vendex and Paraplegia

We hypothesize that the asynchronous low frequency stimulation of pads within multi-pad electrode will be less fatiguing compared to the conventional stimulation (two single pad electrodes) when generating comparable large forces of paralyzed human muscles. The experiments to verify the hypothesis were conducted on quadriceps of six individuals with chronic spinal cord injury (ASIA score A) who had not participated in any electrical stimulation program. The following stimulation protocols were compared: stimulation with a self adhesive 7 cm x 10 cm Pals Platinum cathode positioned over the top of the quadriceps (f = 40 Hz), and four oval 4 cm x 6 cm cathodes positioned over the proximal upper leg (f = 16 Hz). The anode in both cases was the 7 cm x 10 cm Pals Platinum electrode positioned over the distal part of the quadriceps. We measured the knee joint torque vs. time with a custom made apparatus, and estimated the interval before the knee joint torque decreased to 70% of the maximum. Mean fatigue interval increase for the four-pad stimulation protocol vs. single-pad stimulation protocol was 153.18%. This suggests that the use of multi-pad electrodes is favorable in cases where a prolonged stimulation of muscles is required.

Topics: Adult; Demography; Electric Stimulation; Electrodes; Humans; Knee Joint; Middle Aged; Muscle Fatigue; Paraplegia; Quadriceps Muscle; Surface Properties; Torque; 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

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

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

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

Paraplegic persons can stand with hip-knee-ankle-foot orthoses (HKAFO) and crutches. However, current HKAFOs restrict body movement extensively, which may impede functional upper-body movements. A more compliant body support using a more compliant orthosis or well-controlled functional electrical stimulation system may increase freedom of movement to the user, but should not impede stability and required arm support. In the current study, we investigated the consequences of varying stiffness applied at the hip to postural stability and required crutch force during paraplegic stance. Experiments were performed on five paraplegic persons with spinal cord lesions varying from T1 to T12. Static postures and dynamic responses to perturbations were tested for varying hip stiffness and crutch placements. The minimal hip-joint stiffness for stable stance appeared to depend on lesion level. In contrast to the predictions of a previous modeling study, no statistically significant influences of hip-joint stiffness or crutch-to-foot distance on posture and applied crutch forces were found. It is hypothesized that the main reasons of this discrepancy are the active upper-body efforts the paraplegic HKAFO users are still able to exert and the remaining flexibility of the upper trunk and shoulder region, which is present despite the restrictions of the orthosis.

Topics: Computer Simulation; Crutches; Elasticity; Equipment Failure Analysis; Feedback; Female; Hip Joint; Hip Prosthesis; Humans; Male; Models, Biological; Paraplegia; Postural Balance; Posture; Prosthesis Design; Stress, Mechanical; 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

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

Neuromuscular Electrical Stimulation (NMES) is commonly used in neuromuscular rehabilitation protocols, and its parameters selection substantially affects the characteristics of muscle activation. Here, we investigated the effects of short pulse width (200 µs) and higher intensity (short-high) NMES or long pulse width (1000 µs) and lower intensity (long-low) NMES on muscle mechanical output and fractional oxygen extraction. Muscle contractions were elicited with 100 Hz stimulation frequency, and the initial torque output was matched by adjusting stimulation intensity.. Fourteen able-bodied and six spinal cord-injured (SCI) individuals participated in the study. The NMES protocol (75 isometric contractions, 1-s on-3-s off) targeting the knee extensors was performed with long-low or short-high NMES applied over the midline between anterior superior iliac spine and patella protrusion in two different days. Muscle work was estimated by torque-time integral, contractile properties by rate of torque development and half-relaxation time, and vastus lateralis fractional oxygen extraction was assessed by Near-Infrared Spectroscopy (NIRS).. Torque-time integral elicited by the two NMES paradigms was similar throughout the stimulation protocol, with differences ranging between 1.4% (p = 0.877; able-bodied, mid-part of the protocol) and 9.9% (p = 0.147; SCI, mid-part of the protocol). Contractile properties were also comparable in the two NMES paradigms. However, long-low NMES resulted in higher fractional oxygen extraction in able-bodied (+ 36%; p = 0.006).. Long-low and short-high NMES recruited quadriceps femoris motor units that demonstrated similar contractile and fatigability properties. However, long-low NMES conceivably resulted in the preferential recruitment of vastus lateralis muscle fibers as detected by NIRS.

Topics: Electric Stimulation Therapy; Female; Humans; Leg; Male; Muscle Contraction; Oxygen Consumption; Paraplegia; Torque; Young Adult

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

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

For patients with lower limb paralysis, wearable robotic systems are becoming increasingly important for regaining mobility. The actuation of these systems is challenging because of the necessity to deliver high power within very limited space. However, not all patients need full support, as many patients have residual muscle function that can be applied for locomotion. This work introduces a microprocessor-controlled leg (hip-knee-ankle-foot) orthosis (mpLeg) with energy recuperation capabilities at the hip joint. The system redistributes motion energy generated by the patient during walking. In stance phase of walking, energy is stored in an elastic element at the hip joint. This energy can be released by computer control later in the gait phase, to support swing phase motion. This work aims at investigating the influence of the elastic element in the orthotic hip joint on a patient's motion. Experiments conducted with a patient suffering from incomplete paraplegia demonstrated that the motion pattern during walking improved with activated energy recuperation. This observation was made over a wide range of system parameters. The patient used the energy recuperation capabilities of the mpLeg with up to 4.1 J recuperated energy per step, which resulted in a more natural swing phase motion during walking. Therefore energy recuperation at the hip joint is a feasible technology for future supportive devices.

Topics: Female; Hip Joint; Humans; Knee; Middle Aged; Orthotic Devices; Paraplegia; Torque; Walking

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

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

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

This paper describes the application of a powered lower limb exoskeleton to aid paraplegic individuals in stair ascent and descent. A brief description of the exoskeleton hardware is provided along with an explanation of the control methodology implemented to allow stair ascent and descent. Tests were performed with a paraplegic individual (T10 complete injury level) and data is presented from multiple trials, including the hip and knee joint torque and power required to perform this functionality. Joint torque and power requirements are summarized, including peak hip and knee joint torque requirements of 0.75 Nm/kg and 0.87 Nm/kg, respectively, and peak hip and knee joint power requirements of approximately 0.65 W/kg and 0.85 W/kg, respectively.

Topics: Body Weight; Evaluation Studies as Topic; Humans; Lower Extremity; Male; Orthotic Devices; Paraplegia; Posture; Torque; Walking

We present a low-frequency stimulation method via multi-pad electrodes for delaying muscle fatigue. We compared two protocols for muscle activation of the quadriceps in paraplegics. One protocol involved a large cathode at 30 HZ (HPR, high pulse-rate), and the other involved four smaller cathodes at 16 HZ (LPR, low pulse-rate). The treatment included 30-min daily sessions for 20 days. One leg was treated with the HPR protocol and the other with the LPR protocol. Knee-joint torque was measured before and after therapy to assess the time interval before the knee-joint torque decreased to 70% of the initial value. The HPR therapy provided greater increases in muscle endurance and force in prolonged training. Yet the LPR stimulation produced less muscle fatigue compared to the HPR stimulation. The results suggest that HPR is the favored protocol for training, and LPR is better suited for prolonged stimulation.

Topics: Adult; Electric Stimulation; Electrodes; Equipment Design; Female; Humans; Knee Joint; Male; Middle Aged; Muscle Fatigue; Paraplegia; Physical Endurance; Quadriceps Muscle; Quadriplegia; Torque; 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

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

Cross-sectional study.. To evaluate isokinetic shoulder flexor-extensor (F/E) and abductor-adductor (Ab/Ad) torque ratios in individuals with paraplegia using a new interpretative approach. We proposed to study torque ratios according to joint angle sections (15 degrees angle subgroups) over a selected range of motion.. Pathokinesiology Laboratory, Montreal, Canada.. Sixteen individuals with complete motor paraplegia, without shoulder pain or impairment, were included in this study. After a preloading period of 1 s, maximum isokinetic concentric contractions of all muscle groups were completed at 30, 60 and 120 degrees s(-1) over the entire tested ranges of motion (70 to -35 degrees for the flexion-extension and 15 to 60 degrees for the abduction-adduction). After the continuous torque curves were rebuilt, the mean F/E and Ab/Ad torque ratios were calculated and analyzed every 15 degrees.. A significant modification of the F/E (F=66.3; P<0.001) and Ab/Ad (F=100.6; P<0.001) torque ratios was observed according to the 15 degrees angle subgroup evaluated. More precisely, a progressive decline of both the F/E and Ab/Ad ratios was noted as the shoulder flexion or abduction progressed. Angular velocity did not have any influence on torque ratio values.. Angle subgroup torque ratio analysis leads to a better estimation of the balance between the agonist and antagonist muscle groups than does traditional peak torque ratio analysis. In individuals with paraplegia, this precise estimation of torque ratios may lead to the development of specific shoulder strengthening programs to prevent muscle imbalance and its consequences.

Topics: Adult; Chi-Square Distribution; Cross-Sectional Studies; Evaluation Studies as Topic; Humans; Isometric Contraction; Isotonic Contraction; Male; Middle Aged; Muscle Strength Dynamometer; Musculoskeletal Physiological Phenomena; Outcome Assessment, Health Care; Paraplegia; Range of Motion, Articular; Shoulder; Torque

Arm-free paraplegic standing via functional electrical stimulation (FES) has drawn much attention in the biomechanical field as it might allow a paraplegic to stand and simultaneously use both arms to perform daily activities. However, current FES systems for standing require that the individual actively regulates balance using one or both arms, thus limiting the practical use of these systems. The purpose of the present study was to show that actuating only six out of 12 degrees of freedom (12-DOFs) in the lower limbs to allow paraplegics to stand freely is theoretically feasible with respect to multibody stability and physiological torque limitations of the lower limb DOF. Specifically, the goal was to determine the optimal combination of the minimum DOF that can be realistically actuated using FES while ensuring stability and able-bodied kinematics during perturbed arm-free standing. The human body was represented by a three-dimensional dynamics model with 12-DOFs in the lower limbs. Nakamura's method (Nakamura, Y., and Ghodoussi, U., 1989, "Dynamics Computation of Closed-Link Robot Mechanisms With Nonredundant and Redundant Actuators," IEEE Trans. Rob. Autom., 5(3), pp. 294-302) was applied to estimate the joint torques of the system using experimental motion data from four healthy subjects. The torques were estimated by applying our previous finding that only 6 (6-DOFs) out of 12-DOFs in the lower limbs need to be actuated to facilitate stable standing. Furthermore, it was shown that six cases of 6-DOFs exist, which facilitate stable standing. In order to characterize each of these cases in terms of the torque generation patterns and to identify a potential optimal 6-DOF combination, the joint torques during perturbations in eight different directions were estimated for all six cases of 6-DOFs. The results suggest that the actuation of both ankle flexionextension, both knee flexionextension, one hip flexionextension, and one hip abductionadduction DOF will result in the minimum torque requirements to regulate balance during perturbed standing. To facilitate unsupported FES-assisted standing, it is sufficient to actuate only 6-DOFs. An optimal combination of 6-DOFs exists, for which this system can generate able-bodied kinematics while requiring lower limb joint torques that are producible using contemporary FES technology. These findings suggest that FES-assisted arm-free standing of paraplegics is theoretically feasible, even when limited by the fac

Topics: Arm; Computer Simulation; Electric Stimulation Therapy; Gait; Humans; Lower Extremity; Models, Biological; Movement; Nonlinear Dynamics; Paraplegia; Postural Balance; Posture; Range of Motion, Articular; Self-Help Devices; Torque

The pendulum test was applied to evaluate functional electrical stimulation (FES)-induced joint moments in paraplegics with denervated muscles. Therefore a manipulandum was connected to the knee joint and programmed to elicit gravity-induced leg oscillations. The FES-induced output torque was compensated for in order to keep the leg in a mean vertical position (knee angle 90 degrees ). A second-order dynamical model was applied to extract the elastic and viscous moments from the recorded leg oscillations. This model provided an almost adequate description of the relaxed and FES-contracted states. In the relaxed state the elastic moment was 15.3 +/- 2.37 Nm/rad and the viscous moment was 0.41 +/- 0.21 Nms/rad. The FES-induced elastic moment was 29.4 +/- 28.5 Nm/rad and the FES-induced viscous moment was 1.53 +/- 1.03 Nms/rad (N = 10, before FES-training).

Topics: Adult; Biomechanical Phenomena; Electric Stimulation Therapy; Female; Humans; Knee Joint; Male; Middle Aged; Muscle Contraction; Muscle Denervation; Muscle, Skeletal; Paraplegia; Torque; Treatment Outcome

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

During fixed-ankle FES cycling in paraplegics, in which the leg position is completely determined by the crank angle, mechanical power output is low. This low power output limits the cardiovascular load that could be realized during FES ergometer cycling, and limits possibilities for FES cycling as a means of locomotion. Stimulation of ankle musculature in a released-ankle setup might increase power output. However, releasing the ankle joint introduces a degree of freedom in the leg that has to be controlled, which imposes constraints on the stimulation pattern.. In this study, a forward dynamics modeling/simulation approach was used to assess the potential effect of releasing the ankle on the maximal mechanical power output.. For the released-ankle setup, the optimal stimulation pattern was found to be less tightly related to muscle shortening/lengthening than for the fixed-ankle setup, which indicates the importance of the constraints introduced by releasing the ankle. As a result, the maximal power output for 45-RPM cycling in the released-ankle setup was found to be about 10% lower than with a fixed ankle, despite the additional muscle mass available for stimulation. Power output for the released-ankle setup can be improved by tuning the point of contact between the foot and pedal to the relative strength of the ankle plantar flexors. For the model used, power output was 14% higher than for the fixed-ankle setup when this point of contact was moved posteriorly by 0.075 m.. Releasing the ankle joint and stimulating the triceps surae and tibialis anterior is expected to result in a modest increase in power output at best.

Topics: Acceleration; Ankle Joint; Biomechanical Phenomena; Electric Stimulation; Exercise Test; Humans; Immobilization; Isometric Contraction; Models, Biological; Muscle, Skeletal; Paraplegia; Torque

In the past, limited unsupported standing has been restored in patients with thoracic spinal cord injury through open-loop functional electrical stimulation of paralyzed knee extensor muscles and the support of intact arm musculature. Here an optimal control system for paralyzed ankle muscles was designed that enables the subject to stand without hand support in a sagittal plane. The paraplegic subject was conceptualized as an underactuated double inverted pendulum structure with an active degree of freedom in the upper trunk and a passive degree of freedom in the paralyzed ankle joints. Control system design is based on the minimization of a cost function that estimates the effort of ankle joint muscles via observation of the ground reaction force position, relative to ankle joint axis. Furthermore, such a control system integrates voluntary upper trunk activity and artificial control of ankle joint muscles, resulting in a robust standing posture. Figures are shown for the initial simulation study, followed by disturbance tests on an intact volunteer and several laboratory trials with a paraplegic person. Benefits of the presented methodology are prolonged standing sessions and in the fact that the subject is able to maintain voluntary control over upper body orientation in space, enabling simple functional standing.

Topics: Algorithms; Ankle; Computer Simulation; Feedback; Humans; Models, Biological; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Paraplegia; Postural Balance; Posture; Stress, Physiological; Torque

The prerequisites for stable crutch supported standing were analyzed in this paper. For this purpose, a biomechanical model of crutch supported paraplegic stance was developed assuming the patient was standing with extended knees. When using crutches during stance, the crutches will put a position constraint on the shoulder, thus reducing the number of degrees of freedom. Additional hip-joint stiffness was applied to stabilize the hip joint and, therefore, to stabilize stance. The required hip-joint stiffness for changing crutch placement and hip-joint offset angle was studied under static and dynamic conditions. Modeling results indicate that, by using additional hip-joint stiffness, stable crutch supported paraplegic standing can be achieved, both under static as well as dynamic situations. The static equilibrium postures and the stability under perturbations were calculated to be dependent on crutch placement and stiffness applied. However, postures in which the hip joint was in extension (C postures) appeared to the most stable postures. Applying at least 60 N x m/rad hip-joint stiffness gave stable equilibrium postures in all cases. Choosing appropriate hip-joint offset angles, the static equilibrium postures changed to more erect postures, without causing instability or excessive arm forces to occur.

Topics: Computer Simulation; Crutches; Elasticity; Equipment Failure Analysis; Feedback; Hip Joint; Hip Prosthesis; Humans; Models, Biological; Paraplegia; Postural Balance; Posture; Prosthesis Design; Torque

To study maximal upper-extremity torque values and agonist/antagonist torque ratios in a sample of individuals with paraplegia and to compare these values with a sample of age-, gender-, and weight-matched able-bodied individuals.. Cross-sectional, case-control study.. A biomechanics laboratory.. A convenience sample of 15 men with complete (American Spinal Injury Association class A) T5-L2 paraplegia and 15 able-bodied control subjects.. Not applicable.. Maximal isometric torques of 12 upper-extremity muscle groups (shoulder, elbow, and wrist flexion and extension; shoulder abduction and adduction; shoulder internal and external rotation; elbow pronation and supination) were measured with custom dynamometers.. Maximal torque values and agonist/antagonist torque ratios for the shoulder, elbow, and wrist functions did not differ between the control subjects and those with complete paraplegia, with the exception of the supination/pronation torque ratio, which was significantly higher in the able-bodied control group.. Wheelchair propulsion and other functional activities, such as transfers, do not significantly affect maximum torque production of the upper extremities in individuals with paraplegia. On the basis of these findings, arguments that upper-extremity muscle imbalances are important contributory factors to upper-extremity pain and dysfunction in this group may be too simplistic.

Topics: Adult; Arm; Case-Control Studies; Cross-Sectional Studies; Humans; Isometric Contraction; Locomotion; Male; Middle Aged; Paraplegia; Physical Exertion; Range of Motion, Articular; Torque; Wheelchairs

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

The effects of spinal cord injury level on shoulder kinetics during manual wheelchair propulsion were studied.. Single session data collection in a laboratory environment.. Male subjects were divided into four groups: low level paraplegia (n=17), high level paraplegia (n=19), C7 tetraplegia (C7, n=16) and C6 tetraplegia (C6, n=17). Measurements were recorded using a six-camera VICON motion analysis system, a strain gauge instrumented wheel, and wheelchair ergometer. Shoulder joint forces and moments were calculated using the inverse dynamics approach.. Mean self-selected propulsion velocity was higher in the paraplegic (low paraplegia=90.7 m/min; high paraplegia=83.4 m/min) than tetraplegic (C7=66.5 m/min; C6=47.0 m/min) groups. After covarying for velocity, no significant differences in shoulder joint moments were identified. However, superior push force in subjects with tetraplegia (C7=21.4 N; C6=9.3 N) was significantly higher than in those with high paraplegia (7.3 N), after covarying velocity.. The superior push force in the tetraplegic groups coupled with weakness of thoraco-humeral depressors increases susceptibility of the subacromial structures to compression.. Increased vertical force at the shoulder joint, coupled with reduced shoulder depressor strength, may contribute to shoulder problems in subjects with tetraplegia. Wheelchair design modifications, combined with strength and endurance retention, should be considered to prevent shoulder pain development.

Topics: Adult; Analysis of Variance; Arm; Biomechanical Phenomena; Ergometry; Humans; Male; Paraplegia; Physical Exertion; Quadriplegia; Shoulder Joint; Torque; Wheelchairs

The knowledge of the behavior of electrically activated muscles is an important requisite for the development of functional electrical stimulation (FES) systems to restore mobility to persons with paralysis. The aim of this work was to develop a model capable of relating electrical parameters to dynamic joint torque for FES applications. The knee extensor muscles, stimulated using surface electrodes, were used for the experimental preparation. Both healthy subjects and people with paraplegia were tested. The dynamics of the lower limb were represented by a nonlinear second order model, which took account of the gravitational and inertial characteristics of the anatomical segments as well as the damping and stiffness properties of the knee joint. The viscous-elastic parameters of the system were identified experimentally through free pendular movements of the leg. Leg movements induced by quadriceps stimulation were acquired too, using a motion analysis system. Results showed that, for the considered experimental conditions, a simple one-pole transfer function is able to model the relationship between stimulus pulsewidth (PW) and active muscle torque. The time constant of the pole was found to depend on the stimulus pattern (ramp or step) while gain was directly dependent on stimulation frequency.

Topics: Bias; Case-Control Studies; Elasticity; Electric Stimulation Therapy; Gravitation; Humans; Knee Joint; Leg; Male; Models, Biological; Muscle Contraction; Nonlinear Dynamics; Paraplegia; Range of Motion, Articular; Time Factors; Torque; Viscosity

This work establishes a method for the noninvasive in vivo identification of parametric models of electrically stimulated muscle in paralyzed individuals, when significant inertial loads and/or load transitions are present. The method used differs from earlier work, in that both the pulse width and stimulus period (interpulse interval) modulation are considered. A Hill-type time series model, in which the output is the product of two factors (activation and torque-angle) is used. In this coupled model, the activation dynamics depend upon velocity. Sequential nonlinear least squares methods are used in the parameter identification. The ability of the model, using identified time-varying parameters, to accurately predict muscle torque outputs is evaluated, along with the variability of the identified parameters. This technique can be used to determine muscle parameter models for biomechanical computer simulations, and for real-time adaptive control and monitoring of muscle response variations such as fatigue.

Topics: Algorithms; Biomechanical Phenomena; Electric Stimulation; Female; Humans; Leg; Linear Models; Male; Muscle Contraction; Muscle, Skeletal; Paraplegia; Signal Processing, Computer-Assisted; Torque

The sit-to-stand transfer of paraplegic patients using functional electrical stimulation (FES) of the knee extensors and arm support was analyzed in the study. In a group of 8 completely paralyzed subjects who were trained FES users, kinematic and dynamic parameters were recorded during standing up trials. A contactless optical system was used to assess the human body motion. The forces acting on the human body were measured by multi-axis force transducers. On the basis of recursive Newton-Euler inverse dynamic analysis, the forces and torques acting on the body joints were calculated. The joint moments in the lower and upper extremities during the sit-to stand task are presented in this paper. The influences of the patient's strength, FES training duration, and rising strategy on the joint loading are discussed.

Topics: Adult; Ankle Joint; Arm; Electric Stimulation Therapy; Female; Hip Joint; Humans; Knee Joint; Lumbar Vertebrae; Male; Middle Aged; Movement; Muscle Contraction; Muscle, Skeletal; Paraplegia; Posture; Sacrum; Shoulder Joint; Stress, Mechanical; Torque; Transducers; Weight-Bearing

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

Prolonged immobilization, such as occurs after the spinal cord injury (SCI), results in several physiological problems. It has been demonstrated that the standing posture can ameliorate many of these problems. Standing exercise can be efficiently performed by the help of functional electrical stimulation (FES). The first application of FES to a paraplegic patient was reported by Kantrowitz in 1963. It was later shown by our group that standing for therapeutic purposes can be achieved by a minimum of two channels of FES delivered to both knee extensors. The properties of the stimulated knee extensors (maximal isometric joint torque, fatiguing, and spasticity) were not found as sufficient conditions for efficient standing exercise. According to our studies, the ankle joint torque during standing is the only parameter which is well correlated to the duration of FES assisted standing. For good standing low values of the ankle joint torque are required. To minimize the ankle joint torque the lever belonging to the vertical reaction force must be decreased. Adequate alignment of the posture appears to be the prerequisite for efficient FES assisted and arm supported standing exercise. Some patients are able to assume such posture by themselves, while many must be aided by additional measures. At present, surface stimulation of knee extensors combined with some appropriately "compliant shoes" looks to be adequate choice.

Topics: Ankle Joint; Biomechanical Phenomena; Electric Stimulation Therapy; Exercise Therapy; Gravitation; Humans; Knee Joint; Paraplegia; Posture; Range of Motion, Articular; Torque; Treatment Outcome

To develop an effective selection procedure for lower limb functional neurostimulation (LLFNS) for standing in paraplegia.. The selection procedure and exclusion criteria were based on the previous experience for two clinical centres with experience of LLFNS.. Two Regional Spinal Injuries units in southern England.. 254 fully rehabilitated paraplegics living in the community.. Patients were invited to participate in the programme, and if suitable to subject themselves to a rigorous staged selection procedure from which they could withdraw at any time.. Functionally successful home standing using closed-loop surface electrical stimulation.. 57/254 patients were suitable on paper and were accessible. 19 of these (CI = 10-28) were interested in the project and attended one of the spinal centres for details. Twelve (CI = 5-19) of these fulfilled the selection criteria and started on the training programme; and 10 of them completed the muscle training programme successfully. Seven patients (CI = 2-12) achieved closed-loop standing in the laboratory and four patients (CI = 1-8) did so at home.

Topics: Adult; Anxiety; Bone Density; Depression; Electric Stimulation Therapy; Female; Humans; Leg; Male; Middle Aged; Muscle Spasticity; Muscles; Paraplegia; Patient-Centered Care; Personnel Selection; Physical Endurance; Prostheses and Implants; Regional Blood Flow; Torque

Shoulder complaints are frequently observed to result from the increased stress to the upper extremities of wheelchair users. The cause may be muscle dysbalances of the stressed musculature, whereby the changed situation in the wheelchair during everyday and athletic exercise is important. To demonstrate the different importance of altered shoulder stress in the wheelchair situation and in additional athletic stress, maximum strength in the dominant shoulder was recorded in 14 trained and 13 untrained paraplegics. The goal was to examine the differences between the groups during concentric (60 degrees/s) and eccentric (60 degrees/s) shoulder exercise. Based on the strength/velocity curve, differentiation was also made between the shoulder movements in dependence on various movement velocities. Finally, a comparison was to be made with the test results of untrained and trained, non-paralyzed subjects examined by the same test methods in earlier studies. The results show higher maximum torques in both groups under eccentric stress (p < 0.001), more expressed in trained paraplegics (p < 0.001). In group comparison, there are only slight differences in concentric exercise. The comparison between untrained paraplegics and untrained normal persons (non-paralyzed) show hardly any differences. Trained paraplegics attain values comparable to those of non-paralyzed athletes in eccentric and isometric shoulder exercise. It is concluded, that objective data for determination of the strength situation in the shoulder musculature can be obtained by isokinetic strength measurements in paraplegics. Obviously, eccentric forms of exercise are particularly important. Valuable information can be obtained by determining shoulder strength in dependence on work mode and comparison with non-paralyzed subjects; the information must be interpreted according to the movement.

Topics: Adult; Humans; Isometric Contraction; Male; Middle Aged; Paraplegia; Physical Education and Training; Range of Motion, Articular; Reference Values; Shoulder; Sports; Torque; Wheelchairs

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

We recorded in 15 complete paraplegic patients the torque output and the surface action potentials (SAP) produced by the electrically stimulated quadriceps muscle during an isometric contraction lasting 126 s. We studied the evolution during the test of the peak to peak amplitude, the latency from the onset of stimulation, the rising time to peak, the peak to peak duration, the area of the recorded SAPs and we tried to relate those data to the torque production. Results were extremely different among patients but the general behaviour facing this test was comparable. After a short increase the mechanical output decreased and reached a plateau (range from 7.13 to 53.5% of initial value). The peak to peak amplitude first increased and then decreased, and was not related to the torque production. The latency, the rising time to peak and the peak to peak duration continuously increased to a maximum and then plateaued or slightly decreased after different courses of time. The latency from the onset of stimulation was less affected by the test than the rising time to peak and the peak to peak duration. Therefore, the nerve conduction velocity and the neuromuscular junction transmission did not vary to a great extent compared to the muscle fibre conduction velocity. The area of the rectified SAPs first increased and then decreased and was not related to the torque decrease.

Topics: Action Potentials; Electric Stimulation; Humans; Isometric Contraction; Muscle, Skeletal; Neural Conduction; Paraplegia; Reaction Time; Signal Processing, Computer-Assisted; Software; Surface Properties; Torque

This study presents a mathematical model by which power output (PO) delivered to the rear wheel during handrim wheelchair propulsion on a roller ergometer can be determined for individual wheelchair-user combinations. PO is calculated from the torque applied to the wheel and its angular velocity. The torque applied is a function of one total internal torque of the wheelchair-ergometer system, the rotational moment of inertia of the rear wheel, the one of the roller and its angular acceleration. The total internal torque reflects all internal friction forces and is determined with a deceleration test. To assess the reliability of this approach, 11 able-bodied subjects underwent progressively increasing exercise tests on two different occasions. PO values ranged from 12 to 63 W and were highly reliable (r2 > 0.95). Peak physiological responses were never different from test 1 and 2 (repeated measures ANOVA; p: N.S.) and correlations were 0.90, 0.72, 0.88, 0.82, 0.70 and 0.85 for PO, oxygen uptake (VO2), heart rate, minute ventilation, carbon dioxide production and blood lactate concentration, respectively. After an initial increase, gross mechanical efficiency dropped at higher velocities, with values ranging from 4.64 to 11.26%. In conclusion, the roller ergometer, the mathematical model to determine PO and the protocol used seem to be adequate to exercise test people in a handrim wheelchair. It is feasible to apply the theoretical procedure to other roller ergometers which would allow for comparisons of exercise intensities and protocols between different devices used in exercise physiology and rehabilitation.

Topics: Adult; Analysis of Variance; Ergometry; Heart Rate; Humans; Male; Models, Theoretical; Oxygen Consumption; Paraplegia; Physical Exertion; Reproducibility of Results; Torque; Wheelchairs