) small vs large stimulated surfaces of the thigh, (2) varying contraction velocities of the muscle (isometric vs 15 and 30 rpm isokinetic speed), (3) FMS vs FES modalities, and (4) varying magnetic coil locations.. Torque and pain significantly depended on the amount of surface and location of stimulation during FMS, on the stimulation modality, and on the muscle contraction velocity during FES and FMS. FMS with a saddle-shaped coil produced more torque (p<0.05) than any other stimulation modality, even at 30 rpm velocity.. To support leg cycling of subjects with preserved sensation, the application of FMS stimulation with a large-surface saddle-shaped coil and the focusing of stimulation on the lateral-frontal surface of the thigh produces greater torque and less pain than FES.. Optimized magnetic stimulation is a superior alternative to electrical stimulation in the rehabilitation of subjects with preserved sensation.

Topics: Adult; Disease Progression; Electric Stimulation; Electromyography; Female; Humans; Isometric Contraction; Magnetic Field Therapy; Magnetic Resonance Imaging; Male; Middle Aged; Multiple Sclerosis; Muscle, Skeletal; Pain; Paresis; Spinal Cord Injuries; Thigh; Torque

Despite numerous investigations, the impact of tizanidine, an anti-spastic medication, on changes in reflex and muscle mechanical properties in spasticity remains unclear. This study was designed to help us understand the mechanisms of action of tizanidine on spasticity in spinal cord injured subjects with incomplete injury, by quantifying the effects of a single dose of tizanidine on ankle muscle intrinsic and reflex components.. A series of perturbations was applied to the spastic ankle joint of twenty-one spinal cord injured subjects, and the resulting torques were recorded. A parallel-cascade system identification method was used to separate intrinsic and reflex torques, and to identify the contribution of these components to dynamic ankle stiffness at different ankle positions, while subjects remained relaxed.. Following administration of a single oral dose of Tizanidine, stretch evoked joint torque at the ankle decreased significantly (p < 0.001) The peak-torque was reduced between 15% and 60% among the spinal cord injured subjects, and the average reduction was 25%. Using systems identification techniques, we found that this reduced torque could be attributed largely to a reduced reflex response, without measurable change in the muscle contribution. Reflex stiffness decreased significantly across a range of joint angles (p < 0.001) after using tizanidine. In contrast, there were no significant changes in intrinsic muscle stiffness after the administration of tizanidine.. Our findings demonstrate that tizanidine acts to reduce reflex mechanical responses substantially, without inducing comparable changes in intrinsic muscle properties in individuals with spinal cord injury. Thus, the pre-post difference in joint mechanical properties can be attributed to reflex changes alone. From a practical standpoint, use of a single "test" dose of Tizanidine may help clinicians decide whether the drug can helpful in controlling symptoms in particular subjects.

Topics: Adrenergic alpha-2 Receptor Agonists; Adrenergic alpha-Agonists; Adult; Ankle Joint; Clonidine; Elasticity; Humans; Muscle Spasticity; Muscle, Skeletal; Physical Stimulation; Range of Motion, Articular; Receptors, Adrenergic, alpha-2; Reflex; Spinal Cord Injuries; Torque

Although spasticity has been defined as an increase in velocity-dependent stretch reflexes and muscle hypertonia during passive movement, the measurement of flexor muscle paresis may better characterize the negative impact of this syndrome on residual motor function following incomplete spinal cord injury (iSCI). In this longitudinal study Tibialis Anterior (TA) muscle paresis produced by a loss in maximal voluntary contraction during dorsiflexion and ankle flexor muscle coactivation during ramp-and-hold controlled plantarflexion was measured in ten patients during subacute iSCI. Tibialis Anterior activity was measured at approximately two-week intervals between 3-5 months following iSCI in subjects with or without spasticity, characterized by lower-limb muscle hypertonia and/or involuntary spasms. Following iSCI, maximal voluntary contraction ankle flexor activity was lower than that recorded from healthy subjects, and was further attenuated by the presence of spasticity. Furthermore the initially high percentage value of TA coactivation increased at 75% but not at 25% maximal voluntary torque (MVT), reflected by an increase in TA coactivation gain (75%/25% MVT) from 2.5+/-0.4 to 7.5+/-1.9, well above the control level of 2.9+/-0.2. In contrast contraction-dependent TA coactivation gain decreased from 2.4+/-0.3 to 1.4+/-0.1 during spasticity. In conclusion the adaptive increase in TA coactivation gain observed in this pilot study during subacute iSCI was also sensitive to the presence of spasticity. The successful early diagnosis and treatment of spasticity would be expected to further preserve and promote adaptive motor function during subacute iSCI neurorehabilitation.

Topics: Adult; Aged; Ankle; Ankle Joint; Electromyography; Humans; Longitudinal Studies; Male; Middle Aged; Movement; Muscle Contraction; Muscle Spasticity; Muscle Tonus; Muscle, Skeletal; Pilot Projects; Recovery of Function; Spinal Cord Injuries; Torque; Young Adult

The purpose of this study was to examine the reflex effects of electrical stimulation applied to the thigh using skin electrodes, targeting the sensory fibers of the rectus femoris and sartorius, in people with spinal cord injury (SCI). Thirteen individuals with SCI were recruited to participate in experiments using prolonged electrical stimuli on the right medial thigh over the regions of the sartorius and rectus femoris muscles. Three stimuli, spaced 20 s apart, were applied at 30 Hz for 1 s at four different intensities (15-60 mA) while subjects rested in a seated position. Isometric joint torques of the hip, knee and ankle, and electromyograms (EMGs) from six muscles of the leg were recorded during the stimulation. Early in the stimulation, a flexion response was observed at the hip and ankle, analogous to a flexor reflex; however, this response was usually followed by a "rebound" response consisting of hip extension, knee flexion and ankle plantarflexion, occurring in 10/13 subjects. Stimuli applied in a more lateral (mid thigh) electrode position (i.e. over the rectus femoris) were less effective in producing the response than medial placement, despite vigorous quadriceps activation. This complex reflex response is consistent with activation of a coordinating spinal circuit that could play a role in motor function. The reversal of the reflex pattern emphasizes the potential connection between skin/muscle afferents of the thigh, possibly including sartorius muscle afferents and locomotor reflex centers. This knowledge may be helpful in identifying rehabilitation strategies for enhancing gait training in human SCI.

Topics: Adult; Analysis of Variance; Ankle Joint; Electric Stimulation; Electromyography; Hip Joint; Humans; Knee Joint; Lower Extremity; Middle Aged; Muscle Contraction; Muscle, Skeletal; Quadriceps Muscle; Reflex; Spinal Cord Injuries; Torque; Young Adult

The purpose of this research was to examine the role of isolated ankle-foot load in regulating locomotor patterns in humans with and without spinal cord injury (SCI). We used a powered ankle-foot orthosis to unilaterally load the ankle and foot during robotically assisted airstepping. The load perturbation consisted of an applied dorsiflexion torque designed to stimulate physiological load sensors originating from the ankle plantar flexor muscles and pressure receptors on the sole of the foot. We hypothesized that 1) the response to load would be phase specific with enhanced ipsilateral extensor muscle activity and joint torque occurring when unilateral ankle-foot load was provided during the stance phase of walking and 2) that the phasing of subject produced hip moments would be modulated by varying the timing of the applied ankle-foot load within the gait cycle. As expected, both SCI and nondisabled subjects demonstrated a significant increase (P < 0.05) in peak hip extension moments (142 and 43% increase, respectively) when given ankle-foot load during the stance phase compared with no ankle-foot load. In SCI subjects, this enhanced hip extension response was accompanied by significant increases (P < 0.05) in stance phase gluteus maximus activity (27% increase). In addition, when ankle-foot load was applied either 200 ms earlier or later within the gait cycle, SCI subjects demonstrated significant phase shifts ( approximately 100 ms) in hip moment profile (P < 0.05; i.e., the onset of hip extension moments occurred earlier when ankle-foot load was applied earlier). This study provides new insights into how individuals with spinal cord injury use sensory feedback from ankle-foot load afferents to regulate hip joint moments and muscle activity during gait.

Topics: Adult; Analysis of Variance; Ankle; Ankle Joint; Biomechanical Phenomena; Case-Control Studies; Electromyography; Female; Functional Laterality; Gait Disorders, Neurologic; Hip; Humans; Locomotion; Male; Movement; Muscle, Skeletal; Orthotic Devices; Posture; Range of Motion, Articular; Spinal Cord Injuries; Torque; Weight-Bearing; Young Adult

Neuromuscular electrical stimulation (NMES) can be used to activate paralyzed or paretic muscles to generate functional or therapeutic movements. The goal of this research was to develop a rodent model of NMES-assisted movement therapy after spinal cord injury (SCI) that will enable investigation of mechanisms of NMES-induced plasticity, from the molecular to systems level. Development of the model requires accurate mapping of electrode and muscle stimulation sites, the capability to selectively activate muscles to produce graded contractions of sufficient strength, stable anchoring of the implanted electrode within the muscles and stable performance with functional reliability over several weeks of the therapy window. Custom designed electrodes were implanted chronically in hindlimb muscles of spinal cord transected rats. Mechanical and electrical stability of electrodes and the ability to achieve appropriate muscle recruitment and joint angle excursion were assessed by characterizing the strength duration curves, isometric torque recruitment curves and kinematics of joint angle excursion over 6-8 weeks post implantation. Results indicate that the custom designed electrodes and implantation techniques provided sufficient anchoring and produced stable and reliable recruitment of muscles both in the absence of daily NMES (for 8 weeks) as well as with daily NMES that is initiated 3 weeks post implantation (for 6 weeks). The completed work establishes a rodent model that can be used to investigate mechanisms of neuroplasticity that underlie NMES-based movement therapy after spinal cord injury and to optimize the timing of its delivery.

Topics: Animals; Ankle Joint; Biomechanical Phenomena; Biophysics; Disease Models, Animal; Electric Stimulation; Electrodes, Implanted; Female; Isometric Contraction; Muscle Strength; Muscle, Skeletal; Musculoskeletal Physiological Phenomena; Paraplegia; Rats; Rats, Long-Evans; Spinal Cord Injuries; Time Factors; Torque

To determine whether 9 weeks of locomotor training (LT) results in changes in muscle strength and alterations in muscle size and activation after chronic incomplete spinal cord injury (SCI).. Longitudinal prospective case series.. Five individuals with chronic incomplete SCI completed 9 weeks of LT. Peak isometric torque, torque developed within the initial 200 milliseconds of contraction (Torque 200), average rate of torque development (ARTD), and voluntary activation deficits were determined using isokinetic dynamometry for the knee-extensor (KE) and plantar-flexor (PF) muscle groups before and after LT. Maximum muscle cross-sectional area (CSA) was measured prior to and after LT.. Locomotor training resulted in improved peak torque production in all participants, with the largest increases in the more-involved PF (43.9% +/- 20.0%), followed by the more-involved KE (21.1% +/- 12.3%). Even larger improvements were realized in Torque 200 and ARTD (indices of explosive torque), after LT. In particular, the largest improvements were realized in the Torque 200 measures of the PF muscle group. Improvements in torque production were associated with enhanced voluntary activation in both the KE and ankle PF muscles and an increase in the maximal CSA of the ankle PF muscles.. Nine weeks of LT resulted in positive alterations in the KE and PF muscle groups that included an increase in muscle size, improved voluntary activation, and an improved ability to generate both peak and explosive torque about the knee and ankle joints.

Topics: Adult; Female; Humans; Leg; Longitudinal Studies; Male; Middle Aged; Motor Activity; Muscle Contraction; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Paralysis; Physical Therapy Modalities; Prospective Studies; Recovery of Function; Spinal Cord Injuries; Teaching; Torque; Volition

To examine the role of reflex activity in spasticity and the relationship between peak passive torque, Ashworth Scale (AS), and Spasm Frequency Scale (SFS) of the knee flexors and extensors during the measurement of spasticity using an isokinetic dynamometer in children with spinal cord injury (SCI).. Eighteen children with chronic SCI and 10 children of typical development (TD) participated. One set of 10 passive movements was completed using an isokinetic dynamometer at 15, 90, and 180 degrees per second (deg/s) while surface electromyographic data were collected from the vastus lateralis (VL) and medial hamstrings (MH). Spasticity was clinically assessed using the AS and SFS.. There were no significant differences in peak passive torque of the knee flexors and extensors at any velocity for children with SCI compared to children with TD. Children with TD demonstrated significantly more reflex activity of the MH during the assessment of knee flexor spasticity at all movement velocities than did children with SCI. Children with TD demonstrated significantly more reflex activity of the VL during the assessment of knee-extensor spasticity with movements at 180 deg/s. The relationship between peak passive torque, AS, and SFS was significant during movements at a velocity of 90 deg/s only.. The role of increased reflexes in spasticity needs further examination. Isokinetic dynamometry may be measuring a different aspect of spasticity than the AS and SFS do in children with SCI.

Topics: Adolescent; Age Factors; Child; Child, Preschool; Disability Evaluation; Electromyography; Female; Humans; Knee; Male; Muscle Contraction; Muscle Spasticity; Muscle Strength Dynamometer; Muscle, Skeletal; Neurologic Examination; Paralysis; Predictive Value of Tests; Range of Motion, Articular; Spinal Cord Injuries; Torque

The interpretation of the results of previous anti-osteoporosis interventions after spinal cord injury (SCI) is undermined by incomplete information about the intervention dose or patient adherence to dose requirements. Rehabilitation research as a whole traditionally has struggled with these same issues. The purpose of this case report is to offer proof of the concepts that careful dose selection and surveillance of patient adherence should be integral components in rehabilitation interventions.. A 21-year-old man with T4 complete paraplegia (7 weeks) enrolled in a unilateral soleus muscle electrical stimulation protocol. Compressive loads applied to the tibia approximated 1.4 times body weight. Over 4.8 years of home-based training, data logging software provided surveillance of adherence. Soleus muscle torque and fatigue index adaptations to training as well as bone mineral density (BMD) adaptations in the distal tibia were measured.. The patient performed nearly 8,000 soleus muscle contractions per month, with occasional fluctuations. Adherence tracking permitted intervention when adherence fell below acceptable values. The soleus muscle torque and fatigue index increased rapidly in response to training. The BMD of the untrained tibia declined approximately 14% per year. The BMD of the trained tibia declined only approximately 7% per year. The BMD was preferentially preserved in the posterior half of the tibia; this region experienced only a 2.6% annual decline.. Early administration of a load intervention, careful estimation of the loading dose, and detailed surveillance of patient adherence aided in the interpretation of a patient's adaptations to a mechanical load protocol. These concepts possess wider applicability to rehabilitation research and should be emphasized in future physical therapy investigations.

Topics: Adaptation, Physiological; Adult; Electric Stimulation Therapy; Humans; Male; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Osteoporosis; Paraplegia; Patient Compliance; Spinal Cord Injuries; Tibia; Torque

To describe a standard clinical protocol for the objective assessment of manual wheelchair propulsion; to establish preliminary values for temporal and kinetic parameters derived from the protocol; and to develop graphical references and a proposed application process for use by clinicians.. Case series.. Six research institutions that collect kinetic wheelchair propulsion data and contribute that data to an international data pool.. Subjects with spinal cord injury (N=128).. Subjects propelled a wheelchair from a stationary position to a self-selected velocity across a hard tile surface, a low pile carpet, and up an Americans with Disabilities Act-compliant ramp. Unilateral kinetic data were obtained from subjects using a force and moment sensing pushrim.. Differences in self-selected velocity, peak resultant force, push frequency, and stroke length across all surfaces, relationship between (1) weight-normalized peak resultant force and self-selected velocity and (2) push frequency and self-selected velocity.. Graphical references were generated for potential clinical use based on the relation between body weight-normalized peak resultant force, push frequency, and velocity. Self-selected velocity decreased (ramp < carpet < tile), peak resultant forces increased (ramp > carpet > tile), and push frequency and stroke length remained unchanged when compared across the different surfaces. Weight-normalized peak resultant force was a significant predictor of velocity on tile and ramp. Push frequency was a significant predictor of velocity on tile, carpet, and ramp.. We present preliminary data generated from a clinically practical manual wheelchair propulsion evaluation protocol and we describe a proposed method for clinicians to objectively evaluate manual wheelchair propulsion.

Topics: Adult; Analysis of Variance; Architectural Accessibility; Equipment Design; Ergometry; Female; Floors and Floorcoverings; Humans; Kinetics; Linear Models; Male; Materials Testing; Movement; Spinal Cord Injuries; Surface Properties; Torque; Wheelchairs

With long-term electrical stimulation training, paralyzed muscle can serve as an effective load delivery agent for the skeletal system. Muscle adaptations to training, however, will almost certainly outstrip bone adaptations, exposing participants in training protocols to an elevated risk for fracture. Assessing the physiological properties of the chronically paralyzed quadriceps may transmit unacceptably high shear forces to the osteoporotic distal femur. We devised a two-pulse doublet strategy to measure quadriceps physiological properties while minimizing the peak muscle force. The purposes of the study were 1) to determine the repeatability of the doublet stimulation protocol, and 2) to compare this protocol among individuals with and without spinal cord injury (SCI). Eight individuals with SCI and four individuals without SCI underwent testing. The doublet force-frequency relationship shifted to the left after SCI, likely reflecting enhancements in the twitch-to-tetanus ratio known to exist in paralyzed muscle. Posttetanic potentiation occurred to a greater degree in subjects with SCI (20%) than in non-SCI subjects (7%). Potentiation of contractile rate occurred in both subject groups (14% and 23% for SCI and non-SCI, respectively). Normalized contractile speed (rate of force rise, rate of force fall) reflected well-known adaptations of paralyzed muscle toward a fast fatigable muscle. The doublet stimulation strategy provided repeatable and sensitive measurements of muscle force and speed properties that revealed meaningful differences between subjects with and without SCI. Doublet stimulation may offer a unique way to test muscle physiological parameters of the quadriceps in subjects with uncertain musculoskeletal integrity.

Topics: Adaptation, Physiological; Adult; Electric Stimulation; Exercise Test; Female; Femoral Fractures; Humans; Male; Middle Aged; Muscle Contraction; Muscle Strength; Paralysis; Quadriceps Muscle; Reproducibility of Results; Spinal Cord Injuries; Stress, Mechanical; Torque

The flexion reflex in human spinal cord injury (SCI) is believed to incorporate interneuronal circuits that consist elements of the stepping generator while ample evidence suggest that hip proprioceptive input is a controlling signal of locomotor output. In this study, we examined the expression of the non-nociceptive flexion reflex in response to imposed sinusoidal passive movements of the ipsilateral hip in human SCI. The flexion reflex was elicited by low-intensity stimulation (300 Hz, 30 ms pulse train) of the right sural nerve at the lateral malleolus, and recorded from the tibialis anterior (TA) muscle. Sinusoidal hip movements were imposed to the right hip joint at 0.2 Hz by a Biodex system while subjects were supine. The effects of leg movement on five leg muscles along with hip, knee, and ankle joint torques were established simultaneously with the modulation pattern of the flexion reflex during hip oscillations. Phase-dependent modulation of the flexion reflex was present during hip movement, with the reflex to be significantly facilitated during hip extension and suppressed during hip flexion. The phase-dependent flexion reflex modulation coincided with no changes in TA pre- and post-stimulus background ongoing activity during hip extension and flexion. Reflexive muscle and joint torque responses, induced by the hip movement and substantiated by excitation of flexion reflex afferents, were entrained to specific phases of hip movement. Joint torque responses were consistent with multi-joint spasmodic muscle activity, which was present mostly during the transition phase of the hip from flexion to extension and from mid- to peak extension. Our findings provide further evidence on the interaction of hip proprioceptors with spinal interneuronal circuits engaged in locomotor pathways, and such interaction should be considered in rehabilitation protocols employed to restore sensorimotor function in people with SCI.

Topics: Adult; Ankle Joint; Electric Stimulation; Female; Hip; Hip Joint; Humans; Knee Joint; Male; Middle Aged; Movement; Muscle, Skeletal; Proprioception; Reflex; Spasm; Spinal Cord Injuries; Sural Nerve; Torque

To test the hypothesis that pushing on a cross slope leads to increased handrim loading compared with that found on a level surface.. Case series.. Biomechanics laboratory.. Twenty-six manual wheelchair users.. Subjects pushed their own wheelchairs on a research treadmill set to level, 3 degrees , and 6 degrees cross slopes. Propulsion speed was self-selected for each cross-slope condition. Handrim biomechanics were measured for the downhill wheel, using an instrumented wheelchair wheel and a motion capture system.. Speed, peak kinetics (force, rate of loading, torque), push angle, cadence, push distance, and power output were averaged over a 20-push set for each subject and each cross-slope condition. Outcomes were compared across cross slopes using a repeated-measures analysis of variance.. Push angle and cadence were unaffected by cross slope. A trend of decreasing self-selected speeds with increasing cross slope was not significant. There were considerable increases in the peak kinetic measures, with the axial moment increasing by a factor of 1.8 on the 6 degrees cross slope (P=.000). More pushes were required to cover the same distance when on a cross slope (P<.034). The power required for propulsion increased by a factor of 2.3 on the 6 degrees cross slope (P=.000).. Users must push harder when on a cross slope. This increased loading is borne by the users' arms, which are at risk for overuse injuries. Exposure to biomechanic loading can be reduced by avoiding cross slopes when possible.

Topics: Acceleration; Adult; Analysis of Variance; Arm; Arm Injuries; Biomechanical Phenomena; Cumulative Trauma Disorders; Equipment Design; Exercise Test; Female; Hand Strength; Humans; Linear Models; Male; Muscle Strength Dynamometer; Psychomotor Performance; Risk Factors; Sample Size; Spinal Cord Injuries; Statistics, Nonparametric; Task Performance and Analysis; Torque; Wheelchairs

To determine the efficacy of using modulated middle frequency alternating current (MFAC) muscle stimulation for functional electric stimulation-propelled cycling by people with spinal cord injury (SCI) compared with the conventional method of using standard low-frequency rectangular pulses (LFRP).. Repeated-measures.. Laboratory setting.. Eleven otherwise healthy volunteer subjects with SCI (8 with American Spinal Injury Association [ASIA] grade A, 3 with ASIA grade B).. To evaluate cycling-relevant differences between LFRP and modulated MFAC stimulation, we exposed participants to isometric measurements and cycling experiments performed during both 20 Hz LFRP and 4 KHz modulated with 50 Hz MFAC.. We recorded maximal isometric torque, maximal dynamic work during 20 minutes of ergometer cycling, and perceived discomfort for each of the 2 stimulation patterns.. Both the isometric torque (P<.02) and work generated (P<.001) during MFAC stimulation were significantly lower than during standard LFRP stimulation. Four participants reported discomfort and 1 of them also developed skin burns during MFAC stimulation.. Our findings suggest that in SCI subjects, stimulated cycling with low frequency is generally more effective than cycling with modulated MFAC in terms of torque, work, and pain sensation.

Topics: Adolescent; Adult; Bicycling; Electric Stimulation Therapy; Ergometry; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle Fatigue; Muscle, Skeletal; Pain Measurement; Spinal Cord Injuries; Torque

Motor evoked potential (MEP) amplitudes have the disadvantage of a high variability when repeatedly assessed. This affects the reliability of MEP amplitude measurements taken during the course of motor incomplete spinal cord injury (iSCI). The study investigated the reliability of anterior tibial (TA) MEP measures controlled for dorsal flexion torque and motor task.. TA MEPs were recorded at 10, 20, 40 and 60% of maximal voluntary contraction (MVC) during a static and dynamic (isometric increase of dorsal flexion torque) motor task. To determine reliability, 20 healthy and five chronic iSCI subjects were tested twice (> or =7 days) by the same investigator. Intraclass correlation coefficients (ICCs) were calculated. MEP amplitudes and latencies were compared between 20 healthy and 29 iSCI subjects.. The reliability of MEP amplitude was in general good (ICC > or = 0.52) and was highest during the static task at 40% MVC (ICC = 0.77). The increased facilitation by the dynamic motor task showed the best reliability at 20% MVC (ICC = 0.48). The reliability was good to excellent for MEP latency (0.46 < or = ICC < or = 0.81), MVC (ICC > or = 0.90) and for the TMS threshold required to evoke a MEP response (ICC > or = 0.77). The torque generated by the MEP response ()0.02 < or = ICC < or = 0.55) and the duration of the silent period (0.07 < or = ICC < or = 0.50) were not reliable. Both MEP amplitudes and latencies differed significantly between healthy and iSCI subjects.. Controlling for torque generation and motor task establishes a reliability of TA MEP amplitudes that is sufficient for longitudinal assessments in motor incomplete SCI.

Topics: Adult; Analysis of Variance; Electric Stimulation; Electromyography; Evoked Potentials, Motor; Humans; Leg; Male; Middle Aged; Motor Activity; Muscle, Skeletal; Reaction Time; Reference Values; Reproducibility of Results; Spinal Cord Injuries; Task Performance and Analysis; Torque; Transcranial Magnetic Stimulation

The aim of this study was to investigate the change in body composition, leg girths, and muscle strength of patients with incomplete spinal cord injury (SCI) after functional electrical stimulation cycling exercises (FESCE). Eighteen subjects with incomplete SCI were recruited. Each patient received FESCE three times per week for 8 weeks. Body composition, thigh and calf girths of bilateral legs, muscle strength of bilateral knee flexors and extensors were measured before and after 4 and 8 weeks of FESCE. A significant increase in bilateral thigh girth after 4 weeks of FESCE and significant increase in muscular peak torque of knee flexion and extension were found after 8 weeks of training. Besides, lean body mass increased significantly after complete treatment. FESCE can increase the thigh girth and muscular peak torque of patients with incomplete spinal cord injury.

Topics: Adult; Body Composition; Body Mass Index; Electric Stimulation; Female; Humans; Male; Middle Aged; Spinal Cord Injuries; Torque

The aim of this study was to investigate the influence of hip proprioceptors on the organisation of the flexor reflex elicited by nociceptive stimulation in individuals with spinal cord injury. The influence of hip position and passive movement were tested in 10 subjects with chronic spinal cord injury. Stimuli were tested isometrically with the hip in three positions. Additionally, the response was also measured to stimuli applied with the hip at midposition during imposed hip flexion and extension movement. The torque and EMG responses were compared in order to identify the postural and movement-dependent modulation of the withdrawal reflex. Ankle and hip torques were significantly modulated by hip position (ANOVA, p<0.05), with the largest torque response obtained in the hip extended position, compared with the flexed position. We also observed a significant difference between the flexor reflex during movement and with the leg isometric. Ankle and hip torque and tibialis anterior electromyograms were significantly higher in the movement conditions than the isometric condition (Tukey test, p<0.05). We postulate that inputs from hip proprioceptors enhance the withdrawal reflex response. Movement appears to increase the response, regardless of movement direction, suggesting a novel role for the dynamic components of hip afferents.

Topics: Adolescent; Adult; Ankle Joint; Chronic Disease; Electric Stimulation; Electromyography; Hip Joint; Humans; Middle Aged; Muscle Contraction; Neurons, Afferent; Nociceptors; Posture; Proprioception; Range of Motion, Articular; Reflex; Spinal Cord Injuries; Torque

Hypersensitivity of the flexor reflex pathways to input from force-sensitive muscle afferents may contribute to the prevalence and severity of muscle spasms in patients with spinal cord injury (SCI). In this study, we triggered flexor reflexes with constant velocity knee movements in 15 subjects with SCI. Ramp and hold knee extension perturbations were imposed on one leg while the hip and ankle were held in an isometric position using an instrumented leg brace. Knee, ankle and hip torque responses and electromyograms from six muscles of the leg were recorded following controlled knee extension at four different velocities. Tests were conducted with the hip in both flexed and extended positions. During the movement into knee extension, a velocity-dependent stretch reflex, represented by a progressively increasing knee flexion torque, was observed. In addition, another type of reflex that resembled a flexor reflex (flexion of the hip and ankle) was also triggered by the imposed knee extension. The magnitude of the ankle dorsiflexion torque responses was significantly correlated to the stretch reflex torque at the knee in 9 of the 15 subjects. We concluded that stretch reflexes initiate a muscle contraction that then can contribute to a flexor reflex response, possibly through muscle group III/IV afferent pathways. These results suggest that spasticity in SCI consists of a myriad of complex reflex responses that extend beyond stretch reflexes.

Topics: Adult; Afferent Pathways; Chronic Disease; Electromyography; Humans; Knee; Mechanoreceptors; Middle Aged; Movement; Muscle Contraction; Muscle, Skeletal; Physical Stimulation; Quadriceps Muscle; Reflex, Abnormal; Spasm; Spinal Cord; Spinal Cord Injuries; Torque

A cross-sectional study design.. To characterize and specifically quantify impairments in muscle function after chronic incomplete spinal cord injury (SCI).. University of Florida, Gainesville, FL, USA.. Voluntary and electrically elicited contractile measurements were performed and voluntary activation deficits were quantitatively determined in the knee extensor and ankle plantar flexor muscle groups in 10 individuals with chronic incomplete SCI (C5-T8, ASIA C or D) and age-, gender-, height- and body weight matched healthy controls.. Persons with incomplete-SCI were able to produce only 36 and 24% of the knee extensor torque and 38 and 26% of the plantar flexor torque generated by noninjured controls in the self-reported less-involved and more-involved limbs, respectively (P<0.05). In addition, both indices of explosive or instantaneous muscle strength, torque200 (absolute torque reached at 200 ms) and the average rate of torque development (ARTD) were dramatically reduced in the ankle plantar flexor and knee extensor muscle groups in persons with incomplete-SCI. However, the deficit in instantaneous muscle strength was most pronounced in the ankle plantar flexor muscles, with an 11.7-fold difference between the torque200 measured in the self-reported more involved limb and a 5-fold difference in the less-involved limb compared to control muscles. Voluntary activation deficits ranged between 42 and 66% in both muscle groups. Interestingly, electrically elicited contractile properties did not differ between the groups.. The resultant impact of incomplete-SCI is that affected muscles not only become weak, but slow to develop voluntary torque. We speculate that the large deficit in torque200 and ARTD in the ankle plantar flexors muscles of persons with incomplete-SCI may limit locomotor function. The results presented in this study provide a quantitative and sensitive assessment of muscle function upon which future research examining rehabilitation programs aimed at restoring muscle function and promoting functional recovery after incomplete-SCI may be based.

Topics: Adult; Case-Control Studies; Electromyography; Female; Humans; Lower Extremity; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Postural Balance; Spinal Cord Injuries; Time Factors; Torque

Manual wheelchair users rely heavily on their upper limbs for independent mobility which likely leads to a high prevalence of shoulder pain and injury. The goal of this study was to examine the relationship between shoulder forces and moments experienced during wheelchair propulsion and shoulder pathology.. Kinetic and kinematic data was recorded from 33 subjects with paraplegia as they propelled their wheelchairs at two speeds (0.9 and 1.8 m/s). Shoulder joint forces and moments were calculated using inverse dynamic methods and shoulder pathology was evaluated using a physical exam and magnetic resonance imaging scan.. Subjects who experienced higher posterior force (Odds Ratio (OR)=1.29, P=0.03), lateral force (OR=1.35, P=0.047), or extension moment (OR=1.35, P=0.09) during propulsion were more likely to exhibit coracoacromial ligament edema. Individuals who displayed larger lateral forces (OR=4.35, P=0.045) or abduction moments (OR=1.58, P=0.06) were more likely to have coracoacromial ligament thickening. Higher superior forces (OR=1.05, P=0.09) and internal rotation moments (OR=1.61 P=0.02) at the shoulder were associated with increased signs of shoulder pathology during the physical exam.. Specific joint forces and moments were related to measures of shoulder pathology. This may indicate a need to reduce the overall force required to propel a wheelchair in order to preserve upper limb integrity. Potential interventions include changes to wheelchair setup, propulsion training, or alternative means of mobility.

Topics: Adult; Aged; Anthropometry; Biomechanical Phenomena; Female; Humans; Kinetics; Male; Middle Aged; Muscle, Skeletal; Shoulder; Shoulder Joint; Spinal Cord Injuries; Torque; Wheelchairs

A three-dimensional (3D) biomechanical model was developed to determine upper extremity kinematics and kinetics of persons walking with forearm crutches. Six-component load cells and strain gauges were installed in the crutches to determine crutch forces. A six-camera VICON motion system was used to acquire coordinate data from 24 reflective markers attached to the upper extremities and crutches. Joint axes for the wrist, elbow, and glenohumeral joints were defined and joint forces and moments were determined using inverse dynamics. Accuracy of the crutch instrumentation was established by simultaneously collecting force data from a Kistler forceplate and each crutch during crutch-assisted gait with the respective crutch tip contacting the forceplate. In order to demonstrate the application of this biomechanical model, upper extremity weight bearing forces, joint motion, and stride characteristics were recorded from a subject with T-12 incomplete spinal cord injury (SCI), using a crutch-assisted reciprocal four-point gait pattern. The peak net joint forces and moments were greater for the right arm opposite the weaker left lower extremity. The largest joint forces were directed superiorly (Fz) and the asymmetrical pattern of crutch use was consistent with lower extremity strength differences. During left leg weight acceptance, increased right wrist extension motion and moment were recorded, which may contribute to wrist pathology.

Topics: Aged; Biomechanical Phenomena; Crutches; Diagnosis, Computer-Assisted; Equipment Failure Analysis; Gait Disorders, Neurologic; Humans; Kinetics; Male; Movement; Muscle Contraction; Muscle, Skeletal; Spinal Cord Injuries; Stress, Mechanical; Torque; Treatment Outcome; Upper Extremity

Muscles of individuals with a spinal cord injury (SCI) exhibit an unexpected leftward shift in the force (torque)-frequency relationship. We investigated whether differences in torque-angle relationships between SCI and able-bodied control muscles could explain this shift. Electrically stimulated knee-extensor contractions were obtained at knee flexion angles of between 30 degrees and 90 degrees. Torque-frequency relationships were obtained at 30 degrees, 90 degrees, and optimum angle. Optimum angle was not different between groups but SCI-normalized torques were lower at the extreme angles. At all angles, SCI muscles produced higher relative torques at low stimulation frequencies. Thus, there was no evidence of a consistent change in the length of paralyzed SCI muscles, and the anomalous leftward shift in the torque-frequency relationship was not the result of testing the muscle at a relatively long length. The results provide valuable information about muscle changes occurring in various neurological disorders.

Topics: Adult; Electric Stimulation; Humans; Knee Joint; Male; Movement; Muscle Contraction; Muscle, Skeletal; Paralysis; Spinal Cord Injuries; Torque

Manual wheelchair users have been found to be at risk for secondary upper extremity injuries.. The primary goal of this study was to compare shoulder strength and muscle imbalance of individuals with paraplegia to case-wise matched unimpaired controls (UC). A secondary goal was to evaluate the impact of age and neurologic level of injury (NLI) on weight-normalized strength (WNS).. The SCI group (n = 28) and the UC group (n = 28) completed bilateral shoulder isokinetic strength testing in the sagittal, frontal, and horizontal plane at 60 degrees/second using the BioDex system. Strength ratios, an indicator of muscle imbalance, were also calculated.. No significant difference was seen in shoulder strength or strength ratios between the SCI group and the UC group. However, NLI was significantly related to WNS on several planes in the SCI group. Therefore, we dichotomized the SCI group into equal groups based on an NLI. The Low-SCI group was significantly stronger than the High-SCI group in most planes (P < 0.05). The High-SCI group was significantly weaker than the UC in extension (P < 0.01) and a trend (P < 0.01) was seen in flexion, abduction, and external rotation. The Low-SCI group was significantly stronger in abduction than the UC.. WNS at the shoulder correlated with NLI. It is likely that this is related to contributions of the trunk and abdominal muscles during testing, since proximal trunk strength aids in generating forces distally. This study and others of strength in individuals with paraplegia may overestimate shoulder strength.

Topics: Adult; Age Factors; Arm; Case-Control Studies; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle, Skeletal; Paraplegia; Range of Motion, Articular; Shoulder Joint; Spinal Cord Injuries; Torque; Wheelchairs

The current study compared the intralimb coordination of flexor reflex responses in spinal intact and complete chronic spinal cord injured (SCI) individuals. Noxious electrocutaneous stimulation was applied at the apex of the medial arch of the foot (50 mA, 500 Hz, 1 ms pulse width, 20 ms) in 21 complete chronic SCI and 19 spinal intact volunteers and the flexor reflex response was quantified by measuring the isometric joint torques at the ankle, knee and hip. The results showed that SCI individuals had significantly smaller peak knee and hip joint flexion torques, often exhibited a net knee extension torque, and produced a much smaller hip joint flexion torque during the flexor reflex response in contrast to the spinal intact individuals. The latency of the reflex response, measured from the tibialis anterior electromyogram, was comparable in both test populations. These findings indicate that the intralimb coordination of the flexor reflex response of chronic complete SCI individuals is altered, possibly reflecting a functional reorganization of the flexion pathways of the spinal cord.

Topics: Chronic Disease; Electromyography; Humans; Joints; Leg; Movement Disorders; Muscle Contraction; Muscle, Skeletal; Neural Pathways; Neuronal Plasticity; Reaction Time; Reflex, Abnormal; Spinal Cord; Spinal Cord Injuries; Torque

To evaluate the effects of percutaneous electric stimulation on knee extensor strength and muscle hypertrophy, gait, and energy cost of walking in a young man with partial denervation of the knee extensors.. One-way repeated measures.. Pediatric orthopedic hospital.. A man in his early twenties, who had an L2 American Spinal Injury Association class D spinal cord injury, presented with strength deficits in his left knee extensors and reported falling frequently. When walking, his left knee remained locked in extension throughout stance. Electromyographic testing revealed chronic denervation and reinnervation changes.. Because of sensory difficulties with surface stimulation, a percutaneous electrode was surgically implanted near the femoral nerve. The subject exercised isometrically with a research grade stimulator for 1 hour a day until his strength plateaued.. Quadriceps femoris strength and hypertrophy, gait, and energy cost of walking were recorded preintervention, every 2 months during the strengthening phase, and 2 months after withdrawal.. Voluntary isometric torque improved from 7 to 14.8Nm (112%) and decreased to 8.5Nm after stimulation was withdrawn. Mean circumferential measures of the thigh improved from 12.3 to 13.5cm (9.8%) and then decreased to 13.1cm. Gait kinematics and kinetics were unchanged, although the subject reported greater stability in his left knee and fewer falls.. The study indicates that percutaneous electric stimulation could be used to strengthen partially denervated muscle and to affect function. However, gains in strength may not be maintained once treatment is withdrawn.

Topics: Adult; Analysis of Variance; Humans; Knee; Male; Muscle Denervation; Muscle, Skeletal; Muscular Atrophy; Spinal Cord Injuries; Torque; Transcutaneous Electric Nerve Stimulation; Walking

To develop a method for assessment of spasticity, in which the whole range of motion (ROM) at a wide variation of speeds is applied.. Cross-sectional design to study construct validity.. Research department affiliated with a rehabilitation hospital in The Netherlands.. Nine patients with complete spinal cord injury recruited from the rehabilitation hospital.. Not applicable.. Thirty to 45 stretches over the whole ROM were applied to the triceps surae muscle at varying velocities measuring from 30 degrees to 150 degrees/s. Electromyographic responses were measured in order to assess reflex excitability. The torque over the ankle joint was measured during the whole stretch. The angle and velocity at which the reflex was initiated was also determined.. The electromyographic responses increased significantly at increasing stretch velocities (P<.001). The applied maximum angles are reproducible (intraclass correlation coefficient, .81) and provide representative torque responses.. The assessment method of spasticity using full range passive movements provides objective outcomes. The angular velocity is responsible for an exponential increase in amplitude of the electromyographic response.

Topics: Adult; Cross-Sectional Studies; Electromyography; Female; Humans; Lower Extremity; Male; Muscle Spasticity; Range of Motion, Articular; Reflex, Stretch; Reproducibility of Results; Spinal Cord Injuries; Torque

Previous investigations have identified muscular imbalance in the shoulder as a source of pain and injury in manual wheelchair users. Our aim was to determine whether a correlation exists between strength and pushrim biomechanical variables including: tangential (motive) force (Ft), radial force (Fr), axial force (Fz), total (resultant) force (FR), fraction of effective force (FEF), and cadence.. Peak isokinetic shoulder strength (flexion [FLX], extension [EXT], abduction [ABD], adduction [ADD], internal rotation [IR], and external rotation [ER]) was tested in 22 manual wheelchair users with a BioDex system for 5 repetitions at 60 degrees/s. Subjects then propelled their own manual wheelchair at 2 speeds, 0.9 m/s (2 mph) and 1.8 m/s (4 mph), for 20 seconds, during which kinematic (OPTOTRAK) and kinetic (SMARTWHEEL) data were collected. Peak isokinetic forces in the cardinal planes were correlated with pushrim biomechanical variables.. All peak torque strength variables correlated significantly (P < or = 0.05) with Ft, Fr, and FR, but were not significantly correlated with Fz, FEF, or cadence. Finally, there were no relationships found between muscle strength ratios (for example, FLX/EXT) and Ft, Fr, FR, Fz, or FEF.. There was a correlation between strength and force imparted to the pushrim among wheelchair users; however, there was no correlation found in wheelchair propulsion or muscle imbalance. Clinicians should be aware of this, and approach strength training and training in wheelchair propulsion techniques separately.

Topics: Adult; Biomechanical Phenomena; Data Interpretation, Statistical; Female; Humans; Male; Middle Aged; Muscle, Skeletal; Shoulder; Shoulder Pain; Spinal Cord Injuries; Torque; Wheelchairs

Individuals with chronic spinal cord injury (SCI) often demonstrate multijoint reflex activity that is clinically classified as an extensor spasm. These responses are commonly observed in conjunction with an imposed extension movement of the hips, such as movement from a sit to a supine position. Coincidentally, afferent feedback from hip proprioceptors has also been implicated in the control of locomotion in the spinalized cat. Because of this concurrence, we postulated that extensor spasms that are triggered by hip extension might involve activation of organized interneuronal circuits that also have a role in locomotion. If true, imposed oscillations of the hip would be expected to produce activity of the leg musculature in a locomotor pattern. Furthermore, this muscle activity would be entrained to the hip movement. The right hip joints of 10 individuals with chronic SCI, consisting of both complete [American Spinal Injury Association (ASIA) A] and incomplete (ASIA B,C) injuries, were subjected to ramp and hold (10 s) movements at 60 degrees /s and sinusoidal oscillations at 1.2, 1.88, and 2.2 rad/s over ranges from 40 to -15 degrees (+/-5 degrees ) using a custom servomotor system. Surface EMG from seven lower extremity muscles and sagittal-plane joint torques were recorded to characterize the response. Ramp and hold perturbations produced coactivation at the hip, knee, and ankle joints, with a long duration (5-10 s). Sinusoidal perturbations yielded consistent muscle timing patterns that resulted in alternating flexor and extensor joint torques. EMG and joint torques were commonly entrained to the frequency of movement, with rectus femoris, vastus medialis, and soleus activity coinciding with hip extension and medial hamstrings activity occurring during hip flexion. Individual muscle timing patterns were consistent with hip position during normal gait, except for the vastus medialis. These results suggest that reflexes associated with extensor spasms may occur through organized interneuronal pathways, such as spinal centers for locomotion.

Topics: Adult; Chronic Disease; Electromyography; Hip; Humans; Leg; Movement; Muscle, Skeletal; Oscillometry; Spinal Cord Injuries; Time Factors; Torque

The contribution of force-sensitive muscular afferents to prolonged flexion withdrawal reflexes, or flexor spasms, after human spinal cord injury (SCI) was investigated. In three separate experimental conditions, flexion reflexes were triggered in subjects with SCI using trains of electrocutaneous stimuli delivered at the foot and lower leg and compared with reflexes elicited via intramuscular (i.m.) electrical stimuli. In the first experiment, flexion reflexes were elicited using i.m. stimuli to the tibialis anterior (TA) in the majority of subjects tested. The ratio of peak isometric ankle to hip torques during i.m.-triggered reflexes were proportionally similar to those evoked by electrocutaneous foot or shank stimulation, although the latency to onset and peak flexion torques were significantly longer with i.m. stimulation. In the second experiments, the amplitude and frequency of i.m. TA stimulation were varied to alter the stimulus-induced muscle torque. Peak ankle and hip torques generated during the flexion reflex responses were correlated to a greater extent with stimulus-induced muscle torques as compared with the modulated stimulus parameters. In the third experimental series, i.m. stimuli delivered to the gastrocnemius (GS) elicited flexion reflexes in approximately half of the subjects tested. The combined data indicate a potentially prominent role of the stimulus-induced muscle contraction to the magnitude and latency of flexor reflex behaviors after i.m. TA stimulation. Results after i.m. GS stimulation indicate multi-joint flexion reflexes can also be elicited, although to a lesser extent than i.m. TA stimulation.

Topics: Adult; Electromyography; Female; Foot; Humans; Male; Middle Aged; Motor Neurons; Muscle Contraction; Muscle, Skeletal; Neurons, Afferent; Reflex; Skin; Spasm; Spinal Cord Injuries; Torque

This study investigated the effect of pedal cadence upon torque production, power output and muscle fatigue rates during functional electrical stimulation evoked cycling in spinal cord injured individuals.. All subjects had complete thoracic spinal cord injuries T4-T9 (ASIA A) and had been functional electrical stimulation training regularly for at least 6 months.. One trial (n = 8) examined a low vs high pedal rate (20 and 50 rev x min(-1)) upon isolated muscle fatigue over 5 minutes. A second trial (n = 9) investigated the effect of cadence (15 vs 50 rev x min(-1)) upon performance during 35-minutes of functional electrical stimulation evoked cycling.. Peak torque produced by left quadriceps decayed significantly faster at the higher pedal cadence, indicating a higher rate of muscle fatigue. Functional electrical stimulation cycling over 35 minutes also revealed that peak and average torques were significantly greater at the lower cadence. From 15 minutes onwards, power output was significantly higher at 50 rev x min(-1) FES-cycling, compared with 15 rev x min(-1).. The higher muscle forces observed during low cadence functional electrical stimulation cycling should offer improvements over traditional pedalling velocities for training leg strength in individuals with spinal cord injury.

Topics: Adult; Analysis of Variance; Bicycling; Electric Stimulation; Exercise Therapy; Female; Humans; Male; Middle Aged; Muscle Fatigue; Muscle, Skeletal; Spinal Cord Injuries; Torque

Functional neuromuscular stimulation (FNS) has the potential to enhance the capability for individuals with a spinal cord injury (SCI) to perform activities of daily living. Individuals with SCI have successfully used FNS to stand, but the transition from sitting to standing is often awkward and may require excessive amounts of arm support. The long-term goal of this research project is to provide stimulation patterns that reduce the demands on an FNS user's arms and provide a smooth, stable sit-to-stand transition. A multi-segment, dynamic model has been developed to simulate different combinations of stimulated muscles and stimulation patterns. The model includes individualized anthropometric parameters, active and passive muscle and joint mechanics, and arm support forces (experimentally measured or an assumed pattern). Stimulated muscle properties were derived using SIMM software (Musculographics, Chicago, IL), and the simulations were run in Matlab (Mathworks, Natick, MA). Initial simulation results have estimated that ramped stimulation of the vastus lateralis and semimembranosus muscles reduces the peak vertical arm support forces from 91% to 42% of body weight as compared to unassisted sit-to-stand. Kinematic results also suggested that the hand support forces remained excessive due to a lack of joint coordination and insufficient ankle joint stiffness. In further simulations, additional muscles will be stimulated to increase joint stiffness and stimulation patterns will be designed to mimic able-bodied sit-to-stand motions. This model will be validated and improved using results of sit-to-stand experiments with FNS users once an optimized set of muscles and stimulation patterns has been determined.

Topics: Arm; Computer Simulation; Electric Stimulation Therapy; Humans; Knee; Models, Biological; Movement; Muscle Contraction; Muscle, Skeletal; Posture; Spinal Cord Injuries; Torque; Weight-Bearing

To quantify the magnitude of stretch that physiotherapists apply to the hamstring muscles of people with spinal cord injury (SCI).. Repeated-measures design.. SCI unit in Australia.. Fifteen individuals with motor complete paraplegia or tetraplegia.. Twelve physiotherapists manually administered a stretch to the hamstring muscles of each subject. The stretch was applied by flexing the hip with the knee extended.. Applied hip flexor torque.. Therapists applied median hip flexor torques of between 30 and 68Nm, although some torques were as large as 121Nm. The stretch applied by different therapists to any 1 subject varied as much as 40-fold.. There is a large range of stretch torques provided by physiotherapists to patients with SCI. Some therapists provide stretch torques well in excess of those tolerated by individuals with intact sensation.

Topics: Activities of Daily Living; Adult; Australia; Clinical Competence; Exercise Therapy; Female; Hip Joint; Humans; Linear Models; Male; Muscle, Skeletal; Pliability; Practice Guidelines as Topic; Range of Motion, Articular; Spinal Cord Injuries; Thigh; Torque

Reciprocal walking orthoses are routinely used by thoracic lesion patients for ambulation using crutches. A primary reason for their prescription is to provide therapeutic benefit and improved independence. To achieve this, maximum efficiency of walking and acceptance of the device is necessary to promote long-term compliance. Lateral rigidity in the orthosis influences walking efficiency, but the structural properties of conventional techniques for producing a sufficiently rigid body brace makes them unattractive. Currently patients and clinicians are forced to choose between greater efficiency or cosmesis of the orthosis. Composite materials have the potential to permit the required rigidity in a structure that is less obtrusive. However, their material properties could lead to unsafe forms of failure unless suitable manufacturing methods are devised. It is therefore inappropriate to supply prototypes to patients for field evaluation until laboratory investigation of innovative production methods has ensured that the orthosis is safe. A production technique has been devised that is ostensibly suitable. Prototype body braces have been tested and have been shown to have improved structural properties and safe failure modes. A test programme implemented on a complete concept orthosis has confirmed that improved lateral rigidity can be achieved with a less obtrusive body brace, and that it will behave safely for long enough to permit field evaluation.

Topics: Braces; Elasticity; Equipment Design; Equipment Failure Analysis; Gait Disorders, Neurologic; Humans; Manufactured Materials; Materials Testing; Pilot Projects; Prosthesis Failure; Prosthesis Fitting; Spinal Cord Injuries; Stress, Mechanical; Torque; Walking; Weight-Bearing

Extensor spasms, which are a significant component of spasticity in spinal cord injury (SCI), were investigated in an attempt to identify the role that hip proprioceptors play in triggering an extensor reflex response. In ten SCI subjects, a controlled hip extension movement was imposed on one leg while the knee and ankle were held in an isometric position using an instrumented leg brace. Isometric joint torques of the hip, knee, and ankle were measured following a constant velocity (30 degrees /s), 45 degrees -75 degrees extension movement of the hip that was applied using the motor of a Biodex rehabilitation/testing system. Electromyograms (EMGs) from four to eight muscles were also recorded during the ten movement trials. The stereotypical torque response to an imposed hip extension consisted of hip flexion, knee extension, and ankle plantarflexion, although all components were not observed in every subject. EMGs indicated coactivation at the knee and ankle joints, with extensor activity generally outlasting flexor activity. These observations are consistent with clinical descriptions of extensor spasms. In contrast, the response to imposed hip flexion, which was observed in six of the ten subjects, comprised hip extension, knee flexion and ankle extension. This difference between the response to hip flexion and the response to extension indicates a specificity of the reflex, suggesting that organized pathways for coordinating leg movements are involved.

Topics: Adolescent; Adult; Aged; Ankle Joint; Electromyography; Hip Joint; Humans; Knee Joint; Middle Aged; Muscle Contraction; Muscle Spasticity; Muscle, Skeletal; Proprioception; Range of Motion, Articular; Reflex; Spinal Cord Injuries; Thigh; Torque

Progressive neurophysiological changes in the excitability of the pathways that subserved ankle extensor stretch reflexes were observed following midthoracic contusion. The purpose of the present study was to determine the nature and time course of velocity-dependent changes in the excitability of the ankle stretch reflex following T(8) contusion injury. These studies were conducted in adult Sprague-Dawley rats using a 10-g 2.5-cm weight drop onto the exposed thoracic spinal cord (using an NYU injury device and a MASCIS protocol). Velocity-dependent ankle torques and triceps surae EMGs were measured in awake animals over a broad range of rotation velocities (49-612 deg/sec) using instrumentation and protocol previously reported. EMGs and ankle torques were measured before and at weekly intervals following injury. Statistical tests of the data included within group repeated measures ANOVA and between group one-way ANOVA comparisons with time-matched control animals. An alternating pattern of significant increase followed by significant decrease in velocity-dependent ankle torque was observed during the first postinjury month. An increase of 33% in the peak torque and 24% in peak EMG magnitude at 612 deg/sec was observed in the first week. EMG burst amplitudes, that were timed-locked to the dynamic phase of the rotation, were observed to increase and decrease in a manner, which indicated that the changes in torque included stretch-evoked active contractions of the ankle extensors. During the second and third postinjury months, consistent 24-40% increases in the peak torques and 17-107% increases in the EMG magnitudes at the highest velocity were observed. No significant increases in torques were observed in the slowest rotation velocity in these periods.

Topics: Animals; Ankle Joint; Electromyography; Female; Gait; Motor Activity; Rats; Rats, Sprague-Dawley; Reflex, Stretch; Regression Analysis; Spinal Cord; Spinal Cord Injuries; Torque

We have reported earlier that externally imposed ankle movements trigger ankle and hip flexion reflexes in individuals with spinal cord injury (SCI). In order to examine the afferent mechanisms underlying these movement-triggered reflexes, controlled ankle movements were imposed in 17 SCI subjects. In 13 of these subjects, reflex torques were recorded at the hip, knee and ankle in response to 5 ankle movement ranges, and 4 movement speeds. Subjects were tested using both ankle plantarflexion and dorsiflexion movements. The principal outcome measure, peak hip flexion torque of the induced reflexes, was used for comparing the effects of movement range and speed on the reflex response. We found that movement-triggered reflexes were sensitive to the angular range of ankle deflection, but insensitive to the velocity of the movement. Movement amplitudes sufficient to trigger hip and ankle flexion were routinely associated with increases in ankle passive force, suggesting that force-sensitive receptors participated in the reflex response. However, increases in angular range also corresponded to increases in muscle length, making it difficult to distinguish whether the response was triggered by a load-sensitive receptor (e.g., Golgi tendon organ or muscle free nerve ending) or a position-sensitive receptor responsive to absolute ankle angle (e.g., muscle spindle secondary afferent). The absence of velocity dependence of the reflex suggested that spindle Ia afferents were not major contributors. These results suggest movement-triggered reflexes originate in muscle receptors that are sensitive to either absolute muscle length, to muscle force or to both. Although receptors that are sensitive to absolute muscle length cannot be excluded with certainty, the finding that reflex responses require that ankle movements elicit an increase in passive force argues for a prominent role of nonspindle mechanoreceptors, such as group III/IV muscle afferents. These afferents are activated preferentially as muscles are stretched to near maximum length, and they appear to have potent reflex effects in spinal cord injury.

Topics: Adolescent; Adult; Afferent Pathways; Ankle; Chronic Disease; Hip; Humans; Knee; Mechanoreceptors; Movement; Muscle Contraction; Muscle Spindles; Muscle, Skeletal; Physical Stimulation; Proprioception; Reflex; Reflex, Stretch; Skin; Spinal Cord; Spinal Cord Injuries; Torque; Weight-Bearing

Cycling by means of functional electrical stimulation (FES) is an attractive training method for individuals with paraplegia. The physiological benefits of FES are combined with the psychological incentive of independent locomotion. In addition, cycling has the advantage in that the generated muscle forces are converted into drive power with relatively high efficiency compared to other means of locomotion, e.g., walking. For the design of an appropriate cycling device and the development of optimal stimulation patterns, it has to be investigated how the geometry for FES cycling, influenced by individual parameters of the FES-generated drive torques and the magnitude of variations among subjects with paraplegia, can be optimized. This study shows the design of a freely adjustable test bed with additional motor drive which allows static and dynamic measurements of force components and drive torque at the crank. Furthermore, the influence of geometry and various individual parameters on FES pedaling can be tested for each subject individually. A pedal path realized by a three-bar linkage that was optimized according to preliminary simulations further increases leg cycling efficiency. Safety precautions avoid injuries in case of excessive forces, e.g., spasms. Test results illustrate the application of the test bed and measurement routines. A test series with four paraplegic test persons showed that the presented static and dynamic measurement routines allow to provide optimal stimulation patterns for individual paraplegic subjects. While pedaling with these optimal stimulation patterns only negligible negative active drive torques, due to active muscle forces, were applied to the crank and sufficient drive power was generated to power a cycle independently.

Topics: Adult; Bicycling; Electric Stimulation Therapy; Equipment Design; Humans; Male; Middle Aged; Muscle, Skeletal; Paraplegia; Spinal Cord Injuries; Torque

Mechanical changes underlying spastic hypertonia were explored using a parallel cascade system identification technique to evaluate the relative contributions of intrinsic and reflex mechanisms to dynamic ankle stiffness in healthy subjects (controls) and spastic, spinal cord injured (SCI) patients. We examined the modulation of the gain and dynamics of these components with ankle angle for both passive and active conditions. Four main findings emerged. First, intrinsic and reflex stiffness dynamics were qualitatively similar in SCI patients and controls. Intrinsic stiffness dynamics were well modeled by a linear second-order model relating intrinsic torque to joint position, while reflex stiffness dynamics were accurately described by a linear, third-order system relating half-wave rectified velocity to reflex torque. Differences between the two groups were evident in the values of four parameters, the elastic and viscous parameters for intrinsic stiffness and the gain and first-order cut-off frequency for reflex stiffness. Second, reflex stiffness was substantially increased in SCI patients, where it generated as much as 40% of the total torque variance, compared with controls, where reflex contributions never exceeded 7%. Third, differences between SCI patients and controls depended strongly on joint position, becoming larger as the ankle was dorsiflexed. At full plantarflexion, there was no difference between SCI and control subjects; in the mid-range, reflex stiffness was abnormally high in SCI patients; at full dorsiflexion, both reflex and intrinsic stiffness were larger than normal. Fourth, differences between SCI and control subjects were smaller during the active than the passive condition, because intrinsic stiffness increased more in controls than SCI subjects; nevertheless, reflex gain remained abnormally high in SCI patients. These results elucidate the nature and origins of the mechanical abnormalities associated with hypertonia and provide a better understanding of its functional and clinical implications.

Topics: Adult; Ankle Joint; Female; Humans; Linear Models; Male; Middle Aged; Movement; Muscle Contraction; Muscle Spasticity; Muscle Tonus; Muscle, Skeletal; Posture; Range of Motion, Articular; Reference Values; Reflex; Spinal Cord Injuries; Torque

In this study we examined the influence of complete spinal cord injury (SCI) on the mechanical characteristics of skeletal muscle in vivo within 6 months of the injury. Surface electrical stimulation (ES) was applied to the left m. quadriceps femoris of patients at 6, 11 and 24 weeks after injury. Surface ES was also applied to seven able-bodied controls (AB) at two time points 18 weeks apart. ES consisted of 2 bouts of 20, 1-s isometric contractions with 2 s and 2 min of rest between contractions and bouts, respectively. The time from 20-80% of peak torque (rise time) and the half relaxation time (1/2 RT) were determined for the first and for the last few contractions. Force loss over repeat contractions was greater in SCI than AB (27% vs 95%; P = 0.0001), and did not change over the 18-week period. Rise time did not change over repeat contractions, was not different between groups, and nor did it change over the 18-week period (range: 150-172 ms). 1/2 RT showed several group differences. Overall, 1/2 RT was longer at the beginning of ES in SCI than AB [mean (SE) 133 (15) ms vs 90 (6) ms, P = 0.037]. Slowing of relaxation time with force loss over repeat contractions was found in SCI at 24 weeks after injury [167 (18) ms, P = 0.016], but not at 6 [128 (14) ms] or 11 [145 (12) ms] weeks after injury. AB, in contrast, showed prolonged relaxation times, with force loss at both time points [115 (10) ms and 113 (11) ms; P = 0.0001]. The results indicate that SCI alters the relaxation but not contractile properties of mixed skeletal muscle within the first 24 weeks of injury. Altered calcium handling and contraction-induced fiber injury are suggested to explain the slower relaxation time per se, and the prolonged relaxation with force loss observed after SCI.

Topics: Adolescent; Adult; Electric Stimulation; Humans; Isometric Contraction; Middle Aged; Muscle Fatigue; Muscle Relaxation; Muscle, Skeletal; Spinal Cord Injuries; Time Factors; Torque

During multimicroelectrode stimulation within the cat L6 spinal cord, the number of electrodes activated, their separation distance, and the stimulus interleave time all influenced isometric knee joint extension torque. The torque evoked by stimulation with a three electrode combination could be enhanced or suppressed when compared with that evoked by single or paired electrode stimulation. A similar difference was noted when comparing two electrode combination versus single electrode stimulation. Relative fatigue was not improved significantly by interleaving the stimuli from two or three microelectrodes. Compared with the extension torque response evoked by noninterleaved stimulation, torque evoked by interleaved stimulation with the two microelectrode combination was decreased when the electrode distance was 2.0 mm or less and increased when the electrode distance was 3.0 mm. Designing an optimal stimulation strategy for multimicroelectrode spinal cord stimulation will be challenging and complex if a suppression effect among these electrodes is to be avoided. To reduce muscle fatigue, an asynchronous, interleaved strategy of stimulation may be required.

Topics: Animals; Cats; Disease Models, Animal; Electric Stimulation Therapy; Electromyography; Knee Joint; Lumbar Vertebrae; Male; Microelectrodes; Muscle Contraction; Muscle Fatigue; Random Allocation; Range of Motion, Articular; Reaction Time; Sacrum; Spinal Cord; Spinal Cord Injuries; Time Factors; Torque

Hypersensitivity of the flexor reflexes to input from force-sensitive muscle afferents may contribute to the prevalence and severity of muscle spasms in patients with spinal cord injuries. In the present study, we triggered flexor reflexes with constant-velocity ankle movements into end-range dorsiflexion and plantarflexion positions in 8 individuals with spinal cord injuries. We found that all 8 subjects had coordinated increases in flexion torque at the hip and ankle following externally imposed plantarflexion movements at the ankle. In addition, end-range dorsiflexion movements also triggered flexor reflexes in 3 subjects, although greater loads were required to trigger such reflexes using dorsiflexion movements (compared to plantarflexion movements). These three-joint reflex torque patterns triggered by ankle movement were broadly comparable to flexion withdrawal responses elicited by electrocutaneous stimuli applied to a toe, although the amplitude of the torque response was generally lower. We conclude that excitation of muscle and joint-related afferents induced by end-range movements may be responsible for exaggerated flexion reflex responses in spinal cord injury.

Topics: Adult; Ankle Joint; Electromyography; Electrophysiology; Hip Joint; Humans; Leg; Middle Aged; Movement; Muscle, Skeletal; Reflex; Rotation; Spasm; Spinal Cord Injuries; Torque

We examined ankle clonus in four spastic subjects to determine whether this oscillatory behavior has the properties of a limit cycle, and whether it is driven by peripheral sensory input or by a spinal generator. Using Floquet Theory and Poincare sections to assess reflex stability, we found that cycle-to-cycle variability was small, such that the Floquet multipliers were always less than unity. Furthermore, the steady-state periodic orbit was not dependent on the initial position of the ankle. Both of these findings, coupled with strong correlations between the size of the applied load and the frequency of ankle movements and electromyogram burst frequency suggests that clonus behaves as a locally stable limit cycle driven from peripheral receptors. To better understand how nonlinear elements might produce stable oscillatory motion, we simulated the ankle stretch reflex response. We found that delays in the pathway caused the reflex to come on during the shortening phase of movement, so the additional reflex torque required to sustain oscillatory ankle movements was quite small. Furthermore, because the resistance to stretch is largely due to passive mechanics whose properties are quite stationary, the system is robust to small perturbations within the reflex pathway.

Topics: Adult; Ankle; Biomechanical Phenomena; Computer Simulation; Electromyography; Humans; Male; Models, Biological; Muscle Spasticity; Nonlinear Dynamics; Periodicity; Range of Motion, Articular; Reflex, Stretch; Signal Processing, Computer-Assisted; Spinal Cord Injuries; Torque

The quadriceps muscles of neurologically intact and spinal cord injured (SCI) human subjects were stimulated with constant current pulses. Up to three, separately adjustable stimulating electrodes over the motor points for vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF) muscles were used to maximize torque generation while minimizing discomfort. The torque generated by stimulation increased as the knee was slowly flexed to about 1 rad (50-60 degrees) and decreased beyond that point (a 'negative slope' on a torque-angle curve). Despite this region of negative slope the force generated by small oscillations remained positively correlated to the angle changes. When the knee was slowly extended again from a flexed position, the torque continued to decline and therefore showed a large degree of 'hysteresis'. Of the three heads studied, only stimulation of RF muscle generally produced this behavior. VL and VM had torques that increased monotonically with knee flexion over the range studied. The torques generated with electrical stimulation of normal subjects represented up to about 30% of maximum voluntary contraction. When subjects generated similar torques voluntarily, the negative slope region and substantial hysteresis were not observed. Thus, SCI subjects may be adversely affected by hysteresis during electrically-induced transitions from sitting to standing and vice versa, while normal subjects are not.

Topics: Adult; Biomechanical Phenomena; Elasticity; Electric Stimulation; Electromyography; Female; Humans; Knee Joint; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Oscillometry; Posture; Range of Motion, Articular; Spinal Cord Injuries; Thigh; Torque; Viscosity

The use of electrical stimulation for denervated muscles is still considered to be a controversial issue by many rehabilitation facilities and medical professionals because prior clinical experience has shown that treating denervated muscle tissue using exponential current over a long time period constitutes an impossible task. Despite this fact, we managed to evoke tetanic contractions in denervated muscle using a long duration stimulation with anatomically shaped electrodes and sufficiently high amplitudes. The pulse amplitudes, which were being used for this purpose, exceeded by far the MED-GV and EC regulations (300 mJ/impulse). For this reason, an application has recently been submitted to have the EC regulations changed accordingly. It takes a tetanic contraction to achieve the desired muscle fiber tension, constituting a hypertrophic stimulus. It is also an appropriate means of exercise, which is capable of creating the metabolic and structural conditions needed (e.g, increased mitochondrial volume and capillary density) to obtain satisfactory muscle performance. With patients suffering from a complete spinal cord injury at level D12/L1, having motor and sensory loss in both lower extremities, we were able to train denervated muscle using long-duration stimulation, evoking single muscle contractions at first, soon followed by tetanic contractions against gravity. To increase the efficacy of this functional electrical stimulation (FES) strengthening program, we used ankle weights. With daily FES training over a period of 1-2 years, denervated muscle was exercised until it produced torques between 16 and 38 Nm in the m. quadriceps. With that muscle force, it is possible to stand up from a sitting position in parallel bars. Our results show that denervated muscle in humans is indeed trainable and can perform functional activities with FES. Furthermore, this method of stimulation can assist in decubitus prevention and significantly improve the mobility of paraplegics.

Topics: Capillaries; Electric Stimulation Therapy; Electrodes; Exercise; Gravitation; Humans; Mitochondria, Muscle; Muscle Contraction; Muscle Fibers, Skeletal; Muscle, Skeletal; Paraplegia; Posture; Pressure Ulcer; Spinal Cord Injuries; Torque; Weight Lifting; Weight-Bearing

To assess resistance to passive isokinetic movements at specified speeds and range of motion, as a measure of muscular tonus.. A group of 12 subjects with complete traumatic spinal cord injury and a group of 12 able-bodied subjects were analysed, distinguishing the level of spasticity in the SCI group. Maximum eccentric peak torque was observed in passive isokinetic flexion (F) and extension (E) knee movement in displacements of 30, 60 and 120 per second.. The Student t-test showed that the average torque in the injured group was significantly higher than in the control group (F= 120 degrees per second, P<0.001). Variance analysis showed that the lower level presented lower torque levels (E=60 and 120 degrees per second, P<0.032), while those in the higher level presented higher torque levels (F and E=60 and 120 per second, P<0.032) when compared to the control group. In the control group the Student t-test (P<0.0006) showed a significantly different muscle behavior (Flexion>Extension Torque).. By using isokinetic assessment it was possible to quantify hypertonic spasticity in a group of subjects with spinal cord injury, distinguishing groups with higher and lower levels of spasticity as compared to a control group.

Topics: Adolescent; Adult; Analysis of Variance; Biomechanical Phenomena; Female; Humans; Knee Joint; Male; Muscle Spasticity; Spinal Cord Injuries; Torque

Pathologic fractures may occur with minimal trauma after spinal cord injury (SCI) because of osteoporosis. Rats were evaluated to determine whether they could be used as an SCI animal model. Male Sprague-Dawley rats underwent spinal cord transection at the ninth thoracic vertebrae. Control rats underwent a sham procedure. Mechanical testing of the humeral shaft, femoral shaft, tibial shaft, femoral neck, distal femur, and proximal tibia was performed separately at 0, 8, and 24 weeks after surgery. At 24 weeks, significant differences between SCI and control rats were found in maximum torque needed to produce failure in the femoral shaft (63 percent of control, p < 0.05) and tibial shaft (63 percent, p < 0.01), and in compressive load to produce failure in cross-sectional specimens of the distal femur (51 percent, p < 0.05) and proximal tibia (50 percent, p < 0.01). No differences were found in the maximum torque needed to produce failure of the humeral shaft (106 percent, p = 0.77) between SCI and control rats. Reductions in relative bone strength in SCI rats at 24 weeks were similar in magnitude to bone mineral density changes reported in humans with chronic paraplegia. Thus, Sprague-Dawley rats appear to be good animal models in which to evaluate changes in bone strength following SCI.

Topics: Animals; Bone Density; Disease Models, Animal; Male; Paraplegia; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries; Stress, Mechanical; Torque; Torsion Abnormality