vendex and Muscle-Weakness

Strength deficits may play a central role in the severity of balance, mobility, and endurance impairments in lower limb prosthesis users. A body of literature detailing the scope and specifics of muscle weakness in lower limb prosthesis users is emerging, but has yet to be summarized. A synopsis of strength deficits, and their impact on functional abilities in lower limb prosthesis users, may inform rehabilitation and research needs.. Synthesize reported strength deficits in lower limb prosthesis users, and discuss possible causes, consequences, and solutions.. Scoping review.. A search of biomedical databases was performed, and inclusion/exclusion criteria were applied to identify publications relevant to the purpose of the review.. In all, 377 publications were identified, of which 12 met the inclusion/exclusion criteria. When compared with the controls and the intact limb, the primary strength outcome, peak torque, was lower in transtibial residual limb knee flexors and extensors, as well as transfemoral residual limb hip muscles.. The reviewed studies provide evidence of strength deficits in lower limb prosthesis users. These deficits appear to be consequential, as they may contribute to balance, mobility, and endurance impairments. Additional research exploring alternative strength metrics, clinical tests, and causal links to functional impairments is required.. Evidence of muscle weakness among lower limb prosthesis users, and its influence on balance, mobility, and endurance, suggests that greater clinical attention and scientific inquiry into physical conditioning of lower limb prosthesis users is merited and required.

Topics: Amputees; Artificial Limbs; Humans; Lower Extremity; Muscle Weakness; Torque

Hamstring strain injuries are amongst the most common and problematic injuries in a wide range of sports that involve high speed running. The comparatively high rate of hamstring injury recurrence is arguably the most concerning aspect of these injuries. A number of modifiable and nonmodifiable risk factors are proposed to predispose athletes to hamstring strains. Potentially, the persistence of risk factors and the development of maladaptations following injury may explain injury recurrence. Here, the role of neuromuscular inhibition following injury is discussed as a potential mechanism for several maladaptations associated with hamstring re-injury. These maladaptations include eccentric hamstring weakness, selective hamstring atrophy and shifts in the knee flexor torque-joint angle relationship. Current evidence indicates that athletes return to competition after hamstring injury having developed maladaptations that predispose them to further injury. When rehabilitating athletes to return to competition following hamstring strain injury, the role of neuromuscular inhibition in re-injury should be considered.

Topics: Athletic Injuries; Cicatrix; Humans; Knee Joint; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Neural Inhibition; Recurrence; Risk Factors; Sprains and Strains; Torque

Age-related losses in lower extremity strength result in functional disabilities that diminish the quality of life for many older adults. Multiple factors, including type of muscle fiber, size of the muscle, length and speed of the muscle at contraction, age, and gender, affect the magnitude of strength generated. Assessment in clinical practice, in order to be cost and time effective, screens older adults for loss in strength. Further evaluation of strength loss requires the use of sophisticated procedures and equipment. Research into the causes of loss of strength and interventions to lessen or prevent loss of strength requires valid and reliable assessment tools. This article examines components of isokinetic muscle strength, the measurement of strength in clinical practice, methods to measure isokinetic strength, and validity and reliability of these measures.

Topics: Adult; Age Factors; Aged; Female; Humans; Isotonic Contraction; Male; Mass Screening; Middle Aged; Muscle Weakness; Nursing Research; Physical Examination; Range of Motion, Articular; Reference Values; Reproducibility of Results; Research Design; Risk Factors; Severity of Illness Index; Sex Characteristics; Torque

Wong, V, Dankel, SJ, Spitz, RW, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. The effect of blood flow restriction therapy on recovery after experimentally induced muscle weakness and pain. J Strength Cond Res 36(4): 1147-1152, 2022-The purpose was to determine if blood flow restriction with no external load could be used as a means of active therapy after experimentally induced fatigue and soreness. Twelve women and 7 men (aged 18-35 years) participated in a randomized controlled trial using a within-subject design. The study intervention was 3 consecutive visits. Visit 1 included the fatiguing/soreness-inducing protocol for the elbow flexors, which was performed only once during the study. Torque was measured before/after to confirm individuals began in a weakened state. Subjects then completed blood flow restriction therapy on one arm and the sham therapy on the other. Subjects performed elbow flexion/contraction with no external load on both arms. Torque was measured once more 10 minutes after the fatiguing/soreness-inducing protocol. Twenty-four hours later, soreness and torque were assessed in each arm, followed by another bout of therapy. Forty-eight hours after the initial visit, soreness and torque were measured again. There were no differences (median difference [95% credible interval]) in the recovery of torque between the blood flow restriction and sham therapy conditions at 10 minutes (0.5 [-2.7, 3.8] N·m), 24 hours (-2.34 [-6, 1.14] N·m), or 48 hours (-1.94 [-5.45, 1.33] N·m). There were also no differences in ratings of soreness at 24 hours (-2.48 [-10.05, 5.05]) or 48 hours (2.58 [-4.96, 10.09]). Our results indicate that this specific model of blood flow restriction therapy did not enhance the recovery of the muscle compared with a sham condition without the application of pressure.

Topics: Adolescent; Adult; Blood Flow Restriction Therapy; Exercise; Female; Humans; Male; Muscle Weakness; Muscle, Skeletal; Pain; Torque; Young Adult

Neuromuscular electrical stimulation (NMES) is a viable intervention for improving impaired muscle function in individuals with rheumatoid arthritis (RA). However, there is limited evidence about the dose-response relationship between NMES and muscle function in these individuals.. The objectives of this study were to investigate the dose-response relationship between NMES and muscle function in individuals with RA and to establish the minimal NMES training intensity for promoting improvements.. This study was a secondary analysis of data obtained before and after an NMES intervention in a randomized study.. The study took place at a research clinic. Only adults diagnosed with RA were included. The intervention consisted of 36 NMES treatment sessions for the quadriceps muscles over 16 weeks. Muscle function was measured before and after the intervention; quadriceps cross-sectional area and muscle quality were assessed using computed tomography, and strength was measured with an isokinetic dynamometer. NMES training intensity was calculated as a percentage by dividing NMES-elicited quadriceps muscle torque by the maximum voluntary isometric contraction. Improvements in muscle function were calculated using paired-sample t tests. The dose-response relationship was determined using curve estimation regression statistics. The minimum NMES training intensity was defined as that sufficient to significantly improve all muscle function measures.. Twenty-four people (48 legs) participated (75% women; mean [SD] age = 58 [8] years; mean body mass index = 32 [7] kg/m2). Quadriceps cross-sectional area, muscle quality, and strength improved after the intervention. Associations between NMES training intensity and muscle quality (r2 = 0.20) and strength (r2 = 0.23) were statistically significant, but that between NMES training intensity and muscle cross-sectional area was not (r2 = 0.02). The minimum NMES training intensity necessary to improve all measures of muscle function ranged from 11% to 20% of the maximum voluntary isometric contraction.. The relatively small sample size was a limitation.. The minimum NMES training intensity for significant gains in muscle function was ∼15%. Higher NMES intensities may promote better muscle quality and strength in individuals with RA.

Topics: Arthritis, Rheumatoid; Body Mass Index; Electric Stimulation Therapy; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Quadriceps Muscle; Regression Analysis; Sample Size; Torque

This study examined the effects of passive stretching only (PS+CON) and passive stretching with the addition of continuous vibration (VIB) during post-passive stretching tests (PS+VIB) on peak torque (PT), percent voluntary inactivation (%VI), single stimulus twitch torque (TTSINGLE), and doublet stimuli twitch torque (TTDOUBLET) of the plantar flexors at a short (20° plantar flexion (PF)) and long muscle length (15° dorsiflexion (DF)). Fourteen healthy men (age = 22 ± 3 years) performed isometric maximal voluntary contractions at PF and DF, and passive range of motion (PROM) assessments before and after 8 × 30-s passive stretches without (PS+CON) or with VIB (PS+VIB) administered continuously throughout post-passive stretching tests. The passive properties of the muscle tendon unit were assessed pre- and post-passive stretching via PROM, passive torque (PASSTQ), and musculotendinous stiffness (MTS) measurements. PT, TTSINGLE, and TTDOUBLET decreased, whereas, %VI increased following passive stretching at PF and DF (P < 0.05) with no significant differences between PS+CON and PS+VIB. PASSTQ and MTS decreased while PROM increased post-passive stretching during both trials (P < 0.05). The stretching-induced force/torque deficit and increases in %VI were evident following passive stretching at short and long muscle lengths. Although not statistically significant, effect size calculations suggested large and moderate differences in the absolute changes in PT (Cohen's d = 1.14) and %VI (Cohen's d = 0.54) from pre- to post-passive stretching between treatments, with PS+VIB having greater decreases of PT and higher %VI than PS+CON. The decrement in PT following passive stretching may be primarily neural in origin.

Topics: Achilles Tendon; Adult; Evoked Potentials, Motor; Humans; Isometric Contraction; Male; Muscle Strength; Muscle Stretching Exercises; Muscle Weakness; Muscle, Skeletal; Plantar Plate; Range of Motion, Articular; Severity of Illness Index; Torque; Transcutaneous Electric Nerve Stimulation; Vibration; Young Adult

Few examined the contribution of neural and muscular deficits to weakness in the same stroke subject. We determined maximal voluntary contraction (MVC) and 50 Hz torques, activation (twitch interpolation), electromyographic (EMG) amplitude and antagonist coactivation, and muscle volume using magnetic resonance imaging (MRI) of the dorsiflexors bilaterally in 7 chronic stroke subjects (40-67 y). Recordings of MVC and 50 Hz torque were also done in 7 control subjects (24-69 y) without stroke. The MVC torque was smaller in the contralesional than ipsilesilesional limb (29.8 ± 21.3 Nm vs. 42.5 ± 12.0 Nm, p = .04), and was associated with deficits in activation (r2 = .77) and EMG amplitude (r2 = .71). Antagonist coactivation percentage was not significantly different between limbs. Muscle volume, 50 Hz torque, and specific torque (50Hz torque/muscle volume) were also not different between sides. The concept that atrophy is commonplace after stroke is not supported by the results. Our findings indicate that dorsiflexor weakness in mobile stroke survivors is not explained by atrophy or reduced torque generating capacity suggesting an important role for central factors.

Topics: Adult; Aged; Case-Control Studies; Chronic Disease; Electric Stimulation; Electromyography; Evoked Potentials, Motor; Female; Gait; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Stroke; Survivors; Torque; Walking

To investigate the effects of eight weeks whole body vibration training program on leg muscle strength (force-producing capacity) in adults after healed burns.. Randomized controlled trial.. Faculty of Physical Therapy, Cairo University.. Thirty-one burned patients participated in the study and were randomized into whole body vibration group and control group. Non-burned healthy adults were assessed similarly to burned subjects and served as matched healthy controls.. The whole body vibration group performed an eight weeks vibration program three times a week on a vibration platform; the control group received home based physical therapy program without vibration training.. Assessment of knee extensors and ankle planter flexor strength by isokinetic dynamometer at 150°/s were performed at the beginning of the study and at the end of the training period for both groups.. Subjects with burns more than 36% TBSA produced significantly less torque in the quadriceps and calf muscle than non-burned healthy subjects. Patients in whole body vibration group showed a significant improvement in knee extensor and ankle planter flexor strength as compared with those in the control group. Knee extensor strength and percent improvement was 233.40±5.74 (64.93±3.03 change score) and 38.54% for the vibration group and 190.07±3.99 (21.66±4.41 change score) and 12.86% for the control group, ankle plantar flexor strength and percent improvement was 156.27±5.95 (54.53±6.16 change score) and 53.70% for the vibration group and 116.13±3.24 (14.66±2.71 change score) and 14.52% for the control group.. Participation in whole body vibration program resulted in a greater improvement in quadriceps and calf muscle strength in adults with healed thermal burn compared to base line values; a WBV program is an effective for strength gain in rehabilitation of burned patients.

Topics: Adult; Burns; Female; Humans; Leg; Male; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Quadriceps Muscle; Torque; Vibration

Due to its influence on haemophilic arthropathy, the evaluation of knee extensor (K(Ext)) and flexor (K(Flex)) torques plays an important role in the preventive and rehabilitative context of haemophilia. Thus, the present study aimed at investigating maximal static torque (M(Max)) of K(Ext) and K(Flex). 14 boys with haemophilia (8 severe, 6 moderate; age: 11.7 ± 2.8 years; prophylactic treatment > 5 years) and 14 healthy carefully pair-matched controls (age: 11.5 ± 2.7 years) were separately measured for the left and right leg for M(Max). Furthermore, the ratio K(Flex)/K(Ext )was calculated and the joint situation assessed using the Haemophilia Joint Health Score.. No significant group-effect was observed for M(Max) of the K(Ext) and K(Flex) as well as for the ratio K(Flex)/K(Ext) (p>0.05). Despite significant higher joint scores in haemophilic children compared to their healthy controls (p<0.01), patients merely showed minor joint impairments.. Children and adolescents with severe and moderate haemophilia under prophylactic replacement treatment with a good joint status showed comparable maximal strength performance of relevant knee muscles compared to their healthy peers.

Topics: Adolescent; Blood Coagulation Factors; Child; Female; Hemophilia A; Humans; Knee Joint; Male; Muscle Strength; Muscle Weakness; Torque; Treatment Outcome; Young Adult

Repetitive blood flow restriction prevents muscular atrophy and weakness induced by chronic unloading. However, it was unclear which external compressive force for blood flow restriction was optimal to prevent muscular dysfunction. The present study was intended to investigate the effects of repeated muscle blood flow restriction at low pressure on muscular weakness induced by immobilization without weight bearing. Using casts, the left ankles of 11 healthy males were immobilized for 2 weeks. Subjects were instructed to walk using crutches with no weight bearing during the period. Subjects were divided randomly into two groups: a restriction of blood flow (RBF) group (application of external compressive force of 50 mm Hg) and a control (CON) group (no intervention). We measured changes in the muscle strength of the knee extensor-flexor and ankle plantar flexor. The percent changes in knee extensor torque at 60°/s under eccentric contraction in the RBF group were significantly smaller than in the CON group (-12.5±10.7% and -30.1±10.9%, p<0.05). The percent changes in knee flexor torque when performing an eccentric contraction at 60°/s, an isometric contraction, or a concentric contraction at both 60 and 300°/s in the RBF group were significantly smaller than those in the CON group (p<0.05). In conclusion, our results show that repetitive restriction of blood flow with 50 mm Hg cuff pressure to the lower extremity reduces muscular weakness induced by chronic unloading.

Topics: Ankle; Humans; Immobilization; Isometric Contraction; Knee; Male; Muscle Weakness; Muscle, Skeletal; Muscular Disorders, Atrophic; Pressure; Regional Blood Flow; Torque; Weight-Bearing; Young Adult

This study investigated whether regular alpine skiing could reverse sarcopenia and muscle weakness in older individuals. Twenty-two older men and women (67 ± 2 years) underwent 12 weeks of recreational skiing, two to three times a week, each session lasting ∼ 3.5 h. An age-matched, inactive group (n=20, 67 ± 4 years) served as a control (CTRL). Before and after the training period, knee extensors muscle thickness (T(m) ), pennation angle (θ) and fascicle length (L(f) ) of the vastus lateralis muscle were measured by ultrasound. Maximum isokinetic knee extensor torque (MIT) at an angular velocity of 60°/s was measured by dynamometry. After the training, T(m) increased by 7.1% (P<0.001), L(f) by 5.4% (P<0.02) and θ by 3.4% (P<0.05). The increase in T(m) was matched by a significant gain in MIT (13.3%, P<0.001). No significant changes, except for a decrease in θ (2.1%, P<0.02), were found in the CTRL group. The gain in T(m) in the training group correlated significantly with an increase in the focal adhesion kinase content, pointing to a primary role of this mechano-sensitive protein in sarcomere remodeling with muscle hypertrophy. Overall, the results show that alpine skiing is an effective intervention for combating sarcopenia and weakness in old age.

Topics: Adaptation, Physiological; Age Factors; Aged; Aging; Analysis of Variance; Female; Humans; Male; Muscle Contraction; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Sarcopenia; Skiing; Statistics as Topic; Torque; Weight-Bearing

Arthrogenic muscle inhibition (AMI) contributes to quadriceps weakness and atrophy in knee arthritis and following joint injury. This laboratory-based study examined the efficacy of cryotherapy in reducing quadriceps AMI caused by intraarticular swelling.. Sixteen subjects without knee pathology participated, and were randomly assigned to a cryotherapy (n = 8) or control (n = 8) group. Surface electromyography (EMG) from vastus medialis and quadriceps torque measurements were recorded during maximum effort isometric contractions. All subjects then received an experimental joint infusion, whereby dextrose saline was injected into the knee to an intraarticular pressure of 50 mm Hg. EMG and torque measurements were repeated. Thereafter, the cryotherapy group had ice applied to the knee for 20 minutes while the control group did not receive an intervention. EMG and torque measurements were again collected. Quadriceps peak torque, muscle fiber conduction velocity (MFCV), and the root mean square (RMS) of EMG signals from vastus medialis were analyzed.. Quadriceps peak torque, MFCV, and RMS decreased significantly following joint infusion (P < or = 0.001). Cryotherapy led to a significant increase in quadriceps torque and MFCV compared with controls (P < 0.05). The difference in RMS did not reach statistical significance (P = 0.13).. The study demonstrated that cryotherapy is effective in reducing AMI induced by swelling. Cryotherapy may allow earlier and more effective quadriceps strengthening to occur in patients with knee joint pathology.

Topics: Adult; Cryotherapy; Electromyography; Female; Humans; Injections, Intra-Articular; Knee Injuries; Knee Joint; Male; Middle Aged; Models, Theoretical; Muscle Contraction; Muscle Weakness; Neural Conduction; Quadriceps Muscle; Sodium Chloride; Torque

The purpose of this study was to evaluate the effect of basketball training on the muscle strength of adults with mental retardation (MR). Twenty-four adults with and without MR were separated into 3 groups. Eight adults (mean age 25.4 years) with normal IQ constituted the control group (NIQ). Eight adults (mean age 26.5 years) with MR and all participating in a 4-year systematic basketball exercise program constituted the trained group (MR-T), and 8 adults (mean age 25.3 years) with MR exercised occasionally for recreational reasons formed the MR-R group. Parameters measured were isometric and isokinetic concentric and eccentric muscle strength. All subjects performed a leg strength test on a Cybex Norm isokinetic dynamometer. Analysis of variance was used to examine mean differences between the values of the 3 groups. A significance level of 0.05 was used for all tests. The NIQ group showed a statistically significant difference in all measured values compared to the MR groups. The MR-T group presented higher absolute and relative torque scores for both knee extensors and flexors than the MR-R group, whereas the MR-R group presented statistically higher antagonistic activity for both knee extensors and flexors than the MR-T group. In addition, both MR groups presented statistically higher antagonistic activity for both knee extensors and flexors compared to the NIQ group. Data support participation on a systematic and well-designed basketball training program to improve muscle strength levels of adults with MR. Participation in basketball without necessarily focusing on developing specific fitness components may be an effective training strategy for the promotion of strength of adults with MR.

Topics: Adult; Analysis of Variance; Basketball; Cross-Sectional Studies; Electromyography; Exercise Test; Humans; Intellectual Disability; Isometric Contraction; Isotonic Contraction; Leg; Male; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Physical Education and Training; Sedentary Behavior; Torque

Controlled laboratory study. To determine the effects of pulse duration and stimulation duration on the evoked torque after controlling for the activated area by using magnetic resonance imaging (MRI).. Neuromuscular electrical stimulation (NMES) is commonly used in the clinic without considering the physiological implications of its parameters.. Seven able-bodied, college students (mean +/- SD age, 28 +/- 4 years) participated in this study. Two NMES protocols were applied to the knee extensor muscle group in a random order. Protocol A applied 100-Hz, 450-microsecond pulses for 5 minutes in a 3-seconds-on 3-seconds-off duty cycle. Protocol B applied 60-Hz, 250-microsecond pulses for 5 minutes in a 10-seconds-on 20-seconds-off duty cycle. The amplitude of the current was similar in both protocols. Torque, torque time integral, and normalized torque for the knee extensors were measured for both protocols. MRI scans were taken prior to, and immediately after, each protocol to measure the cross-sectional area of the stimulated muscle.. The skeletal muscle cross-sectional areas activated after both protocols were similar. The longer pulse duration in protocol A elicited 22% greater torque output than that of protocol B (P<.05). After considering the activated area in both protocols, the normalized torque with protocol A was 38% greater than that with protocol B (P<.05). Torque time integral was 21% greater with protocol A (P = .029). Protocol B failed to maintain torque at the start and the end of the 10-second activation.. Longer pulse duration, but not stimulation duration, resulted in a greater evoked and normalized torque compared to the shorter pulse duration, even after controlling for the activated muscular cross-sectional areas with both protocols.. Therapy, level 5.

Topics: Adult; Electric Stimulation Therapy; Female; Humans; Knee Joint; Magnetic Resonance Imaging; Male; Muscle Strength Dynamometer; Muscle Weakness; Muscular Atrophy; Torque; Young Adult

An inability of the nervous system to fully activate the muscle is one factor that can contribute to age-related muscle weakness. Superimposed electrical stimulation can be used to determine voluntary muscle activation (VA). The aim of this study was to assess VA of the quadriceps muscle in healthy older and younger subjects.. Electrical stimulation causes moderate discomfort in younger subjects, but no study has assessed discomfort in older subjects. The quadriceps muscle in 20 moderately active older subjects (mean age, 75 yrs) and 12 younger subjects (mean age, 25 yrs) was stimulated during two maximal voluntary contractions using a 100-Hz pulse train. A visual analog scale for pain (VAS-pain) was used to evaluate discomfort.. Ability to activate the quadriceps muscle was generally very high, and there was no significant difference between the older (mean, 0.96) and younger (mean, 0.98) subjects. Discomfort did not differ between the older (mean VAS-pain score, 41 mm) and younger (mean VAS-pain score, 37 mm) subjects.. Our results indicate that healthy, moderately active older subjects have the ability to almost complete VA of the quadriceps muscle and that discomfort during electrical stimulation is generally moderate.

Topics: Adult; Age Factors; Aged; Electric Stimulation; Female; Humans; Male; Motor Neurons; Muscle Contraction; Muscle Weakness; Pain; Pain Measurement; Quadriceps Muscle; Torque

Unlike individuals with mild stroke, individuals with severe stroke are constrained to stereotypical movement patterns attributed to abnormal coupling of shoulder abductors with elbow flexors, and shoulder adductors with elbow extensors. Whether abnormal muscle coactivation and associated joint torque patterns can be changed in this population is important to determine given that it bears on the development of effective rehabilitation interventions. Eight subjects participated in a protocol that was designed to reduce abnormal elbow/shoulder joint torque coupling by training them to generate combinations of isometric elbow and shoulder joint torques away from the constraining patterns. After training, subjects demonstrated a significant reduction in abnormal torque coupling and a subsequent significant increase in ability to generate torque patterns away from the abnormal pattern. We suggest the rapid time-course of these changes reflects a residual capacity of the central nervous system to adapt to a novel behavioral training environment.

Topics: Adult; Aged; Aged, 80 and over; Elbow Joint; Electromyography; Female; Humans; Isometric Contraction; Male; Middle Aged; Movement Disorders; Muscle Weakness; Muscle, Skeletal; Physical Therapy Modalities; Range of Motion, Articular; Recovery of Function; Shoulder Joint; Stroke; Stroke Rehabilitation; Torque; Treatment Outcome

We established reliability of upper-limb muscle performance in adults with post-stroke hemiparesis. Ten adults with post-stroke hemiparesis (51.5 +/- 34.5 months) performed isokinetic concentric shoulder flexion, elbow flexion, and extension at 3 criterion speeds (30 degrees/s, 75 degrees/s, and 120 degrees/s) on 3 separate occasions (Days 1, 7, and 49). As several participants were unable to reach criterion speeds, actual speed and power were also analyzed. Relative reliability (intraclass correlation coefficient-ICC) was excellent for torque and power (0.82 to 0.98) but less consistent for speed (0.63 to 0.99). Absolute reliability (standard error of measurement-%SEM) ranged between 0% to 34%. No systematic errors were observed across sessions. Smallest real differences (SRD) ranged between 4-11Nm for torque and 3-24W for power. Shoulder flexion, elbow flexion, and elbow extension torque, speed, and power can be measured reliably following stroke. Given that many of these individuals demonstrate inability to generate torque at preselected speeds, power may be a more valid indicator of muscle performance.

Topics: Aged; Arm; Elbow Joint; Evidence-Based Medicine; Female; Humans; Male; Middle Aged; Muscle Weakness; Paresis; Physical Therapy Modalities; Reproducibility of Results; Shoulder Joint; Torque

Hip adductor spasticity and strength in participants with cerebral palsy (CP) were quantified before and after selective dorsal rhizotomy (SDR) and intensive physical therapy. Twenty-four participants with cerebral palsy (CP group) and 35 non-disabled participants (ND controls) were tested with a dynamometer (OP group: mean age 8 years 5 months, 13 males, 11 females; ND group: mean age 8 years 6 months, 19 males, 16 females). According to the Gross Motor Function Classification System (GMFCS), of the 24 participants with CP, eight were at level I, six were at level II, and 10 participants were at level III. For the spasticity measure, the dynamometer quantified the resistive torque of the hip adductors during passive abduction at 4 speeds. The adductor strength test recorded a maximum concentric contraction. CP group spasticity was significantly reduced following SDR and adductor strength was significantly increased after surgery. Both pre- and postoperative values remained significantly less than the ND controls. Spasticity results agreed with previous studies indicating a reduction. Strength results conflicted with previous literature subjectively reporting a decrease following SDR. However, results agreed with previous objective investigations examining knee and ankle strength, suggesting strength did not decrease following SDR.

Topics: Adolescent; Ankle; Cerebral Palsy; Child; Child, Preschool; Female; Ganglia, Spinal; Hip; Humans; Knee; Male; Muscle Spasticity; Muscle Weakness; Physical Therapy Modalities; Prospective Studies; Range of Motion, Articular; Rhizotomy; Torque; Treatment Outcome

Isokinetic strength of knee extension and flexion was measured at two speeds of movement in 23 patients with Parkinson's disease, to clarify whether muscle weakness is inherent to the disease. To counteract normal variation among subjects, we selected patients with symptoms completely or largely confined to one side and compared sides for each patient. The affected side was weaker than the other in both slow and fast movements early in the disease. In more advanced disease, the difference between sides diminished at the slow speed but remained significant at the faster speed. These observations suggest that weakness is inherent to Parkinson's disease and influenced by movement speed.

Topics: Aged; Exercise Test; Female; Humans; Knee; Leg; Male; Middle Aged; Movement; Muscle Weakness; Parkinson Disease; Torque

Following active lengthening or shortening contractions, isometric steady-state torque is increased (residual force enhancement; rFE) or decreased (residual force depression; rFD), respectively, compared to fixed-end isometric contractions at the same muscle length and level of activation. Though the mechanisms underlying this history dependence of force have been investigated extensively, little is known about the influence of exercise-induced muscle weakness on rFE and rFD.. Assess rFE and rFD in the dorsiflexors at 20%, 60%, and 100% maximal voluntary torque (MVC) and activation matching, and electrically stimulated at 20% MVC, prior to, 1 h following, and 24 h following 150 maximal eccentric dorsiflexion contractions.. Twenty-six participants (13 male, 24.7 ± 2.0y; 13 female, 22.5 ± 3.6y) were seated in a dynamometer with their right hip and knee angle set to 110° and 140°, respectively, with an ankle excursion set between 0° and 40° plantar flexion (PF). MVC torque, peak twitch torque, and prolonged low frequency force depression were used to assess eccentric exercise-induced neuromuscular impairments. History-dependent contractions consisted of a 1 s isometric (40°PF or 0°PF) phase, a 1 s shortening or lengthening phase (40°/s), and an 8 s isometric (0°PF or 40°PF) phase.. Following eccentric exercise; MVC torque was decreased, prolonged low frequency force depression was present, and both rFE and rFD increased for all maximal and submaximal conditions.. The history dependence of force during voluntary torque and activation matching, and electrically stimulated contractions is amplified following eccentric exercise. It appears that a weakened neuromuscular system amplifies the magnitude of the history-dependence of force.

Topics: Electromyography; Female; Humans; Isometric Contraction; Male; Mechanical Phenomena; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Torque

Electromechanical delay (EMD) is the time delay between the onset of muscle activity and the onset of force/joint torque. This delay appears to be linked to muscular contraction efficiency. However, to our knowledge, limited evidence is available regarding the magnitude of the EMD in stroke-impaired muscles. Accordingly, this study aims to quantify the EMD in both paretic and non-paretic triceps surae muscles of chronic hemispheric stroke survivors, and to investigate whether the EMD is related to voluntary force-generating capacity in this muscle group. Nine male chronic stroke survivors were asked to perform isometric plantarflexion contractions at different force levels and at different ankle joint angles ranging from maximum plantarflexion to maximum dorsiflexion. The surface electromyograms were recorded from triceps surae muscles. The longest EMD among triceps surae muscles was chosen as the EMD for each side. Our results revealed that the EMD in paretic muscles was significantly longer than in non-paretic muscles. Moreover, both paretic and non-paretic muscles showed a negative correlation between the EMD and maximum torque-generating capacity. In addition, there was a strong positive relationship between the EMD and shear wave speed in paretic muscles as well as a negative relationship between the EMD and passive ankle joint range of motion. These findings imply that the EMD may be a useful biomarker, in part, associated with contractile and material properties in stroke-impaired muscles.

Topics: Aged; Chronic Disease; Electromyography; Humans; Isometric Contraction; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Range of Motion, Articular; Stroke; Survivors; Torque

We compared hip and knee isometric muscle torque between individuals with chronic ankle instability (CAI), those who have sustained one ankle sprain with no ongoing problems (copers) and healthy controls. Our secondary objective was to compare balance between groups and investigate the relationship between muscle torque and balance.. Cross-sectional study.. 22 CAI, 20 copers and 22 uninjured participants were tested. Isometric torque (normalised to body mass (Nm/kg)) was measured using a rigidly-fixated hand-held dynamometer. Balance was assessed with the Y-balance test.. Knee and hip flexor and extensor, and hip adductor and abductor muscle torque was less in individuals with CAI compared to controls (standardised mean difference (SMD) >1.2). Hip and knee flexor and extensor muscle torque was less in CAI participants than copers (SMD: 0.69-1.1). Hip external and internal rotator torque did not differ between groups. There was no difference in hip or knee muscle torque between controls and copers (SMD: 0.01-0. 54). Balance was impaired in CAI participants compared to copers and controls in all directions. There was a strong positive correlation between posterolateral Y-balance test performance and torque of the hip adductors (r=0.53), flexors (r=0.52) and extensors (r=0.50).. Individuals with CAI have weak knee and hip muscles compared to copers and controls. Hip strength was shown to be related to posterolateral balance performance. Future studies may investigate the effect of hip and knee strengthening exercise on ongoing ankle problems, such as episodic giving way in individuals with CAI.

Topics: Adolescent; Adult; Ankle Injuries; Chronic Disease; Female; Hip; Humans; Isometric Contraction; Joint Instability; Knee; Male; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Postural Balance; Range of Motion, Articular; Torque; Young Adult

This study aimed to determine deficits in knee extensor muscle function through the torque-time and torque-velocity relationships and whether these deficits are associated with reduced functional performance in postmenopausal women with knee osteoarthritis (KOA). A clinical sample of postmenopausal women with established KOA (n = 18, ≥55 years) was compared to an age-matched healthy control sample (CON) (n = 26). The deficits in different parameters of the knee extensor torque-time (maximal isometric torque and rate of torque development) and torque-velocity relationship (maximum muscle power, maximal velocity and torque at 0-500°·s

Topics: Aged; Cross-Sectional Studies; Exercise Test; Female; Humans; Middle Aged; Muscle Weakness; Osteoarthritis, Knee; Postmenopause; Torque

To examine differences in shoulder internal rotation (IR) torque among youth pitchers of above and below average relative glenohumeral (GH) rotation strength levels. It was hypothesized that differences in IR torque during the pitching motion would could be explained by differences in relative IR and external rotation (ER) strength.. Descriptive laboratory study.. Isometric GH rotation strength and upper extremity pitching mechanics were assessed in 78 male youth baseball pitchers (12.7±2.0yrs; 1.63±14.0m; 56.9±12.4kg). Shoulder IR torque during the pitch was examined at maximum humeral external rotation (MER) and throughout the arm acceleration phase (ACC). Multivariate analysis of covariance (MANCOVA) was used to examine the differences in pitching IR torque between GH strength groups.. A significant main effect of ER strength on the dependent variables was present after controlling for fastball velocity (λ=0.855, F. Weakness of the GH ER musculature partially accounts for increased shoulder IR torque during pitching.

Topics: Adolescent; Baseball; Biomechanical Phenomena; Child; Humans; Male; Muscle Weakness; Shoulder Joint; Torque

Ultrasound imaging provides a cost-effective method of measuring quadriceps morphology, which may be related to self-reported function after anterior cruciate ligament reconstruction (ACLR).. To compare quadriceps morphology and strength between limbs in individuals with ACLR and matched control limbs and determine their associations with self-reported function.. Cross-sectional study.. Research laboratory.. Forty-two individuals with ACLR (females = 66%; age = 21.8 ± 2.6 years; time since ACLR = 50.5 ± 29.4 months) and 37 controls (females = 73%; age = 21.7 ± 1.2 years).. Quadriceps peak torque (PT) and rate of torque development were assessed bilaterally. Ultrasonography was used to measure the cross-sectional area (CSA) and echo intensity (EI) of the rectus femoris, vastus lateralis (VL), and vastus medialis. Self-reported function was assessed via the International Knee Documentation Committee (IKDC) score and Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales. Paired-samples. Isometric PT did not differ between limbs or groups. Involved limbs had a lower rate of torque development compared with the control (. Quadriceps morphology was associated with self-reported function in individuals with ACLR and may provide unique assessments of quadriceps function.

Topics: Anterior Cruciate Ligament Injuries; Anterior Cruciate Ligament Reconstruction; Athletic Injuries; Cross-Sectional Studies; Female; Humans; Knee; Knee Joint; Male; Muscle Strength; Muscle Weakness; Quadriceps Muscle; Quality of Life; Self Report; Torque; Ultrasonography; Young Adult

One of the possible mechanisms leading to secondary impingement syndrome may be the strength imbalance of shoulder rotators which is known as functional control ratio (FCR). The FCR is a ratio dividing the eccentric peak torque of the external rotators by the concentric peak torque of the internal rotators. Previous studies have focused on the reproducibility and reliability of isokinetic assessment, but there is little information on the influence of variable shoulder positions on FCR.. To compare shoulder FCR across 3 different shoulder abduction positions during isokinetic assessment.. Cross-sectional study.. Biomechanics laboratory.. Thirty-one healthy young university students (age 22.35 [0.95] y, weight 60.52 [9.31] kg, height 168.23 [9.47] cm).. The concentric peak torque of internal rotators and eccentric peak torque of external rotators of right shoulder were measured on an isokinetic dynamometer.. Concentric peak torque of the internal rotators and eccentric peak torque of the external rotators, measured using an isokinetic dynamometer.. The concentric peak torque of internal rotators was significantly lower at 120° shoulder abduction compared with other positions (P < .001). The FCR was significantly higher at 120° shoulder abduction than 90° (P = .002) or 60° (P < .001) shoulder abduction because of the lower concentric peak torque. No significant difference was found in the FCR between the other 2 shoulder positions (P = .14).. Shoulder position variations may influence FCR because of weakness of the internal rotators. Rehabilitation and injury prevention training programs should specifically focus on strengthening the internal rotators at more elevated angles of shoulder abduction.

Topics: Body Weight; Cross-Sectional Studies; Female; Humans; Kinetics; Male; Muscle Weakness; Pectoralis Muscles; Posture; Reproducibility of Results; Rotator Cuff; Shoulder; Shoulder Joint; Statistics, Nonparametric; Torque; Young Adult

To compare rate of force development (RFD) and isometric muscle strength of the hip abductors and extensors; and the thickness and the amount of non-contractile tissue of the gluteus medius and maximus between females with and without patellofemoral pain (PFP).. Cross-sectional study.. Fifty-four physically active females (27 with PFP and 27 healthy individuals) were studied. Hip muscle isometric strength and RFD was evaluated using isokinetic dynamometry. RFD was measured until 30%, 60%, and 90% of the maximal isometric torque (MIT). Hip muscle morphology was evaluated using ultrasonography.. The PFP group possessed slower RFD compared to the control group by 33% for hip abductors until 90%MIT (-0.23%/ms, 95%CI -0.44 to -0.02, ES=0.59); by 51% for hip extensors until 30%MIT (-0.42%/ms, 95%CI -0.66 to -0.18, ES=0.97); and by 55% for hip extensors until 60%MIT (-0.36%/ms, 95%CI -0.60 to -0.12, ES=0.81). The PFP group possessed reduced isometric torque compared to the control group by 10% for hip abduction (-16.0Nm/kg×100, 95% CI -30.2 to -1.9, ES=0.61) and by 15% for hip extension (-30.1Nm/kg×100, 95%CI -51.4 to -8.9, ES=0.76). No significant between group differences for the thickness and the amount of non-contractile tissue of the gluteus medius and maximus were identified.. Females with PFP have deficits in isometric strength and RFD in hip abduction and extension. RFD deficits are greater than strength deficits which may highlight their potential importance. Hip muscle strength and RFD deficits do not appear to be explained by muscle thickness or proportion of non-contractile tissue of the gluteal musculature as measured by ultrasound.

Topics: Adolescent; Adult; Case-Control Studies; Cross-Sectional Studies; Female; Hip; Humans; Isometric Contraction; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Patellofemoral Pain Syndrome; Torque; Ultrasonography; Young Adult

The contributions of fiber atrophy, fiber loss, in situ specific force, and voluntary activation to weakness in sarcopenia remain unclear. To investigate, 40 older (20 women; age 72 ± 4 years) and 31 younger adults (15 women, age 22 ± 3 years) completed measurements. The knee extensor maximal voluntary torque (MVC) was measured as well as voluntary activation, patella tendon moment arm length, muscle volume, and fascicle architecture to estimate in situ specific force. Fiber cross-sectional area (FCSA), fiber numbers, and connective tissue contents were also estimated from vastus lateralis biopsies. The MVC, quadriceps volume, and specific force were 39%, 28%, and 17% lower, respectively, in old compared with young, but voluntary activation was not different. The difference in muscle size was due in almost equal proportions to lower type II FCSA and fewer fibers. Five years later (n = 23) the MVC, muscle volume and voluntary activation in old decreased an additional 12%, 6%, and 4%, respectively, but there was no further change in specific force. In situ specific force declines relatively early in older age and reduced voluntary activation occurs later, but the overall weakness in sarcopenia is mainly related to loss of both type I and II fibers and type II fiber atrophy.

Topics: Adult; Aged; Aged, 80 and over; Aging; Female; Humans; Knee Joint; Longitudinal Studies; Male; Muscle Contraction; Muscle Fibers, Skeletal; Muscle Strength; Muscle Weakness; Muscular Atrophy; Sarcopenia; Torque; Young Adult

Patients suffering from neurological and orthopedic diseases or injuries usually have mobility impairment problems, and they require customized rehabilitation training to recover. In recent years, robotic assistive devices have been widely studied for gait rehabilitation. In this paper, methods to determine user-adaptive assistance of assistive knee braces (AKBs) in gait rehabilitation are investigated. A fuzzy expert system, which takes a patient's physical condition and gait analysis results as inputs, is proposed to configure suitable levels of different assistive functions of the AKB. During gait rehabilitation, the AKB generates a reference knee trajectory according to the patient's individual gait pattern, and the interaction force is controlled through a hybrid impedance controller considering the individual assistive function configuration. The proposed methods are verified through clinical pilot studies of a patient with lower limb weakness. Experimental results show that AKB with the proposed control strategies can provide effective assistance to improve the patient's gait performance during gait rehabilitation.

Topics: Adaptation, Physiological; Biomechanical Phenomena; Braces; Computer Simulation; Fuzzy Logic; Gait Disorders, Neurologic; Humans; Knee; Muscle Weakness; Orthotic Devices; Robotics; Self-Help Devices; Torque

Osteoarthritis is the most prevalent rheumatic disease in the population and is characterized by limitation of main functional activities of daily living, as the gait. Muscle strength is a variable that may be related to performance in daily tasks.Therefore, we to analyze the gait pattern in individuals with knee osteoarthritis (KOA) and to determine associations of gait variables with the level of muscle strength of knee extensors.. Sixty-seven female volunteers divided into 2 groups, a KOA group (KOAG, n = 36, 66.69 ± 7.69 years) and control (n = 31, 63.68 ± 6.97 years), participated in the study. The volunteers walked on a 10-m platform at their usual gait speed, using 2 pressure sensors positioned at the base of the hallux and calcaneus. The mean step time, support and double support times, swing time and gait speed were calculated. The evaluation of the quadriceps isometric torque was performed in an extensor chair, with hip and knee flexion at 90°. The procedure consisted of three maximal contractions of knee extension. Peak torque was determined by the highest torque value obtained after the onset of muscle contraction. For statistical analysis, one-way ANOVA and Pearson's correlation were used, with p <  0.05.. The KOAG had a 54.76% longer support time, a 13% longer step time (p <  0.001), a 30% decrease in swing time (p <  0.001) and a 10.7% decrease in gait speed (p = 0.001) compared with controls. The quadriceps isometric torque was 34% (p = 0.001) lower in the KOAG. There was a correlation between kinematic variables and quadriceps torque.. Weakness of the quadriceps muscle in women with KOA influences gait pattern, resulting in reduced speed associated with a shorter swing time and longer support time.

Topics: Aged; Analysis of Variance; Case-Control Studies; Female; Gait; Gait Analysis; Humans; Isometric Contraction; Middle Aged; Muscle Contraction; Muscle Weakness; Osteoarthritis, Knee; Quadriceps Muscle; Torque; Walking Speed

This study examines the electromyogram (EMG)-torque relation for chronic stroke survivors using a novel EMG complexity representation. Ten stroke subjects performed a series of submaximal isometric elbow flexion tasks using their affected and contralateral arms, respectively, while a 20-channel linear electrode array was used to record surface EMG from the biceps brachii muscles. The sample entropy (SampEn) of surface EMG signals was calculated with both global and local tolerance schemes. A regression analysis was performed between SampEn of each channel's surface EMG and elbow flexion torque. It was found that a linear regression can be used to well describe the relation between surface EMG SampEn and the torque. Each channel's root mean square (RMS) amplitude of surface EMG signal in the different torque level was computed to determine the channel with the highest EMG amplitude. The slope of the regression (observed from the channel with the highest EMG amplitude) was smaller on the impaired side than on the nonimpaired side in 8 of the 10 subjects, regardless of the tolerance scheme (global or local) and the range of torques (full or matched range) used for comparison. The surface EMG signals from the channels above the estimated muscle innervation zones demonstrated significantly lower levels of complexity compared with other channels between innervation zones and muscle tendons. The study provides a novel point of view of the EMG-torque relation in the complexity domain, and reveals its alterations post stroke, which are associated with complex neural and muscular changes post stroke. The slope difference between channels with regard to innervation zones also confirms the relevance of electrode position in surface EMG analysis.

Topics: Adult; Aged; Aged, 80 and over; Chronic Disease; Electromyography; Female; Humans; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Signal Processing, Computer-Assisted; Stroke; Torque

Muscle weakness determines functional impairment in spastic cerebral palsy (SCP). Measurement of specific force (SF) allows for strength comparison with unimpaired populations (controls) accounting for neural (activation and coactivation), architectural (fascicle length and pennation angle), and structural differences (moment arm length).. Medial gastrocnemius (MG) SF (and its determinants) was assessed in both paretic and non-paretic legs of 11 men with SCP and 11 age-matched controls during plantarflexion maximal voluntary isometric contraction (MVIC).. SCP fascicles were 28% longer than control fascicles (P < 0.05). Pennation angle of SCP patients was 41% smaller than in controls. The physiological cross-sectional area of SCP MG patients was 47% smaller than in controls (P < 0.05). There was no difference in SF between controls and SCP patients.. Weakness in SCP is primarily attributable to deficits in agonist activation and muscle size; consequently, SF measured in the MG is similar between SCP and controls. Muscle Nerve 56: 298-306, 2017.

Topics: Achilles Tendon; Adolescent; Adult; Ankle Joint; Case-Control Studies; Cerebral Palsy; Electric Stimulation; Electromyography; Humans; Isometric Contraction; Male; Movement; Muscle Weakness; Muscle, Skeletal; Range of Motion, Articular; Statistics, Nonparametric; Torque; Young Adult

Ankle sprain is the most common sport-related injury and eccentric weakness of ankle evertors is regarded as a significant muscular deficit related to chronic ankle instability. However, the eccentric performance of the evertors is rarely assessed by clinicians because procedures used for research purposes (i.e. isokinetic tests) are not easily applicable in daily practice.. The present study assessed the ability of two different testing procedures to distinguish between groups of 12 healthy subjects or 12 patients suffering from chronic ankle instability. On the one hand, the strength of evertors was assessed with a goldstandard isokinetic procedure. On the other hand, we assessed the ability of the subjects to control ankle inversion during weight bearing (functional standing test).. Data showed no significant difference between groups for isokinetic peak torque values normalized to body weight. Conversely, the functional test revealed a significantly impaired ability to control ankle inversion during weight bearing in subjects with chronic ankle instability.. This suggests that this easy-to-apply functional test is better suited compared to isokinetic testing procedures to assess weakness of evertors in patients suffering from chronic ankle instability. Moreover, this test may also be used to objectively monitor improvements during rehabilitation or progression in prevention protocols.

Topics: Ankle Injuries; Ankle Joint; Female; Humans; Joint Instability; Male; Muscle Strength Dynamometer; Muscle Weakness; Postural Balance; Sprains and Strains; Torque; Weight-Bearing; Young Adult

Topics: Adaptation, Physiological; Adenylate Kinase; Animals; Diaphragm; Disease Models, Animal; Male; Matrix Metalloproteinase 9; Mice; Mice, Inbred C57BL; Mice, Inbred mdx; Muscle Contraction; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Muscular Dystrophy, Animal; Muscular Dystrophy, Duchenne; Physical Conditioning, Animal; Torque; Up-Regulation

It is theorized that increased dynamic knee valgus relates to decreased hip posterolateral muscle strength.. The aim here was to assess the relationship between the frontal plane projection angle (FPPA) of the knee and hip and trunk muscle strength in women with and without patellofemoral pain (PFP).. The sample comprised 43 women: Patellofemoral Pain Group (PPG, n = 22) and Control Group (CG, n = 21). Muscle strength for hip abduction, extension, external rotation and lateral core were measured using a handheld dynamometer. The FPPA was recorded during step-down.. The PPG showed a deficit for hip muscles torque and increased FPPA (P < 0.05). Negative correlation of the FPPA-Peak was found in the CG for the hip abductor (r = -0.31) and posterolateral complex (r = -0.32) (P < 0.05). In the PPG, the FPPA-Peak showed a moderate negative correlation to the torque of external rotators and posterolateral hip muscles, although this correlation did not reach statistical significance.. These findings suggest that women with patellofemoral pain present greater dynamic knee valgus and hip muscle weakness. Abductor and posterolateral hip muscles strength are associated with increased FPPA only in the pain-free population.

Topics: Adolescent; Adult; Biomechanical Phenomena; Case-Control Studies; Cross-Sectional Studies; Female; Hip Joint; Humans; Knee Joint; Middle Aged; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Patellofemoral Pain Syndrome; Rotation; Torque; Torso; Young Adult

This study aimed to compare hip abductor muscle strength between individuals with symptomatic, unilateral gluteal tendinopathy (GT), and asymptomatic controls.. Fifty individuals with GT age between 35 and 70 yr and 50 sex- and age-comparable controls were recruited from the community. Maximal isometric strength (torque normalized to body mass) of the hip abductors was recorded in the supine position using an instrumented manual muscle tester. A two-way mixed ANCOVA, with covariates of self-reported pain during testing and pain limiting maximum effort, was used to compare hip abductor strength of the symptomatic and asymptomatic hip between GT and control individuals. Data were expressed as mean and SD, with the pairwise comparisons expressed as mean differences and 95% confidence intervals.. Individuals with GT demonstrated significantly lower hip abductor torque of both their symptomatic and asymptomatic hip than healthy controls (both P < 0.05), with mean strength deficits of 0.35 N·m·kg (32%) on the symptomatic hip and 0.25 N·m·kg (23%) on the asymptomatic hip. In individuals with GT, the symptomatic hip was significantly weaker than the asymptomatic hip with a mean strength deficit of 0.09 N·m·kg (11%) (P < 0.05).. People with unilateral GT demonstrate significant weakness of the hip abductor muscles bilaterally when compared with healthy controls. Although it is not clear whether hip weakness precedes GT or is a consequence of the condition, the findings provide a basis to consider hip abductor muscle weakness in the treatment plan for management of GT.

Topics: Adult; Aged; Case-Control Studies; Exercise Test; Female; Hip; Humans; Male; Middle Aged; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Tendinopathy; Torque

Foot and ankle structures are the most commonly affected in people with gout. However, the effect of gout on foot and ankle muscle strength is not well understood. The primary aim of this study was to determine whether differences exist in foot and ankle muscle strength for plantarflexion, dorsiflexion, inversion and eversion between people with gout and age- and sex-matched controls. The secondary aim was to determine whether foot and ankle muscle strength was correlated with foot pain and disability.. Peak isokinetic concentric muscle torque was measured for ankle plantarflexion, dorsiflexion, eversion and inversion in 20 participants with gout and 20 matched controls at two testing velocities (30°/s and 120°/s) using a Biodex dynamometer. Foot pain and disability was measured using the Manchester Foot Pain and Disability Index (MFPDI).. Participants with gout demonstrated reduced muscle strength at both the 30°/s and 120°/s testing velocities for plantarflexion, inversion and eversion (P<0.05). People with gout also displayed a reduced plantarflexion-to-dorsiflexion strength ratio at both 30°/s and 120°/s (P<0.05). Foot pain and disability was higher in people with gout (P<0.0001) and MFPDI scores were inversely correlated with plantarflexion and inversion muscle strength at the 30°/s testing velocity, and plantarflexion, inversion and eversion muscle strength at the 120°/s testing velocity (all P<0.05).. People with gout have reduced foot and ankle muscle strength and experience greater foot pain and disability compared to controls. Foot and ankle strength reductions are strongly associated with increased foot pain and disability in people with gout.

Topics: Adult; Aged; Ankle; Case-Control Studies; Cross-Sectional Studies; Female; Foot; Gout; Humans; Male; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Pain; Torque

The purpose of this study was to determine whether the mechanical contribution of ankle muscles in the upright stance differed among young adults (YA) (n=10, age: ~24.3), elderly non-fallers (ENF) (n=12, age: ~77.3) and elderly fallers (EF) (n=20, age: ~80.7). Torque and electromyographic (EMG) activity were recorded on the triceps surae and tibialis anterior during maximum and submaximum contractions in the seated position. EMG activity was also recorded in subjects standing still. Plantar flexor (PF) and dorsal flexor (DF) torques generated in the upright posture were estimated from the torque-EMG relationship obtained during submaximum contractions in the seated position. Center of pressure (CoP) displacement was measured to quantify postural stability. Results showed that, in upright standing, EF generated greater ankle muscle relative torque (i.e. PF+DF torque in the upright stance/PF+DF during maximum isometric torque) than non-fallers (i.e. ENF, YA). The greater involvement of ankle muscles in EF was associated with higher CoP displacement. PF+DF torque in the upright stance was no different among the groups, but PF+DF torque during maximum effort was impaired in older groups compared with YA and was lower in EF than ENF. These results suggest that the postural stability impairment observed with aging is highly related to ankle muscle weakness.

Topics: Accidental Falls; Aged; Aged, 80 and over; Ankle Joint; Electromyography; Humans; Muscle Weakness; Muscle, Skeletal; Postural Balance; Torque; Young Adult

This study tested the hypothesis that rate of force development (RFD) would be a more sensitive indirect marker of muscle damage than maximum voluntary isometric contraction (MVC) peak torque. Ten men performed one concentric cycling and two eccentric cycling (ECC1, ECC2) bouts for 30 min at 60% of maximal concentric power output with 2 weeks between bouts. MVC peak torque, RFD, and vastus lateralis electromyogram amplitude and mean frequency were measured during a knee extensor MVC before, immediately after and 1-2 days after each bout. The magnitude of decrease in MVC peak torque after exercise was greater (P < 0.05) for ECC1 (11-25%) than concentric cycling (2-12%) and ECC2 (0-16%). Peak RFD and RFD from 0-30 ms, 0-50 ms, 0-100 ms, to 0-200 ms decreased (P < 0.05) immediately after all cycling bouts without significant differences between bouts, but RFD at 100-200 ms interval (RFD(100-200)) decreased (P < 0.05) at all time points after ECC1 (24-32%) and immediately after ECC2 (23%), but did not change after CONC. The magnitude of decrease in RFD(100-200) was 7-19% greater than that of MVC peak torque after ECC1 (P < 0.05). It is concluded that RFD(100-200) is a more specific and sensitive indirect marker of eccentric exercise-induced muscle damage than MVC peak torque.

Topics: Adult; Bicycling; Electromyography; Humans; Isometric Contraction; Male; Muscle Contraction; Muscle Strength; Muscle Weakness; Quadriceps Muscle; Time Factors; Torque; Young Adult

Because of the importance of hamstrings (HAM) and quadriceps (QUAD) strength for anterior cruciate ligament (ACL) injury prevention and the high incidence of ACL injury in ski racing, HAM and QUAD maximal and explosive strength were assessed in ski racers with and without ACL reconstruction (ACL-R).. Uninjured (n = 13 males, n = 8 females) and ACL-R (n = 3 males, n = 5 females, 25.0 ± 11.3 months after operation) elite ski racers performed maximal voluntary isometric HAM and QUAD contractions to obtain maximal torque (MVC) and rate of torque development (RTD) at 0-50, 0-100, 0-150, and 0-200 ms. MVC and RTD (per kilogram body mass) were calculated for the uninjured group to compare between sexes and to compare the control group with the ACL-R limb and unaffected limb of the ACL-R skiers. HAM/QUAD MVC and RTD strength ratios (H/Q ratios) were also compared.. The ACL-R limb demonstrated significant HAM and QUAD deficits compared with the contralateral limb for MVC and late-phase RTD (P < 0.05). Uninjured male skiers also displayed a limb difference for HAM MVC and RTD at 150 ms (P < 0.05). QUAD MVC and RTD deficits were observed in the affected limb of ACL-R skiers, which led to an inflated H/Q ratio (50 ms) compared with that in uninjured controls (P < 0.05). Compared with male skiers, females displayed greater relative HAM RTD (50 ms) and an elevated H/Q RTD ratio (50 ms), suggesting enhanced ACL protection (P < 0.05).. Because of the strength demands of ski racing, our results suggest the importance of including HAM and QUAD strength assessments in the physical evaluation of uninjured skiers. Furthermore, HAM and QUAD strength should be assessed over a long-term period after surgery to identify chronic strength deficits in ACL-R ski racers.

Topics: Adolescent; Adult; Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Anterior Cruciate Ligament Reconstruction; Female; Healthy Volunteers; Humans; Isometric Contraction; Knee Injuries; Male; Muscle Strength; Muscle Weakness; Quadriceps Muscle; Sex Factors; Skiing; Thigh; Torque; Young Adult

Quadriceps muscle weakness is common in knee osteoarthritis (OA). Reasons for weakness may include atrophy, reduction in the muscle fibers number, and changes in the muscle activation. It is uncertain when these muscular changes begin to appear. Therefore, the purpose of this study was to determine whether men with early stages of knee OA already had functional and quadriceps muscle morphologic alterations.. Forty men were divided into two groups: control group (healthy subjects) and OA group (subjects with knee OA). A biopsy of the vastus lateralis muscle was performed for morphometric analysis. Isokinetic evaluation of knee extensor torque, concentric and eccentric (90 and 180 degrees/sec), was performed simultaneously with vastus lateralis electromyographic activity evaluation.. Significant differences were found in knee extensor torque (P < 0.05) and in normalized root mean square (P < 0.01) during the eccentric contractions (both velocities), with higher values for the control group. No differences were found during concentric contractions. The OA group presented greater values of the minimum diameter of type 1 fibers and greater proportion and relative cross-sectional area of type 2b fibers (P < 0.05).. Men with early stages of knee OA do not present alterations of concentric strength but had decreased eccentric strength and morphologic quadriceps muscle changes, indicating neuromuscular adaptations.

Topics: Adult; Aged; Electromyography; Health Status; Humans; Knee Joint; Male; Middle Aged; Muscle Weakness; Osteoarthritis, Knee; Quadriceps Muscle; Range of Motion, Articular; Reference Values; Torque

Return to activity in the presence of quadriceps dysfunction may predispose individuals with anterior cruciate ligament reconstruction (ACLR) to long-term joint degeneration. Asymmetry may manifest during movement and result in altered knee-joint-loading patterns; however, the underlying neurophysiologic mechanisms remain unclear.. To compare limb symmetry of quadriceps neuromuscular function between participants with ACLR and participants serving as healthy controls.. Descriptive laboratory study.. Research laboratory.. A total of 22 individuals with ACLR (12 men, 10 women) and 24 individuals serving as healthy controls (12 men, 12 women).. Normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg), quadriceps central activation ratio (CAR) (%), quadriceps motor-neuron-pool excitability (Hoffmann reflex to motor wave ratio), and quadriceps active motor threshold (AMT) (% 2.0 T) were measured bilaterally and used to calculate limb symmetry indices for comparison between groups. We used analyses of variance to compare quadriceps Hoffmann reflex to motor wave ratio, normalized knee-extension MVIC torque, quadriceps CAR, and quadriceps AMT between groups and limbs.. The ACLR group exhibited greater asymmetry in knee-extension MVIC torque (ACLR group = 0.85 ± 0.21, healthy group = 0.97 ± 0.14; t44 = 2.26, P = .03), quadriceps CAR (ACLR group = 0.94 ± 0.11, healthy group = 1.00 ± 0.08; t44 = 2.22, P = .04), and quadriceps AMT (ACLR group = 1.13 ± 0.18, healthy group = 1.02 ± 0.11; t34 = -2.46, P = .04) than the healthy control group.. Asymmetries in measures of quadriceps function and cortical excitability were present in patients with ACLR. Asymmetry in quadriceps strength, activation, and cortical excitability persisted in individuals with ACLR beyond return to recreational activity. Measuring the magnitude of asymmetry after ACLR represents an important step in understanding long-term reductions in self-reported function and increased rate of subsequent joint injury in otherwise healthy, active individuals after ACLR.

Topics: Adolescent; Adult; Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Anterior Cruciate Ligament Reconstruction; Athletic Injuries; Female; Humans; Isometric Contraction; Knee Joint; Male; Muscle Weakness; Postoperative Complications; Psychomotor Performance; Quadriceps Muscle; Torque

Muscular weakness is a frequent cause of instability that contributes to falls in Parkinson's disease (PD). Isokinetic dynamometry is a method of muscle assessment useful to measure the muscular strength giving a quantification of the weakness, but only few studies about isokinetic assessment were performed in PD. The aims of the study were to evaluate the muscle strength in PD and to investigate the differences in patients affected on the right and left side.. Knee flexor and extensor muscles strength was assessed using an isokinetic dynamometer in 25 patients in stage 3 H&Y and in 15 healthy controls. Subjects were tested in both legs at three fixed angular velocities: 90°/s, 120°/s, 180°/s.. Considering the whole population of Parkinsonians, no difference in strength was observed with respect to controls. Considering the side, patients affected on the right side showed a clear tendency to be weaker than patients affected on the left side and controls.. PD patients affected on the right side, but not those affected on the left side, had a reduction in muscle strength as compared to controls. We postulate a central origin deficit in muscle strength in PD. It is known that dopamine transporter binding is more severely reduced in the left posterior putamen and our results suggest that the control of the muscle strength in PD is linked to the right-left hemispheric asymmetry of the functional organization of basal ganglia and with their connections to cortical motor and pre-motor areas.

Topics: Aged; Female; Functional Laterality; Humans; Knee; Male; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Parkinson Disease; Torque

After an anterior cruciate ligament (ACL) injury, the uninjured contralateral lower limb may become weakened because of neuromuscular changes, proprioceptive deficits, and disuse of the limb; this weakness predisposes the limb to ACL injury. However, no results have been reported regarding weakness in the contralateral limb after ACL injury.. Muscle strength and functional status of the contralateral lower limb are reduced after unilateral ACL injury.. Cohort study; Level of evidence, 3.. The ACL group consisted of 75 patients who underwent primary unilateral ACL reconstruction and were followed at 3, 6, 12, and 24 months postoperatively. A group of 75 healthy individuals (controls) were matched one-to-one with the ACL group for age, sex, body mass index, and initial Tegner activity level. The side that was evaluated in each control subject corresponded to the injured limb in the matched ACL subject. Isokinetic muscle strength, including extension peak torque per body weight (EPT) and flexion peak torque per body weight (FPT), was evaluated at angular velocities of 60 and 180 deg/s. Patients were also evaluated by single-legged hop test.. Compared with the EPT at 60 deg/s in the control group (290.9 ± 40.1 N · m/kg), the value in the ACL group 24-month follow-up (276.6 ± 42.8 N · m/kg) as well as other follow-up times was significantly lower (P < .05), whereas the EPT at 180 deg/s and the FPT at 60 and 180 deg/s in the ACL group were significantly lower than the control group at 3-month follow-up but were restored to normal levels at final follow-up. Results from the single-legged hop test demonstrated that the ACL group performed at a significantly lower level than the control group at 24-month follow-up (158.4 ± 25.3 vs 176.3 ± 24.7 cm; P < .05) as well as other follow-up times. However, both measurements improved significantly as the follow-up time progressed.. After ACL injury, isokinetic extensor muscle strength and functional status of the contralateral limb were reduced, even at 24 months after ACL reconstruction. However, both measurements improved significantly as the follow-up time progressed. In contrast, flexion muscle strength was restored to normal levels. Therefore, care should be taken to restore muscle strength and functional status in not only the ACL-reconstructed knee but also the uninjured limb.

Topics: Adult; Anterior Cruciate Ligament Injuries; Anterior Cruciate Ligament Reconstruction; Female; Follow-Up Studies; Humans; Knee Injuries; Lower Extremity; Lysholm Knee Score; Male; Muscle Strength; Muscle Weakness; Range of Motion, Articular; Torque; Young Adult

Muscle weakness is present in the paretic limbs of individuals with cerebral palsy (CP). We aimed to determine what neuromuscular factors contribute to weakness in adults with CP during isometric maximal voluntary contractions (iMVCs).. Gastrocnemius anatomical cross-sectional area (ACSA) and agonist and antagonist activation were measured in 11 CP and 11 control adult men during plantarflexion iMVC.. Plantarflexion iMVC torque of the paretic leg was 42% and 52% less than in the non-paretic and control limbs, respectively. The paretic gastrocnemius ACSA was smaller than in the control group only. Paretic agonist activation was less than the non-paretic and control groups, whereas antagonist coactivation was higher. Multiple regression analysis revealed muscle activation accounted for 57% of variation in paretic plantarflexion iMVC torque.. In individuals with CP, muscle weakness in the paretic limb is attributed primarily to impaired neural activation and, to a lesser degree, ACSA.

Topics: Biomechanical Phenomena; Case-Control Studies; Cerebral Palsy; Electromyography; Humans; Isometric Contraction; Male; Muscle Contraction; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Regression Analysis; Torque; Young Adult

Whereas deficits in muscle function, particularly power production, develop in old age and are risk factors for mobility impairment, a complete understanding of muscle fatigue during dynamic contractions is lacking. We tested hypotheses related to torque-producing capacity, fatigue resistance, and variability of torque production during repeated maximal contractions in healthy older, mobility-impaired older, and young women.. Knee extensor fatigue (decline in torque) was measured during 4 min of dynamic contractions. Torque variability was characterized using a novel 4-component logistic regression model.. Young women produced more torque at baseline and during the protocol than older women (P < 0.001). Although fatigue did not differ between groups (P = 0.53), torque variability differed by group (P = 0.022) and was greater in older impaired compared with young women (P = 0.010).. These results suggest that increased torque variability may combine with baseline muscle weakness to limit function, particularly in older adults with mobility impairments.

Topics: Adult; Aged; Aged, 80 and over; Aging; Biomechanical Phenomena; Disability Evaluation; Female; Health Status; Humans; Knee Joint; Mobility Limitation; Models, Biological; Muscle Contraction; Muscle Fatigue; Muscle Weakness; Regression Analysis; Torque

Extensive neuromotor development occurs early in human life, and the timing of brain injury may affect the resulting motor impairment. In Part I of this series, it was demonstrated that the distribution of weakness in the upper extremity depended on the timing of brain injury in individuals with childhood-onset hemiparesis.. The goal of this study was to characterize how timing of brain injury affects joint torque synergies, or losses of independent joint control.. Twenty-four individuals with hemiparesis were divided into 3 groups based on the timing of their injury: before birth (PRE-natal, n = 8), around the time of birth (PERI-natal, n = 8), and after 6 months of age (POST-natal, n = 8). Individuals with hemiparesis and 8 typically developing peers participated in maximal isometric shoulder, elbow, wrist, and finger torque generation tasks while their efforts were recorded by a multiple degree-of-freedom load cell. Motor output in 4 joints of the upper extremity was concurrently measured during 8 primary torque generation tasks to quantify joint torque synergies.. There were a number of significant coupling patterns identified in individuals with hemiparesis that differed from the typically developing group. POST-natal differences were most noted in the coupling of shoulder abductors with elbow, wrist, and finger flexors, while the PRE-natal group demonstrated significant distal joint coupling with elbow flexion.. The torque synergies measured provide indirect evidence for the use of bulbospinal pathways in the POST-natal group, while those with earlier injury may use relatively preserved ipsilateral corticospinal motor pathways.

Topics: Adolescent; Adult; Brain Injuries; Child; Elbow Joint; Female; Hand Joints; Humans; Isometric Contraction; Male; Muscle Weakness; Paresis; Shoulder Joint; Torque; Upper Extremity

Osteitis pubis refers to a painful, inflammatory condition involving the pubic bones, pubic symphysis, and adjacent structures. So, the aims of the study were to evaluate the strength of trunk muscles of soccer players suffering from osteitis pubis, and to compare the agonist/antagonist ratio of trunk muscles in osteitis pubis athletes with that of healthy athletes.. Twenty-five soccer male athletes with osteitis pubis, and 25 healthy soccer athletes. Peak torque/body weight (PT/BW) was recorded from trunk muscles during isokinetic concentric and eccentric contraction modes at a speed of 120°/s for healthy and osteitis pubis soccer players.. There was a significant decrease in concentric contraction of back muscles in osteitis pubis group (p=0.01). A significant decrease in eccentric contraction of abdominal muscles was also recorded in osteitis pubis group (p=0.008). Concentric abdominal/back muscles ratio was significantly higher in osteitis pubis group (p=0.016), with no significant difference in eccentric abdominal/back muscles ratio between both groups (p>0.05).. Osteitis pubis group displayed concentric weakness of back muscle and eccentric weakness of abdominal muscles that lead to disturbance of the normal concentric abdominal/back ratio.

Topics: Abdominal Muscles; Adolescent; Athletes; Athletic Injuries; Back Muscles; Biomechanical Phenomena; Humans; Male; Muscle Contraction; Muscle Weakness; Osteitis; Pubic Bone; Pubic Symphysis; Soccer; Torque; Torso; Young Adult

Extensive neuromotor development occurs early in human life, but the time that a brain injury occurs during development has not been rigorously studied when quantifying motor impairments.. This study investigated the impact of timing of brain injury on the magnitude and distribution of weakness in the paretic arm of individuals with childhood-onset hemiparesis.. A total of 24 individuals with hemiparesis were divided into time periods of injury before birth (PRE-natal, n = 8), around the time of birth (PERI-natal, n = 8), or after 6 months of age (POST-natal, n = 8). They, along with 8 typically developing peers, participated in maximal isometric shoulder, elbow, wrist, and finger torque generation tasks using a multiple-degree-of-freedom load cell to quantify torques in 10 directions. A mixed-model ANOVA was used to determine the effect of group and task on a calculated relative weakness ratio between arms.. There was a significant effect of both time of injury group (P < .001) and joint torque direction (P < .001) on the relative weakness of the paretic arm. Distal joints were more affected compared with proximal joints, especially in the POST-natal group.. The distribution of weakness provides evidence for the relative preservation of ipsilateral corticospinal motor pathways to the paretic limb in those individuals injured earlier, whereas those who sustained later injury may rely more on indirect ipsilateral corticobulbospinal projections during the generation of torques with the paretic arm.

Topics: Adolescent; Adult; Age Factors; Brain Injuries; Child; Electromyography; Female; Humans; Isometric Contraction; Male; Muscle Fatigue; Muscle Weakness; Paresis; Torque; Upper Extremity

The aim of this exploratory study was to verify whether the evaluation of quadriceps muscle weakness is influenced by the testing modality (isometric vs. isokinetic vs. isoinertial) and by the calculation method (within-subject vs. between-subject comparisons) in patients 4-8months after total knee arthroplasty (TKA, n=29) and total hip arthroplasty (THA, n=30), and in healthy controls (n=19). Maximal quadriceps strength was evaluated as (1) the maximal voluntary contraction (MVC) torque during an isometric contraction, (2) the peak torque during an isokinetic contraction, and (3) the one repetition maximum (1-RM) load during an isoinertial contraction. Muscle weakness was calculated as the difference between the involved and the uninvolved side (within-subject comparison) and as the difference between the involved side of patients and controls (between-subject comparison). Muscle weakness estimates were not significantly affected by the calculation method (within-subject vs. between-subject; P>0.05), whereas a significant main effect of testing modality (P<0.05) was observed. Isometric MVC torque provided smaller weakness estimates than isokinetic peak torque (P=0.06) and isoinertial 1-RM load (P=0.008), and the clinical occurrence of weakness (proportion of patients with large strength deficits) was also lower for MVC torque. These results have important implications for the evaluation of quadriceps muscle weakness in TKA and THA patients 4-8months after surgery.

Topics: Aged; Arthroplasty, Replacement, Hip; Arthroplasty, Replacement, Knee; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Quadriceps Muscle; Reproducibility of Results; Torque

The aim of this study was to determine whether declines in knee flexor strength following overground repeat sprints were related to changes in hamstrings myoelectrical activity. Seventeen recreationally active men completed maximal isokinetic concentric and eccentric knee flexor strength assessments at 180°/s before and after repeat sprint running. Myoelectrical activity of the biceps femoris (BF) and medial hamstrings (MHs) was measured during all isokinetic contractions. Repeated measures mixed model [fixed factors = time (pre- and post-repeat sprint) and leg (dominant and nondominant), random factor = participants] design was fitted with the restricted maximal likelihood method. Repeat sprint running resulted in significant declines in eccentric, and concentric, knee flexor strength (eccentric = 26 ± 4 Nm, 15% P < 0.001; concentric 11 ± 2 Nm, 10% P < 0.001). Eccentric BF myoelectrical activity was significantly reduced (10%; P = 0.035). Concentric BF and all MH myoelectrical activity were not altered. The declines in maximal eccentric torque were associated with the change in eccentric BF myoelectrical activity (P = 0.013). Following repeat sprint running, there were preferential declines in the myoelectrical activity of the BF, which explained declines in eccentric knee flexor strength.

Topics: Adult; Electromyography; Exercise Test; Humans; Male; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Random Allocation; Running; Thigh; Torque; Young Adult

Ehlers-Danlos syndrome (EDS), a connective tissue disorder, may lead to impaired contractile function of lower limb muscles.. To test this hypothesis and to understand the possible mechanisms involved, isometric function of the thigh muscles was investigated at different joint angles (30°, 60°, and 90° of knee flexion) in 7 tenascin-X (TNX)-deficient EDS patients.. There was reduced maximal voluntary torque of the knee extensors (but not knee flexors) across all joint angles in the patients. Time to reach maximal rate of torque development was delayed, and voluntary activation capacity was reduced in patients compared with controls, particularly at 30°.. EDS is associated with muscle weakness, most likely due to increased compliance of the series-elastic component of muscle tissue and failure of maximal voluntary muscle activation. Further research is required to understand the influence of reduced voluntary activation on the severe fatigue reported by EDS patients.

Topics: Adult; Ehlers-Danlos Syndrome; Female; Humans; Knee; Knee Joint; Male; Middle Aged; Motor Activity; Muscle Contraction; Muscle Weakness; Quadriceps Muscle; Thigh; Torque

Spasticity and reduced strength are both primary neuromuscular impairments associated with cerebral palsy (CP). However, it is unclear whether spasticity or reduced strength is the strongest contributor to activity limitations.. To study whether involuntary activation of the biceps brachii muscle, in addition to reduced strength, contributes to limitations in upper limb activity in children with CP.. Fifteen children with unilateral CP (9 males and 6 females, age range 8-17 years) participated in this study. Involuntary activation, reflecting spasticity, was studied as biceps brachii activity during passive elbow extension at four isokinetic velocities (10, 90, 180 and 300°/s). Elbow flexion peak torque, reflecting strength, was measured during maximal voluntary isometric contraction, and concurrent biceps brachii activity was registered reflecting voluntary muscle activation. Bimanual upper limb activity was assessed in the performance domain using the Assisting Hand Assessment (AHA).. Both involuntary and voluntary muscle activation were related to activity, the former negatively, but voluntary activation showed the strongest relationship (Spearmans rho = .84). Involuntary muscle activation at 10, 90 and 180°/s was negatively related to muscle strength (Spearmans rho = -.63, -.58 and -.62, respectively).. Our results do not indicate that spasticity affects upper limb activity in addition to strength. Most likely, muscle weakness and spasticity jointly contribute to activity limitations, reflected by the strong relationship between the ability to voluntarily activate a muscle and activity performance.

Topics: Adolescent; Cerebral Palsy; Child; Elbow; Electromyography; Female; Humans; Isometric Contraction; Male; Muscle Spasticity; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Torque; Upper Extremity

People with Parkinson disease (PD) typically have complaints of weakness. The mechanisms underlying this deficit have not been well established, although many factors may contribute.. This investigation aimed to characterize quadriceps muscle weakness and activation failure in people with PD and explore whether these deficits were related to disease severity. The authors further sought to examine quadriceps muscle fatigability.. This was a cross-sectional comparison of 17 people with mild-severe PD and 17 healthy adults matched by age, sex, and body mass index (BMI). The Unified Parkinson's Disease Rating Scale motor score (UPDRS motor) ranged from 9.5 to 61.0. Participants were divided into those with low-PD motor signs (UPDRS motor < 31.7) and high-PD motor signs (UPDRS motor ≥ 31.7). Measures of quadriceps performance included isometric torque, central activation using doublet interpolation, and an isokinetic fatigue test.. Participants with high-PD motor signs had significantly more quadriceps weakness and central activation deficits than those with low-PD motor signs or healthy controls. Strength and activation deficits correlated strongly with UPDRS motor score. Quadriceps muscle fatigue was present in healthy controls and in those with low-PD motor signs but not in those with high-PD motor signs.. These findings provide additional evidence for lower-extremity strength loss with PD; central activation deficits may account for some of the strength deficits, especially with increased PD motor signs. Also, muscle fatigue did not occur in individuals with a greater degree of PD motor signs, most likely because of insufficient central activation to allow for muscle overload to induce metabolic fatigue.

Topics: Adult; Aged; Analysis of Variance; Cross-Sectional Studies; Fatigue; Female; Humans; Male; Middle Aged; Muscle Weakness; Parkinson Disease; Psychomotor Disorders; Quadriceps Muscle; Severity of Illness Index; Torque

To examine the relationship between knee osteoarthritis (OA) and muscle parameters in a biracial cohort of older adults.. Participants in the Health, Aging and Body Composition Study (n = 858) were included in this cross-sectional analysis. Computed tomography was used to measure muscle area, and quadriceps strength was measured isokinetically. Muscle quality (specific torque) was defined as strength per unit of muscle area for both the entire thigh and quadriceps. Knee OA was assessed based on radiographic features and knee pain. We compared muscle parameters between those with and without radiographic knee OA (+RKOA group and -RKOA group, respectively) and among 4 groups defined by +RKOA and -RKOA with and without pain.. The mean ± SD age was 73.5 ± 2.9 years and the mean ± SD body mass index (BMI) was 27.9 ± 4.8 kg/m(2) . Fifty-eight percent of participants were women and 44% were African American. Compared to the -RKOA participants, +RKOA participants had a higher BMI (30.2 versus 26.8 kg/m(2)), larger thigh muscles (117.9 versus 108.9 cm(2)), and a greater amount of intermuscular fat (12.5 versus 9.9 cm(2) ; all P < 0.0001). In adjusted models, the +RKOA participants had significantly lower specific torque (P < 0.001), indicating poorer muscle quality, than -RKOA participants, but there was no difference between groups in quadriceps specific torque. The +RKOA without pain (P < 0.05) and the +RKOA with pain (P < 0.001) participants had lower specific torque compared to the -RKOA without pain group. There were no significant differences in quadriceps specific torque among groups.. Muscle quality was significantly poorer in participants with RKOA regardless of pain status. Future studies should address how lifestyle interventions might affect muscle quality and progression of knee OA.

Topics: Adiposity; Age Factors; Aged; Analysis of Variance; Arthralgia; Biomechanical Phenomena; Black or African American; Body Mass Index; Case-Control Studies; Cross-Sectional Studies; Disease Progression; Female; Humans; Linear Models; Male; Muscle Strength; Muscle Weakness; Organ Size; Osteoarthritis, Knee; Pain Measurement; Pennsylvania; Quadriceps Muscle; Risk Assessment; Risk Factors; Sex Factors; Tennessee; Tomography, X-Ray Computed; Torque; White People

This study was conducted to identify factors other than morphological muscle strength factors that affect injured and uninjured sides of knee flexors with anterior cruciate ligament (ACL) lesions.. The study population consisted of 22 patients with ACL lesions. Their hamstring muscle volume was measured on MRI, and muscle torque per muscle volume was calculated as the peak torque of knee flexion divided by hamstring muscle volume.. The mean muscle torque per unit volume of hamstrings in patients with ACL rupture was 0.09 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.01 Nm/cm(3) at 180°/s on the injured side, and 0.11 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.01 Nm/cm(3) at 180°/s on the uninjured side. The mean muscle torque per unit volume of hamstrings in control subjects was 0.11 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.03 Nm/cm(3) at 180°/s. One-factor ANOVA analysis found no significant differences between the three groups at either flexion velocity.. Neurological dysfunction does not appear to exist in knee flexor muscles after ACL injury, unlike the quadriceps. Since the mechanism of muscle weakness will differ depending on the muscle, it is important for clinicians to take this discrepancy into consideration.. II.

Topics: Adult; Analysis of Variance; Anterior Cruciate Ligament Injuries; Case-Control Studies; Female; Humans; Knee Injuries; Magnetic Resonance Imaging; Male; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Torque

Unilateral posterior crossbite (UPCB) is characterised by an inverse relationship of the upper and lower buccal dental cusps and may involve one or several teeth. The aim of this study was to compare the electromyographic outcomes of patients with UPCB and those of healthy controls.. Fifteen patients (mean age 11.5 years) with UPCB and fifteen healthy controls (mean age 12 years) were examined at the Department of Orthodontics, Second University of Naples. Surface electromyography was performed on patients and controls.. Patients with UPCB had less muscle activation than healthy subjects (p<0.0001) and an asymmetric muscle activation with 89.23% muscle balancing for temporals and 83.21% for masseters. The control group showed a 99.32% of muscle balancing for temporals and 97.77% for masseters. These findings suggest that asymmetric muscle activation may influence maxillary and mandibular growth in adolescents with UPCB.

Topics: Adolescent; Analog-Digital Conversion; Child; Electromyography; Female; Humans; Male; Malocclusion; Masseter Muscle; Muscle Contraction; Muscle Weakness; Temporal Muscle; Torque

To compare the ankle muscle strength and torque-angle relationship between individuals with Parkinson's disease (PD) and participants without impairments.. Cross-sectional, exploratory study.. Motor control laboratory in a university.. Convenience sample of community-dwelling individuals with PD (n=59) recruited from a PD self-help group and age-matched participants without impairments (n=37) recruited from community older adult centers.. Not applicable.. Peak torque and angle-torque profile during concentric and eccentric contraction of ankle dorsiflexors and plantarflexors at 2 different angular speeds (45 and 90°/s).. The PD group displayed lower muscle peak torque values than participants without impairments in all test conditions. Generally, concentric strength was more compromised, with a greater between-group difference (Cohen d=1.29-1.60) than eccentric strength (Cohen d=.81-1.37). Significant group by angular speed interaction was observed in ankle plantarflexion concentric peak torque (P<.001), indicating that muscle weakness was more pronounced when the angular speed was increased. The group by joint angle interaction in concentric contraction of ankle plantarflexors at 90°/s was also significant (P<.001), revealing that the between-group difference in torque values became increasingly more pronounced when the joint was moving toward the end range of the ankle plantarflexion. This exaggerated ankle plantarflexor muscle weakness at the end range was significantly correlated with clinical balance measures (P<.05).. Muscle weakness in PD is influenced by contraction type, angular speed, and joint range. Exaggerated weakness is found in concentric contraction of ankle plantarflexors, particularly when the angular speed is high and the muscle is in shortened lengths.

Topics: Aged; Ankle; Biomechanical Phenomena; Cross-Sectional Studies; Humans; Middle Aged; Muscle Contraction; Muscle Strength; Muscle Weakness; Parkinson Disease; Range of Motion, Articular; Torque

The purpose of this study was to obtain evidence to support the hypothesis that motor unit recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture.. We compared muscle torque per unit volume in the QF from injured and uninjured sides to normal subjects. If high-threshold motor unit recruitment is reduced in patients with ACL rupture, this reduction will theoretically lead to a reduction in muscle torque per unit volume compared to the control group. The subjects included 22 patients with ACL rupture and 22 subjects with no history of knee injury. To identify the muscle torque per unit volume, the isokinetic peak torque was divided by QF volume which was obtained by MRI.. Tests revealed that the mean muscle torque per unit volume of the uninjured and injured sides was significantly lower than those of the control group.. This study demonstrated that the values of the muscle torque per unit volume of both injured and uninjured sides of patients with ACL rupture were significantly lower than those of the control group, thereby providing indirect evidence of the hindrance of motor unit recruitment in these patients. The results of the present study also indicate that there may be bilateral QF weakness in patients with ACL rupture. Since persistent QF weakness is a significant barrier to effective rehabilitation in patients with ACL injuries, a better understanding of the underlying mechanisms will allow clinicians and scientists to develop more effective therapeutic strategies for patient rehabilitation.

Topics: Adult; Analysis of Variance; Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Case-Control Studies; Female; Humans; Injury Severity Score; Knee Injuries; Magnetic Resonance Imaging; Male; Muscle Contraction; Muscle Weakness; Organ Size; Physical Examination; Quadriceps Muscle; Reference Values; Rupture; Torque; Young Adult

A consequence of knee joint osteoarthritis (OA) is an inability to fully activate the quadriceps muscles, a problem termed arthrogenic muscle inhibition (AMI). AMI leads to marked quadriceps weakness that impairs physical function and may hasten disease progression. The purpose of the present study was to determine whether γ-loop dysfunction contributes to AMI in people with knee joint OA.. Fifteen subjects with knee joint OA and 15 controls with no history of knee joint pathology participated in this study. Quadriceps and hamstrings peak isometric torque (Nm) and electromyography (EMG) amplitude were collected before and after 20 minutes of 50 Hz vibration applied to the infrapatellar tendon. Between-group differences in pre-vibration torque were analysed using a one-way analysis of covariance, with age, gender and body mass (kg) as the covariates. If the γ-loop is intact, vibration should decrease torque and EMG levels in the target muscle; if dysfunctional, then torque and EMG levels should not change following vibration. One-sample t tests were thus undertaken to analyse whether percentage changes in torque and EMG differed from zero after vibration in each group. In addition, analyses of covariance were utilised to analyse between-group differences in the percentage changes in torque and EMG following vibration.. Pre-vibration quadriceps torque was significantly lower in the OA group compared with the control group (P = 0.005). Following tendon vibration, quadriceps torque (P < 0.001) and EMG amplitude (P ≤0.001) decreased significantly in the control group but did not change in the OA group (all P > 0.299). Hamstrings torque and EMG amplitude were unchanged in both groups (all P > 0.204). The vibration-induced changes in quadriceps torque and EMG were significantly different between the OA and control groups (all P < 0.011). No between-group differences were observed for the change in hamstrings torque or EMG (all P > 0.554).. γ-loop dysfunction may contribute to AMI in individuals with knee joint OA, partially explaining the marked quadriceps weakness and atrophy that is often observed in this population.

Topics: Aged; Biomechanical Phenomena; Electromyography; Female; Humans; Knee Joint; Male; Middle Aged; Muscle Weakness; Osteoarthritis, Knee; Quadriceps Muscle; Torque; Vibration

Aging is commonly associated with a loss of muscle mass and strength, resulting in falls, functional decline, and the subjective feeling of weakness. Exercise modulates the morbidities of muscle aging. Most studies, however, have examined muscle-loss changes in sedentary aging adults. This leaves the question of whether the changes that are commonly associated with muscle aging reflect the true physiology of muscle aging or whether they reflect disuse atrophy. This study evaluated whether high levels of chronic exercise prevents the loss of lean muscle mass and strength experienced in sedentary aging adults. A cross-section of 40 high-level recreational athletes ("masters athletes") who were aged 40 to 81 years and trained 4 to 5 times per week underwent tests of health/activity, body composition, quadriceps peak torque (PT), and magnetic resonance imaging of bilateral quadriceps. Mid-thigh muscle area, quadriceps area (QA), subcutaneous adipose tissue, and intramuscular adipose tissue were quantified in magnetic resonance imaging using medical image processing, analysis, and visualization software. One-way analysis of variance was used to examine age group differences. Relationships were evaluated using Spearman correlations. Mid-thigh muscle area (P = 0.31) and lean mass (P = 0.15) did not increase with age and were significantly related to retention of mid-thigh muscle area (P < 0.0001). This occurred despite an increase in total body fat percentage (P = 0.003) with age. Mid-thigh muscle area (P = 0.12), QA (P = 0.17), and quadriceps PT did not decline with age. Specific strength (strength per QA) did not decline significantly with age (P = 0.06). As muscle area increased, PT increased significantly (P = 0.008). There was not a significant relationship between intramuscular adipose tissue (P = 0.71) or lean mass (P = 0.4) and PT. This study contradicts the common observation that muscle mass and strength decline as a function of aging alone. Instead, these declines may signal the effect of chronic disuse rather than muscle aging. Evaluation of masters athletes removes disuse as a confounding variable in the study of lower-extremity function and loss of lean muscle mass. This maintenance of muscle mass and strength may decrease or eliminate the falls, functional decline, and loss of independence that are commonly seen in aging adults.

Topics: Adult; Aged; Aged, 80 and over; Analysis of Variance; Athletes; Body Composition; Cross-Sectional Studies; Exercise; Female; Humans; Leg; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Torque

The muscle torque per unit volume of the hamstrings on the injured and uninjured sides in patients with ACL reconstruction were compared with participants with no history of knee injury to examine whether a similar mechanism leading to quadriceps weakness exists in the hamstrings of these patients. The study population consisted of 18 and 52 patients at

Topics: Adolescent; Adult; Analysis of Variance; Anterior Cruciate Ligament; Case-Control Studies; Female; Humans; Knee Injuries; Knee Joint; Magnetic Resonance Imaging; Male; Muscle Strength; Muscle Weakness; Quadriceps Muscle; Radiography; Thigh; Torque; Young Adult

In clinically diagnosed rheumatoid arthritis (RA), studies were conducted to investigate the reflex and passive tissue contribution to measured increases in joint stiffness in the resting upper limb and during constant contractions of an attached muscle. The tonic stretch reflex was induced by a servo-controlled sinusoidal stretch perturbation of the metacarpophalangeal joint of RA patients, and age- and sex-matched controls. The resulting reflexes and mechanical changes in the RA affected joint were explored. Surface electromyographic (EMG) measurements were obtained from first dorsal interosseus muscle. Reflex gain (EMG/joint angle amplitude ratio), phase difference (reflex delay after stretch), coherence square (proportion of EMG variance accounted for by joint angle changes), joint mechanical gain (torque-joint angle amplitude ratio) and mechanical phase difference (torque response delay after stretch) were determined. RA patients showed decreased reflex gain that was partly due to coexistent severe muscle weakness, as determined from maximum voluntary contraction and grip pressure estimates. The decreased reflex gain was most evident at high stretch frequency suggesting a disproportionate loss of the large diameter afferent response and also increased reflex delay in the patients. These changes ensemble suggest significant loss of neural drive to the motor unit population. Patients also showed increased joint stiffness (measured as torque gain) in the contracting muscle, but there was no evidence of reflex activity or increased stiffness at rest. This suggests that the increased joint stiffness in RA was due to changes in the mechanical properties of the active muscle-joint system rather than changes in reflex properties.

Topics: Adult; Arthritis, Rheumatoid; Biomechanical Phenomena; Electromyography; Female; Fingers; Humans; Joints; Male; Metacarpophalangeal Joint; Middle Aged; Motor Neurons; Muscle Contraction; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Nerve Fibers, Myelinated; Range of Motion, Articular; Reflex, Stretch; Torque

To compare the strength of the hip musculature in people with symptomatic medial knee osteoarthritis (OA) with asymptomatic controls.. Eighty-nine people with knee OA and 23 controls age >50 years were recruited from the community. The maximal isometric strength (torque relative to body mass) of the hip abductors, adductors, flexors, extensors, and internal and external rotators was evaluated using hand-held dynamometry or a customized force transducer apparatus. Univariate linear models with age and sex included as covariates were used to compare muscle strength between groups.. In people with knee OA, significant strength deficits were evident for all hip muscle groups evaluated (P < 0.05). Compared with controls, strength deficits ranged from 16% (hip extensors) to 27% (hip external rotators) after accounting for differences in sex and age between groups.. People with knee OA demonstrate significant weakness of the hip musculature compared with asymptomatic controls. It is not clear if hip muscle weakness precedes the onset of knee OA or occurs as a consequence of disease. Findings from this study support the inclusion of hip strengthening exercises in rehabilitation programs.

Topics: Aged; Case-Control Studies; Exercise; Exercise Therapy; Female; Hip; Humans; Male; Middle Aged; Muscle Strength; Muscle Weakness; Osteoarthritis, Knee; Pain; Torque

The aim of this study was to examine the repeatability of and relationships among spasticity, co-contraction of agonist-antagonist, and muscle strength in children with cerebral palsy (CP). Eight children with spastic diplegic CP (five males, three females; Gross Motor Function Classification System [GMFCS] Levels I-III; mean age 10y 2mo [SD 2y 9mo], range 6-13y) and nine children in a comparison group (six males, three females; mean age 8y 10mo [SD 2y 4mo], range 6y to 12y 6mo) were assessed twice to examine repeatability of Composite Spasticity Scale, soleus stretch reflexes, electromyography (EMG) co-contraction ratio, and torque recorded during maximal isometric voluntary contraction of ankle dorsiflexors and plantarflexors. Sixty-one children with spastic CP, (54 diplegic, seven hemiplegic; 32 males, 29 females; GMFCS levels I-III; mean age 10y 8mo [SD 2y 9mo], range 6-15y) were then assessed to delineate possible correlations among these measures. Intraclass correlation coefficients (0.78-0.97) showed high data repeatability in both groups. Children with spastic CP demonstrated significantly larger soleus stretch reflex/M-response areas smaller torques, but larger EMG co-contraction ratios during both voluntary dorsiflexion and plantarflexion (all p<0.05). Children with spastic CP who had larger soleus stretch reflex/M-response areas demonstrated larger plantarflexion co-contraction ratio (r = 0.28), and produced smaller plantarflexion and dorsiflexion torques (r = -0.48 and -0.27 respectively). However, no correlation was noted between soleus stretch reflex and clinical spasticity. Our findings demonstrated that hyperactive soleus stretch reflex affected torque production of ankle muscles. Moreover, the severity of spasticity may not be fully described by either stretch reflex or tone measure alone.

Topics: Adolescent; Cerebral Palsy; Child; Electromyography; Female; Humans; Male; Muscle Contraction; Muscle Spasticity; Muscle Weakness; Muscle, Skeletal; Reflex, Stretch; Reproducibility of Results; Statistics as Topic; Torque

Sensorimotor deficits such as impaired joint proprioception and muscle weakness have been found in association with hypermobility syndrome (HMS) in adults. HMS is more common in children than adults, yet such deficits have not been adequately investigated in paediatric populations. It is therefore uncertain as to what sensorimotor deficits are present in children with HMS. This study investigated knee joint proprioception and muscle torque in healthy children and those with HMS.. Thirty-seven healthy children (mean age +/- s.d. = 11.5 +/- 2.6 yrs) and 29 children with HMS (mean age +/- s.d. = 11.9 +/- 1.8 yrs) participated in this study. Knee joint kinaesthesia (JK) and joint position sense (JPS) were measured, with the absolute angular error (AAE) calculated as the absolute difference between the target and perceived angles. Knee extensor and flexor muscle torque was assessed and normalized to body mass. Mann-Whitney U-tests were performed to compare JK, JPS and muscle torque between the two groups.. Children with HMS had significantly poorer JK and JPS compared with the controls (both P < 0.001). Knee extensor and flexor muscle torque was also significantly reduced (both P < 0.001) in children with HMS compared with their healthy counterparts.. The findings of this study demonstrated that knee joint proprioception was impaired in children with HMS. They also had weaker knee extensor and flexor muscles than healthy controls. Clinicians should be aware of these identified deficits in children with HMS, and a programme of proprioceptive training and muscle strengthening may be indicated.

Topics: Adolescent; Case-Control Studies; Child; Female; Humans; Joint Instability; Knee Joint; Male; Muscle Weakness; Muscle, Skeletal; Proprioception; Range of Motion, Articular; Statistics, Nonparametric; Torque

There is evidence to suggest that contractile properties of muscles in people with multiple sclerosis change as a consequence of demyelination in central nervous system. However, passive properties of muscles in people with multiple sclerosis have not been previously investigated. The purpose of this study was to characterise passive mechanical properties of gastrocnemius in people with multiple sclerosis and to compare these properties with those of gastrocnemius in neurologically normal people.. Ten people with multiple sclerosis having signs and symptoms of weakness in the legs (Disease step 1-3) and 10 age- and sex-matched healthy people participated in the study. Ultrasound images of muscle fascicles of medial gastrocnemius as well as passive ankle torque and ankle angle data were obtained simultaneously as the ankle was rotated through its full range with the knee in a range of positions. Analysis of ultrasound images and passive ankle torque-angle relations allowed us to derive the slack lengths and maximal strains of whole muscle-tendon units, muscle fascicles and tendons. Paired-samples t-tests were used to compare these variables in the two groups.. There was no difference between subjects with multiple sclerosis and healthy controls in the mean slack lengths and mean maximal strains of the whole muscle-tendon units or of their fascicles or tendons.. These data suggests that typically, in people with multiple sclerosis who have impaired lower limbs but are still ambulatory, the passive mechanical properties of the gastrocnemius muscles are normal.

Topics: Adult; Case-Control Studies; Central Nervous System; Equipment Design; Female; Humans; Male; Middle Aged; Multiple Sclerosis; Muscle Weakness; Muscle, Skeletal; Myelin Sheath; Stress, Mechanical; Tendons; Torque

despite evidence of an obesity-related disability, there is a lack of objective muscle functional data in overweight subjects. Only few studies provide instrumental strength measurements in non-syndromal obesity, whereas no data about Prader-Willi syndrome (PWS) are reported. The aim of our study was to characterize the lower limb muscle function of patients affected by PWS as compared to non-syndromal obesity and normal-weight subjects.. We enrolled 20 obese (O) females (age: 29.1 +/- 6.5 years; BMI: 38.1 +/- 3.1), 6 PWS females (age: 27.2 +/- 4.9 years; BMI: 45.8 +/- 4.4) and 14 healthy normal-weight (H) females (age: 30.1 +/- 4.7 years; BMI: 21 +/- 1.6). Isokinetic strength during knee flexion and extension in both lower limbs at the fixed angular velocities of 60 degrees /s, 180 degrees /s, 240 degrees /s was measured with a Cybex Norm dynamometer.. the H, O and PWS populations appear to be clearly stratified with regard to muscle strength.: PWS showed the lowest absolute peak torque (PT) for knee flexor and extensor muscles as compared to O (-55%) and H (-47%) (P = 0.00001). O showed significantly higher strength values than H as regard to knee extension only (P = 0.0014). When strength data were normalised by body weight, PWS showed a 50% and a 70% reduction in PT as compared to O and H, respectively. Knee flexors strength values were on average half of those reported for extension in all of the three populations.. the novel aspect of our study is the determination of objective measures of muscle strength in PWS and the comparison with O and H patients. The objective characterization of muscle function performed in this study provides baseline and outcome measures that may quantify specific strength deficits amendable with tailored rehabilitation programs and monitor effectiveness of treatments.

Topics: Adult; Causality; Exercise Therapy; Exercise Tolerance; Female; Gait Disorders, Neurologic; Humans; Knee; Movement; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Obesity; Physical Fitness; Prader-Willi Syndrome; Quadriceps Muscle; Range of Motion, Articular; Resistance Training; Torque; Young Adult

Patellofemoral pain (PFP) is thought to be related to patellar maltracking due to imbalances in the knee extensor. However, no study has evaluated the in vivo biomechanical properties of the quadriceps tendon in PFP syndrome. Our purpose was to compare the biomechanical properties of the quadriceps tendons in vivo and noninvasively in patients with PFP syndrome to those of control subjects. The null hypothesis was that the quadriceps tendons of PFP subjects would have significantly decreased strain compared with control subjects. Fourteen subjects (7 control, 7 PFP) performed voluntary ramp isometric contractions to a range of torque levels, while quadriceps tendon elongation was measured using ultrasonography. Tendon strain was calculated for the vastus medialis obliquus (VMO) and vastus lateralis (VL) portion of the quadriceps tendon and compared between subjects (control vs. PFP) and within subjects (VMO vs. VL). PFP subjects showed significantly less VMO tendon strain than control subjects (P<0.001), but there was no difference in VL tendon strain between PFP and control subjects (P=0.100). Relative weakness of the VMO is the most likely cause of the decreased tendon strain seen in subjects with PFP. VMO weakness not only explains the decreased medial tendon strain but also explains the presence of increased lateral patellar translation and lateral patellar spin (distal pole rotates laterally) reported in the literature in this population. This technique can potentially be used in a clinical setting to evaluate quadriceps tendon properties and infer the presence of muscle weakness in PFP.

Topics: Biomechanical Phenomena; Case-Control Studies; Elasticity; Humans; Isometric Contraction; Muscle Strength; Muscle Weakness; Patellar Ligament; Patellofemoral Pain Syndrome; Quadriceps Muscle; Tendon Injuries; Time Factors; Torque; Ultrasonography

Topics: Data Interpretation, Statistical; Electric Stimulation; Humans; Motivation; Motor Activity; Motor Cortex; Motor Neurons; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Reproducibility of Results; Stroke; Torque

Instead of hyper-reflexia as sole paradigm, post-stroke movement disorders are currently considered the result of a complex interplay between neuronal and muscular properties, modified by level of activity. We used a closed loop system identification technique to quantify individual contributors to wrist joint stiffness during an active posture task.. Continuous random torque perturbations applied to the wrist joint by a haptic manipulator had to be resisted maximally. Reflex provoking conditions were applied i.e. additional viscous loads and reduced perturbation signal bandwidth. Linear system identification and neuromuscular modeling were used to separate joint stiffness into the intrinsic resistance of the muscles including co-contraction and the reflex mediated contribution.. Compared to an age and sex matched control group, patients showed an overall 50% drop in intrinsic elasticity while their reflexive contribution did not respond to provoking conditions. Patients showed an increased mechanical stability compared to control subjects.. Post stroke, we found active posture tasking to be dominated by: 1) muscle weakness and 2) lack of reflex adaptation. This adds to existing doubts on reflex blocking therapy as the sole paradigm to improve active task performance and draws attention to muscle strength and power recovery and the role of the inability to modulate reflexes in post stroke movement disorders.

Topics: Adaptation, Physiological; Adult; Aged; Feedback, Physiological; Female; Follow-Up Studies; Humans; Male; Middle Aged; Models, Biological; Muscle Contraction; Muscle Spasticity; Muscle Weakness; Paresis; Posture; Psychomotor Performance; Reflex; Reflex, Abnormal; Stroke; Stroke Rehabilitation; Torque; Weight-Bearing; Wrist Joint

Inactivity is a recognized compounding factor in sarcopenia and muscle weakness in old age. However, while the negative effects of unloading on skeletal muscle in young individuals are well elucidated, only little is known about the consequence of immobilization and the regenerative capacity in elderly individuals. Thus the aim of this study was to examine the effect of aging on changes in muscle contractile properties, specific force, and muscle mass characteristics in 9 old (61-74 yr) and 11 young men (21-27 yr) after 2 wk of immobilization and 4 wk of retraining. Both young and old experienced decreases in maximal muscle strength, resting twitch peak torque and twitch rate of force development, quadriceps muscle volume, pennation angle, and specific force after 2 wk of immobilization (P < 0.05). The decline in quadriceps volume and pennation angle was smaller in old compared with young (P < 0.05). In contrast, only old men experienced a decrease in quadriceps activation. After retraining, both young and old regained their initial muscle strength, but old had smaller gains in quadriceps volume compared with young, and pennation angle increased in young only (P < 0.05). The present study is the first to demonstrate that aging alters the neuromuscular response to short-term disuse and recovery in humans. Notably, immobilization had a greater impact on neuronal motor function in old individuals, while young individuals were more affected at the muscle level. In addition, old individuals showed an attenuated response to retraining after immobilization compared with young individuals.

Topics: Adult; Age Factors; Aged; Aging; Electric Stimulation; Humans; Immobilization; Male; Middle Aged; Motor Neurons; Muscle Contraction; Muscle Strength; Muscle Weakness; Neuromuscular Junction; Organ Size; Physical Therapy Modalities; Quadriceps Muscle; Recovery of Function; Sarcopenia; Time Factors; Torque; Young Adult

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

This study was designed to quantify torque production at different joint angles in the paretic and nonparetic knee joints of individuals with stroke.. Extension and flexion torques were measured at 6 angles of the knee joint and normalized to peak torque in 19 subjects with stroke and 19 controls.. Paretic knee extension torque was lower than controls when the knee was positioned near extension. In contrast, nonparetic knee extension and flexion torques were higher than controls when the knee was positioned near full flexion.. The paretic knee extensors demonstrated exaggerated weakness at short muscle lengths and the nonparetic knee extensors and flexors demonstrated selective strength gains. Clinicians should therefore consider paretic knee extensor strengthening near full extension and promote symmetrical use of the legs to prevent compensatory overuse of the nonparetic leg.

Topics: Adaptation, Physiological; Aged; Arthrometry, Articular; Female; Humans; Knee Joint; Male; Middle Aged; Muscle Weakness; Paresis; Range of Motion, Articular; Stroke; Stroke Rehabilitation; Torque

This study's main purpose was to test the feasibility of employing a non-invasive-stimulated muscle force assessment approach in long-term critically ill patients.. A case series was performed over a 4-year period in the intensive care unit (ICU). Of the 25 patients initially recruited, eight patients required long-time mechanical ventilation for a median of 3.8 weeks (range 2-10 weeks) and were immobilized for 5 weeks (range 2-10 weeks). With a previously tested non-invasive measuring device, we weekly assessed peak torques and rates of force development and relaxation of patients' ankle dorsiflexor contractile responses, induced via peroneal nerve stimulation. Subsequently, we derived each patient's time course of observed progressive weakness and/or recovery.. During their critical illnesses, seven out of eight patients elicited significant decreases in measured peak torques. In survivors (n = 6) during their recovery periods, torques gradually recovered. In the two patients who died, their strengths decreased continuously until death. The rate of force development data elicited similar trends as peak torque responses, whereas relative relaxation rates differed more widely between individuals.. This approach of non-invasive-stimulated muscle force assessment can be used in long-term critically ill patients and may eventually become a standard in the intensive care unit, e.g. for assessing recovery. This method is easy to employ, reproducible, provides important phenotypic quantification of skeletal muscle contractile function, and can be used for long-term outcomes assessment.

Topics: Adult; Aged; Convalescence; Critical Care; Critical Illness; Disease Progression; Electrodiagnosis; Feasibility Studies; Female; Humans; Male; Middle Aged; Muscle Relaxation; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Peroneal Nerve; Polyneuropathies; Positive-Pressure Respiration; Predictive Value of Tests; Torque; Treatment Outcome

It has been previously reported that patients with Parkinson's disease (PD) struggle with fine adjustments of finger forces while manipulating an object. However, impairments in everyday activities can not only be attributed to difficulties with the linear forces applied on an object, but also to the application of rotational forces (torque). This study examined finger strength and isometric torque control in elderly persons with PD. Six individuals with PD (66.1 +/- 0.7 years), six elderly healthy controls (65.3 +/- 0.2 years) matched by age, gender and handedness, and six young adults (22.3 +/- 0.2 years) participated in this study. The subjects were asked to perform two tasks: maximum voluntary thumb-index pinching torque production (MVT) and constant isometric thumb-index torque control at 40% of their MVT for 20 s. The results showed decreased strength and increased difficulty in isometric torque control in individuals with PD as compared to their healthy peers. This study demonstrates that PD affects isometric finger torque production and control.

Topics: Adult; Aged; Aged, 80 and over; Basal Ganglia; Disability Evaluation; Female; Fingers; Hand Strength; Humans; Isometric Contraction; Male; Motor Cortex; Motor Skills; Movement; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Neural Pathways; Parkinson Disease; Predictive Value of Tests; Range of Motion, Articular; Torque

Although spasticity is a common symptom in children with cerebral palsy, weakness may be a much greater contributor to disability. We explore whether a treatment that reduces spasticity may also have potential benefit for improving strength. Ten children with cerebral palsy and spasticity in the ankle plantar flexor muscles were treated with oral baclofen for 4 weeks. We tested voluntary ability to activate ankle plantar flexor muscles using the ratio of the surface electromyographic signal during isometric maximal voluntary contraction to the M-wave during supramaximal electrical stimulation of the tibial nerve and tested muscle strength using maximal isometric plantar flexion torque. Mean maximal voluntary neuromuscular activation increased from 1.13 +/- 1.02 to 1.60 +/- 1.30 ( P < .05) after treatment, corresponding to an increase in 9 of 10 subjects. Mean maximal plantar flexion torque did not change. We conjecture that antispasticity agents could facilitate strength training by increasing the ability to voluntarily activate muscle.

Topics: Administration, Oral; Adolescent; Ankle Joint; Baclofen; Cerebral Palsy; Child; Child, Preschool; Dose-Response Relationship, Drug; Drug Administration Schedule; Electric Stimulation; Electromyography; Female; Follow-Up Studies; H-Reflex; Humans; Isometric Contraction; Male; Muscle Relaxants, Central; Muscle Spasticity; Muscle Strength; Muscle Weakness; Neuromuscular Junction; Range of Motion, Articular; Tibial Nerve; Torque

The objective of this study was to assess the nature of muscle weakness in both legs after stroke compared with able-bodied control individuals and to examine whether there is a relationship between the degree of muscle weakness and coactivation of knee extensors and flexors as well as voluntary activation capacity of knee extensors of both paretic and non-paretic legs and indices of functional performance. Maximal voluntary isometric torques of knee extensors (MVCe) and flexors (MVCf) were determined in 14 patients (bilaterally) and 12 able-bodied controls. Simultaneous measurements were made of torque and surface EMG from agonist and antagonist muscles. Coactivation was calculated. Supramaximal triplets were evoked with electrical stimulation to estimate maximal torque capacity and degree of voluntary activation of knee extensors. MVCs, activation and coactivation parameters were correlated to scores of seven functional performance tests. MVCe, MVCf and voluntary activation were lower in paretic lower limb (PL) compared with both non-paretic lower limb (NL) and control. Besides, all these parameters of NL were also lower than control. Electrically evoked torque capacity of knee extensors of PL was about 60% of both NL and control, which were not significantly different from each other. Strong significant correlations between strength, as well as voluntary activation, and functional performance were found. Coactivation did not correlate well with functional performance. Thus, whereas for NL activation failure can explain weakness, for PL both activation failure and reduced intrinsic torque capacity are responsible for the severe weakness. Activation capacity and muscle strength correlated strongly to functional performance, while coactivation did not.

Topics: Aged; Analysis of Variance; Case-Control Studies; Electromyography; Female; Humans; Knee Joint; Lower Extremity; Male; Middle Aged; Muscle Contraction; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Paresis; Stroke; Torque

Case control study.. To classify individuals with functional ankle instability (FAI) into deficit and non-deficit categories based on the evaluation of the most common factors that have been proposed to be related to FAI.. Recent studies have suggested that FAI may be secondary to a combination of factors including ankle proprioceptive deficit, muscular weakness, impaired balance, delayed neuromuscular reaction time, and joint laxity. However, only a few authors have investigated the prevalence and association among these factors in a single group of individuals.. The above 5 factors were tested bilaterally in 21 individuals with FAI and in 16 healthy control subjects. Data were analyzed for (1) within- and between-group comparison, (2) classification of subjects with FAI into deficit and no-deficit categories, and (3) magnitude of association between factors in the subjects with FAI using Pearson bivariate correlation.. Balance control and evertors' strength were significantly less on the affected side in comparison to the unaffected side in subjects with FAI. The evertors' strength was also significantly different between the side difference of the FAI group and the side difference of the control group. Passive ankle stiffness was significantly correlated to balance control, ankle proprioception, and evertor peak torque. Individuals with FAI demonstrated a large variation in the deficit categories ranging from multiple deficits to no noticeable deficits.. Mechanical alterations in the ankle joint may influence several aspects of the ankle's functional ability. Alterations in the afferent processes, represented in this study by ankle proprioception, may effect the evertors' strength or vice versa. More importantly, individuals with FAI might exhibit high variability in ankle deficits.

Topics: Adult; Ankle Injuries; Ankle Joint; Case-Control Studies; Female; Humans; Joint Instability; Male; Muscle Weakness; Proprioception; Risk Factors; Sprains and Strains; Torque

Previous studies have demonstrated abnormal joint torque coupling and associated muscle coactivations of the upper extremity in individuals with unilateral stroke. We investigated the effect of upper limb configuration on the expression of the well-documented patterns of shoulder abduction/elbow flexion and shoulder adduction/elbow extension. Maximal isometric shoulder and elbow torques were measured in stroke subjects in four different arm configurations. Additionally, an isometric combined torque task was completed where subjects were required to maintain various levels of shoulder abduction/adduction torque while attempting to maximize elbow flexion or extension torque. The dominant abduction/elbow flexion pattern was insensitive to changes in limb configuration while the elbow extension component of the adduction/extension pattern changed to elbow flexion at smaller shoulder abduction angles. This effect was not present in control subjects without stroke. The reversal of the torque-coupling pattern could not be explained by mechanical factors such as muscle length changes or muscle strength imbalances across the elbow joint. Potential neural mechanisms underlying the sensitivity of the adduction/elbow extension pattern to different somatosensory input resultant from changes in limb configuration are discussed along with the implications for future research.

Topics: Adult; Aged; Arm; Brain; Efferent Pathways; Elbow Joint; Electromyography; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Neuronal Plasticity; Paresis; Posture; Proprioception; Range of Motion, Articular; Recovery of Function; Stroke; Torque

The effect of age on mechanomyography (MMG) has not been examined for electrically evoked contractions. Similar to torque, we expected that postactivation potentiation of the MMG would differ between young and old subjects. Additionally, under voluntary conditions, we compared normalized MMG and electromyographic (EMG) signals in relation to torque, and expected that MMG, unlike EMG, would be affected by age. In 10 young and 10 old men, electrical stimulation was delivered before and after a 10-s maximal voluntary contraction (MVC) to assess potentiation of contractile (twitch torque; Pt), electrical (M-wave amplitude), and mechanical (MMG amplitude) properties of the dorsiflexors. Subsequently, subjects performed voluntary contractions at 20%, 40%, 60%, 80%, and 100% MVC for calculation of normalized MMG-torque and EMG-torque relationships. Following the MVC, Pt and evoked MMG were larger than at rest in both groups, but M-wave amplitude was unchanged. Twitch potentiation was greater in young than old, whereas evoked MMG was unaffected by age. Under voluntary conditions, values for MMG and EMG were similar between groups, except for greater MMG at MVC in young men. The shape of MMG and EMG relationships to torque was similar only in young men. Using the aging model, our results indicate that potentiation of the mechanical components (MMG) differ from those of twitch torque. Furthermore, the comparison of normalized voluntary MMG with age provides additional support for the concept of age-related motor unit remodeling.

Topics: Action Potentials; Adult; Aged; Aged, 80 and over; Aging; Biomechanical Phenomena; Electric Stimulation; Electromyography; Humans; Male; Muscle Contraction; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Neuromuscular Junction; Predictive Value of Tests; Reaction Time; Stress, Mechanical; Torque; Volition

To examine the reliability of clinical techniques for testing hip abductor and adductor muscle performance.. Repeated measures.. Academic laboratory.. A sample of 21 healthy subjects (12 men, 9 women) between 22 and 31 years of age.. Not applicable.. Reliability of repeated measures was estimated by calculating intraclass correlation coefficients. Torque production capability was calculated by multiplying force output obtained with a hand-held dynamometer by the length of the resistance lever arm.. The reliability of abduction testing was greatest in the long-lever condition. Adduction test reliability was greatest in the long-lever condition with bench stabilization. The maximal hip abduction torque tested in the long-lever position was significantly greater (t(20)=9.21, P<.001) than that in the short-lever position. The maximal hip adduction torque occurred using a long lever for resistance application and a bench to stabilize the nontest leg (F(1,20)=15.64, P=.001).. Muscle performance testing of hip abductors and adductors with a hand-held dynamometer can be performed with good to excellent intratester and intertester reliability. Hip abduction testing is best performed with a long lever. Hip adduction is best performed with a long lever and a bench to stabilize the nontest extremity.

Topics: Adult; Analysis of Variance; Body Height; Body Mass Index; Body Weight; Equipment Design; Female; Hip; Humans; Male; Minnesota; Muscle Contraction; Muscle Strength Dynamometer; Muscle Weakness; Observer Variation; Physical Examination; Pronation; Sensitivity and Specificity; Single-Blind Method; Supination; Torque

Maximal strength decreases with aging whereas sustained strength is less affected. Strength decline may be worsened by hospitalization. The aim of this study was to estimate the maximal and sustained isokinetic muscle strength of lower limbs in hospitalized elderly subjects. We evaluated 43 hospitalized elderly subjects (86 +/- 5 years), 28 elderly community-dwelling control subjects (75.4 +/- 6.2 years), and 25 young subjects (28.2 +/- 3.7 years). Among hospitalized subjects, 30 underwent isokinetic evaluation at clinical stability (T0) and again 1 month later (T1). Maximal peak torque (MPT) of the plantarflexors was measured at 30 degrees and 60 degrees /s, and knee flexors and extensors at 90 degrees /s. Evolution of the MPT and the endurance coefficient (EC) on 20 repetitions of plantarflexion at 60 degrees /s were calculated. MPT of plantarflexors and knee flexors and extensors had improved at T1 compared with T0, in hospitalized subjects. MPT evolution and EC values during the sustained strength test revealed no decrease in strength over time in hospitalized subjects at T0 and at T1 compared with community-dwelling control subjects and young subjects. In hospitalized subjects, the absence of an initial phase of fast decrease in muscle strength, which is observed in young subjects during the sustained strength test, could explain this result. It could be related to the modifications of muscle-fiber composition described in elderly subjects and enhanced by hospitalization.

Topics: Adult; Aged; Aged, 80 and over; Aging; Disease Progression; Female; Hospitalization; Humans; Inpatients; Isometric Contraction; Leg; Length of Stay; Male; Muscle Fatigue; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Muscular Disorders, Atrophic; Torque

To examine the efficiency of the difference between the isokinetic eccentric to concentric strength ratios at high and low velocities (DEC) for identifying feigned maximal shoulder external rotation effort.. Previous studies have indicated that the DEC is a powerful identifier of feigned maximal effort. However comparison of maximal versus feigned maximal shoulder external rotation effort has not been undertaken. Due to the high prevalence of rotational shoulder disorders and their chronic ramifications in terms of occupational disability such a study is of specific interest.. Maximal and feigned maximal shoulder external rotation isokinetic efforts were compared.. Functional evaluation unit at an occupational rehabilitation centre.. Seventeen healthy male volunteers aged between 20 and 40 years old.. Concentric and eccentric isokinetic tests at 30 degrees /s and 120 degrees /s in maximal and feigned maximal experimental conditions. DEC was calculated by subtracting the 30 degrees /s eccentric/concentric peak torque ratios from the 120 degrees /s ones for both experimental conditions.. A case-by-case analysis revealed that the DEC scores derived from the feigned effort were significantly greater than their maximal counterparts in all cases, leading to a cut-off value (0.81) which could distinguish between maximal and feigned performances.. The findings indicate that the DEC is highly effective in identifying feigned shoulder external rotation effort in normal subjects.

Topics: Adult; Deception; Humans; Male; Muscle Contraction; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Physical Examination; Rotation; Shoulder Joint; Torque

The ability to extend the elbow following stroke depends on the magnitude and direction of torques acting at the shoulder. The mechanisms underlying this link remain unclear. The purpose of this study was to evaluate whether the effects of shoulder loading on elbow function were related to weakness or its distribution in the paretic limb. Ten subjects with longstanding hemiparesis performed movements with the arm either passively supported against gravity by an air bearing, or by activation of shoulder muscles. Isometric maximum voluntary torques at the elbow and shoulder were measured using a load cell. The speed and range of elbow extension movements were negatively impacted by actively supporting the paretic limb against gravity. However, the effects of gravity loading were not related to proximal weakness or abnormalities in the elbow flexor-extensor strength balance. The findings support the existence of abnormal descending motor commands that constrain the ability of stroke survivors to generate elbow extension torque in combination with abduction torque at the shoulder.

Topics: Adult; Aged, 80 and over; Analysis of Variance; Biomechanical Phenomena; Elbow; Female; Gravitation; Humans; Male; Middle Aged; Muscle Weakness; Psychomotor Performance; Range of Motion, Articular; Shoulder; Stroke; Torque

Patients with nemaline myopathy, a muscle disorder primarily affecting the thin filaments, suffer from weakness which is poorly understood. As disturbed excitation-contraction coupling has been suggested as a possible mechanism, the present study was designed to investigate whether the contractile properties of the knee-extensor muscles in patients from a single family with nemaline myopathy were different from able-bodied individuals. To assess central neural as well as more peripheral intrinsic aspects of muscle activation, isometric voluntary and electrically elicited quadriceps contractions were evoked at different knee angles. Interestingly, across the range of 30-70 degrees of knee flexion, the capacity to achieve maximal voluntary activation of the muscles, assessed by a super-imposed stimulation technique, was significantly higher in patients compared with controls. Furthermore, the torque-frequency relation differed between groups, with the muscles of patients producing higher torques at low (twitch and 10 Hz) stimulation frequencies relative to maximal (150 Hz) stimulation than controls at both 30 degrees and 60 degrees of knee flexion. These results suggest that no impairment was present at relatively low activation frequencies. It may, however, be indicative for a reduced cross-bridge attachment as part of the excitation-contraction coupling specifically at high activation frequencies. In conclusion, the quadriceps weakness observed in this specific patient group cannot be explained by an impaired capacity to maximally activate these muscles. However, the data of relatively high torques produced at submaximal activation frequencies are compatible with the hypothesis that patients with nemaline myopathy may have an impaired acto-myosin interaction specifically at high levels of activation.

Topics: Adult; Aged; Analysis of Variance; Case-Control Studies; Electric Stimulation; Female; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Myopathies, Nemaline; Phenotype; Torque

The aim of this study was to evaluate the effects of neuromuscular electrical stimulation (NMES) training and subsequent detraining on neuromuscular fatigue mechanisms. Ten young healthy men completed one NMES fatigue protocol before and after a NMES training program of 4 weeks and again after 4 weeks of detraining. Muscle fatigue (maximal voluntary torque loss), central fatigue (activation failure), and peripheral fatigue (transmission failure and contractile failure) of the plantar flexor muscles were assessed by using a series of electrically evoked and voluntary contractions with concomitant electromyographic and torque recordings. At baseline, maximal voluntary torque decreased significantly with fatigue (P<0.001), due to both activation and transmission failure. After detraining, maximal voluntary torque loss was significantly reduced (P<0.05). In the same way, the relative decrease in muscle activation after training and detraining was significantly lower compared to baseline values (P<0.05). Short-term NMES training-detraining of the plantar flexor muscles significantly reduced the muscle fatigue associated to one single NMES exercise session. This was mainly attributable to a reduction in activation failure, i.e., lower central fatigue, probably as a result of subject's accommodation to pain and discomfort during NMES.

Topics: Adult; Electric Stimulation Therapy; Electromyography; Exercise; Exercise Tolerance; Fatigue Syndrome, Chronic; Humans; Male; Muscle Contraction; Muscle Fatigue; Muscle Strength; Muscle Weakness; Muscle, Skeletal; Neuromuscular Junction; Physical Fitness; Torque

We investigated the control of movement in 12 patients with Parkinson's disease (PD) after they received surgically implanted high-frequency stimulating electrodes in the subthalamic nucleus (STN). The experiment studied ankle strength, movement velocity, and the associated electromyographic patterns in PD patients, six of whom had tremor at the ankle. The patients were studied off treatment, ON STN deep brain stimulation (DBS), on medication, and on medication plus STN DBS. Twelve matched control subjects were also examined. Medication alone and STN DBS alone increased patients' ankle strength, ankle velocity, agonist muscle burst amplitude, and agonist burst duration, while reducing the number of agonist bursts during movement. These findings were similar for PD patients with and without tremor. The combination of medication plus STN DBS normalized maximal strength at the ankle joint, but ankle movement velocity and electromyographic patterns were not normalized. The findings are the first to demonstrate that STN DBS and medication increase strength and movement velocity at the ankle joint.

Topics: Ankle Joint; Antiparkinson Agents; Biomechanical Phenomena; Carbidopa; Combined Modality Therapy; Deep Brain Stimulation; Electrodes, Implanted; Electromyography; Humans; Hypokinesia; Isometric Contraction; Levodopa; Muscle Weakness; Muscle, Skeletal; Parkinson Disease; Reference Values; Signal Processing, Computer-Assisted; Statistics as Topic; Torque; Treatment Outcome; Tremor

Cortical activation is reduced when patients with focal dystonia perform movements that do not induce dystonic posturing. This finding suggests that the cortical drive to muscles may in some circumstances actually be reduced not increased, as suggested by basal ganglia models of dystonia as a hyperkinetic disorder. The purpose of this study was to examine flexor and extensor strength at the wrist (a clinically affected joint) and elbow (a nonclinically affected joint) in 18 patients with primary focal hand dystonia compared to matched control subjects. We measured peak torque from maximum voluntary contractions, and agonist and antagonist muscle activation by means of surface electromyograms. Patients were significantly weaker than controls at both the elbow and wrist joints and in both flexors and extensors compared to controls. Peak elbow flexion torque was, on average, 14.4% lower in the dystonic compared to the control group, elbow extensor peak torque was 28.6% lower, wrist flexor peak torque was 17.4% lower, and wrist extensor peak torque was 20.7% lower. Strength did not differ as a function of clinical severity. Reductions in peak torque were accompanied by reduced agonist activation, although this finding only reached statistical significance at the elbow. The amount of co-contraction of antagonistic muscles was not significantly different between the two groups. These results are discussed in the context of dystonia as a disorder resulting from dysfunction of basal ganglia output.

Topics: Adult; Cerebral Cortex; Dystonic Disorders; Electromyography; Female; Hand; Humans; Isometric Contraction; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Reference Values; Torque; Wrist

A decrease of deep knee flexion torque after anterior cruciate ligament (ACL) reconstruction, using a semitendinosus (and gracilis) tendon, has been reported. However, the cause of this weakness remains controversial. Architectural and functional differences in the knee flexor muscles influence this weakness. the fiber length of the semitendinosus, gracilis, semimembranosus, and biceps femoris were directly measured in six human cadavers. The flexion torque and EMG of the hamstrings were measured in both limbs of 16 patients (23+/-5 years) after ACL reconstruction (12-43 months post-operation), using ipsilateral semitendinosus tendon. Magnetic resonance imagings were taken, over both the thighs of those patients, to measure muscle volume and to confirm a state of semitendinosus tendon regeneration. The position of the musculotendinous junction of the semitendinosus was also analyzed. The fiber length of the semitendinosus and gracilis were three to four times longer than that of the semimembranosus and biceps femoris. The difference of flexion torque between the normal and ACL reconstructed limbs significantly increased as the knee flexion angle increased. The EMG value for the semimembranosus and biceps femoris of both limbs as well as the semitendinosus of the ACL reconstructed limbs, significantly reduced as the knee flexion angle was increased. The volume of the semitendinosus in the reconstructed limb was significantly smaller than in normal limbs. The regeneration of the semitendinosus tendon was confirmed in all subjects, and the musculotendinous junction position of the reconstructed limb in almost all subjects was found in further image from the knee joint space than that for the normal limb. The decrease of deep knee flexion torque, after ACL reconstruction, could be due to the atrophy and shortening of the semitendinosus after its tendon has been harvested, as well as the lack of compensation from the semimembranosus and biceps femoris, due to the architectural differences between the semitendinosus and the semimembranosus and biceps femoris.

Topics: Achilles Tendon; Adult; Anterior Cruciate Ligament; Cadaver; Electromyography; Female; Follow-Up Studies; Humans; Isometric Contraction; Knee Joint; Magnetic Resonance Imaging; Male; Middle Aged; Muscle Fibers, Skeletal; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Plastic Surgery Procedures; Range of Motion, Articular; Regeneration; Tendons; Thigh; Torque

Separation of tendon ends after Achilles tendon repair may affect the tendon repair process and lead to postoperative end-range plantarflexion weakness.. Patients will have disproportionate end-range plantarflexion weakness after Achilles tendon repair.. Descriptive laboratory study.. Four-strand core suture repairs of Achilles tendon were performed on 1 female and 19 male patients. Postoperatively, patients were nonweightbearing with the ankle immobilized for 4 weeks. Plantarflexion torque, dorsiflexion range of motion, passive joint stiffness, toe walking, and standing single-legged heel rise (on an incline, decline, and level surface) were assessed after surgery (mean, 1.8 years postoperative; range, 6 months-9 years). Maximum isometric plantarflexion torque was measured at 20 degrees and 10 degrees of dorsiflexion, neutral, and 10 degrees and 20 degrees of plantar flexion. Percentage strength deficit (relative to noninvolved leg) was computed at each angle. Passive dorsiflexion range of motion was measured goniometrically. Passive joint stiffness was computed from increase in passive torque between 10 degrees and 20 degrees of dorsiflexion, before isometric contractions.. Significant plantarflexion weakness was evident on the involved side at 20 degrees and 10 degrees of plantar flexion (34% and 20% deficits, respectively; P <.001), with no torque deficits evident at other angles (6% at neutral, 3% at 10 degrees of dorsiflexion, 0% at 20 degrees of dorsiflexion). Dorsiflexion range of motion was not different between involved and noninvolved sides (P = .7). Passive joint stiffness was 34% lower on the involved side (P <.01). All patients could perform an incline heel rise; 14 patients could not perform a decline heel rise (P <.01).. Disproportionate weakness in end-range plantar flexion, decreased passive stiffness in dorsiflexion, and inability to perform a decline heel rise are evident after Achilles tendon repair. Possible causes include anatomical lengthening, increased tendon compliance, and insufficient rehabilitation after Achilles tendon repair.. Impairments will have functional implications for activities (eg, descending stairs and landing from a jump). Weakness in end-range plantar flexion may be an unrecognized problem after Achilles tendon repair.

Topics: Achilles Tendon; Adult; Ankle Injuries; Ankle Joint; Female; Heel; Humans; Leg; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Range of Motion, Articular; Recovery of Function; Rupture; Torque

This pilot study examined the effects of neuromuscular electrical stimulation (NMES) therapy on upper limb impairment in children with cerebral palsy, specifically addressing spasticity, heightened passive resistance to wrist rotation, coactivation, and weakness.. Eight subjects, aged five to 15 years, with spastic hemiparesis subsequent to brain injury, participated in three months of NMES therapy, targeting the wrist flexor and extensor muscles. Maximum voluntary wrist extension range of motion against gravity, spasticity, passive torque, maximum voluntary isometric torque, and coactivation were recorded prior to, during, and at the conclusion of the therapy.. Seven of the eight subjects demonstrated a significant (>15 degrees) improvement in wrist extension range of motion against gravity following the NMES treatment, with an average gain of 38 degrees. Differences in spasticity (0.01 +/- 0.14 N-m, p = 0.80) and passive torque (0.03 +/- 0.11 N-m, p = 0.52) were not significant for these subjects. Isometric wrist extension torque, however, did increase significantly (p < 0.01), accompanied by a reduction in flexor coactivation (p < 0.01).. Evidence suggests that the NMES treatment protocol affected wrist extension by improving the strength of the wrist extensor muscles, possibly through decreased flexor coactivation. Further studies are required, however, to determine whether electrical stimulation itself or other facets of the therapy paradigm played the key role in improvement.

Topics: Adolescent; Brain Injuries; Cerebral Palsy; Child; Child, Preschool; Electric Stimulation Therapy; Electromyography; Female; Hand Strength; Humans; Male; Muscle Spasticity; Muscle Weakness; Paraparesis, Spastic; Pilot Projects; Range of Motion, Articular; Torque; Treatment Outcome; Upper Extremity; Wrist Joint

The neurophysiological mechanisms for persisting impairment of motor function after Guillain-Barre syndrome (GBS) were assessed in 37 unselected patients 1-13 years after diagnosis. For evaluation of reinnervation and axonal loss, macroelectromyography (macro-EMG) including measurement of fiber density (FD) was performed. Data from neuropathy symptom score, neuropathy disability score, nerve conduction studies, and quantitative sensory examination were ranked and summed to a neuropathy rank sum score (NRSS). The isokinetic muscle strength at the ankle was measured. Signs of axonal loss with increase of either macro motor unit potential (macro-MUP) amplitude or FD occurred in 76% of patients. The macro-MUP amplitude correlated with muscle strength and with NRSS. Patients with evidence of residual neuropathy had increased macro-MUP amplitude and FD as well as decreased muscle strength compared to patients without evidence of residual neuropathy. We conclude that axonal loss takes place in a substantial number of GBS patients and is associated with permanent muscle weakness caused by insufficient reinnervation. Possible patterns of pathology are discussed in relation to the macro-EMG findings.

Topics: Adult; Aged; Ankle Joint; Axons; Cross-Sectional Studies; Electromyography; Female; Follow-Up Studies; Guillain-Barre Syndrome; Humans; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Nerve Regeneration; Neural Conduction; Sensory Thresholds; Torque; Vibration

While the pathogenesis of Botulinum toxin type A (BTX-A)-induced muscle weakness has been systematically researched, little is known about the effects of motor fibre paralysis on the mechanical properties of skeletal muscle. Here, the long-term effect of BTX-A injection on the force-length and force-frequency properties of rabbit knee extensors is investigated. BTX-A-induced muscle weakness was greater at short compared to long muscle lengths and at low compared to high stimulation frequencies four weeks following intervention. Therefore, we conclude that the paralysing effects of BTX-A are not uniform, and must be considered in biomechanical models of musculoskeletal rehabilitation in which BTX-A is used therapeutically, as for example in patients with cerebral palsy. Although the present results could be explained through a variety of mechanisms, this study does not allow for drawing firm conclusions about the length and frequency-dependent effects of BTX-A.

Topics: Animals; Biomechanical Phenomena; Botulinum Toxins, Type A; Joints; Muscle Weakness; Muscle, Skeletal; Paralysis; Rabbits; Time Factors; Torque

We established botulinum type-A toxin (BTX-A) injections as a powerful tool to cause knee extensor weakness in New Zealand White (NZW) rabbits. The purpose of this study was to determine if BTX-A induced quadriceps weakness causes muscle dysfunction beyond that caused by anterior cruciate ligament (ACL) transection in the knee of NZW rabbits. Twenty animals were randomly divided into four study groups (n=5 each); uninjected controls, BTX-A injection alone, ACL transection alone, BTX-A injection and ACL transection combined. Isometric knee extensor torque, quadriceps muscle mass, and vertical and anterior-posterior ground reaction forces were measured four weeks post single (BTX-A and ACL), unilateral intervention. Muscle weakness, muscle atrophy and decrease in ground reaction forces were all significantly greater for the experimental compared to the untreated contralateral legs. BTX-A injection produced a greater deficit in quadriceps mass and knee extensor torque than ACL transection alone, but produced smaller deficits in the ground reaction forces. ACL transection superimposed on BTX-A injection did not change either knee extensor torque production or muscle mass. Together these results suggest that BTX-A injection causes great force and muscle mass deficits, and affects functional gait in a significant manner, but it has no measurable functional effect when superimposed on ACL transection, at least not in the acute protocol tested here. Hopefully, BTX-A injection for acutely enhancing the degree of muscle weakness in otherwise untreated animals, or in experimental models of osteoarthritis, will help in investigating the role of muscle weakness in joint degeneration.

Topics: Animals; Anterior Cruciate Ligament Injuries; Botulinum Toxins; Gait; Joint Instability; Knee Injuries; Muscle Weakness; Muscular Atrophy; Rabbits; Torque

Osteoarthritic patients show only a weak association between radiographic signs of joint disease and joint pain and disability. Conversely, muscle weakness is one of the earliest and most common symptoms of patients with osteoarthritis (OA). However, while many experimental models of osteoarthritis include a component of muscular weakness, no model has isolated this factor satisfactorily. Therefore, the purpose of this study was to develop and validate an experimental animal model of muscle weakness for future use in the study of OA. Botulinum Type-A toxin (BTX-A) was uni-laterally injected into the quadriceps musculature of New Zealand white rabbits (3.5 units/kg). Isometric knee extensor torque at a range of knee angles and stimulation frequencies, and quadriceps muscle mass, were quantified for control animals, and at one- and six-months post-repeated injections, in both, the experimental and the contralateral hindlimb. Ground reaction forces were measured in all animals while hopping across two force platforms. Isometric knee extension torque and quadriceps muscle mass was systematically decreased in the experimental hindlimb. Vertical ground reaction forces in the push off phase of hopping were also decreased in the experimental compared to control hindlimbs. We conclude that BTX-A injection into the rabbit musculature creates functional and absolute muscle weakness in a reproducible manner. Therefore, this model may be used to systematically study the possible effects of muscle weakness on joint degeneration, either as an isolated intervention, or in combination with other interventions (anterior cruciate ligament transection, meniscectomy) known to create knee joint degeneration.

Topics: Animals; Botulinum Toxins; Disease Models, Animal; Knee Joint; Muscle Weakness; Muscle, Skeletal; Osteoarthritis; Rabbits; Torque

Anterior cruciate ligament (ACL) rupture causes instability to the knee joint which leads each patient to a different degree of disability. The purpose of this study was to examine the strength of the quadriceps and the hamstrings in ACL-deficient amateur soccer players at different levels of functional status. Thirty male amateur soccer players were separated into three groups according to their Lysholm score; the high-L1 (Lysholm > or =84), the intermediate-L2 (84> Lysholm > or =72) and the low-L3 (Lysholm <72) knee function groups. The control group consisted of 12 amateur soccer players. The strength of the quadriceps and hamstrings was assessed isokinetically at 60 degrees/s. The quadriceps demonstrated significant deficits of the injured knee compared to the intact knee in all groups, whilst the hamstrings showed significant weakness only in the low function group. Respective percentage deficits in groups L1, L2 and L3 were 13.7%, 16.0% and 18.6% for the quadriceps and 2.4%, 5.6% and 19.2% for the hamstrings. All groups had significant quadriceps weakness which did not differ between the groups. In contrast, the strength deficit of the hamstrings was an indicator of poor knee function, since they were significantly weak only in group L3, which represented patients who clearly failed to compensate for instability symptoms. In groups L1 and L2 the side-to-side differences were within the area of asymmetry measured in the control group. Clinical importance of the results is discussed.

Topics: Adult; Anterior Cruciate Ligament Injuries; Case-Control Studies; Humans; Joint Instability; Knee Joint; Male; Muscle Weakness; Muscle, Skeletal; Soccer; Torque

To determine if quadriceps activation failure (QAF) moderates the relationship between quadriceps strength and physical function in individuals with knee osteoarthritis (OA).. Quadriceps strength and QAF were measured in 105 subjects (80 females) with radiographically confirmed knee OA using a burst-superimposition maximum voluntary isometric quadriceps torque test procedure. Subjects performed the Get Up and Go test as a physical performance measure of function and completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) as a self-report measure of function. A principal component analysis was performed to combine the Get Up and Go score and the WOMAC subscores into a single function score. Hierarchical regression analysis was performed to examine the ability of 3 models to predict physical function (strength = function; strength + QAF = function; strength + QAF + [strength x QAF] = function). Partial F tests were used to compare differences in R(2) values between each model.. Each model independently predicted the principal component score for function. Adding the strength x QAF interaction term with strength to the model resulted in the highest prediction of function. The strength x QAF interaction indicated that subjects with lower levels of quadriceps strength and higher levels of QAF had lower levels of function than those with comparable levels of weakness but low levels of QAF.. The magnitude of QAF serves to moderate the relationship between quadriceps strength and physical function. Physical function may be more severely affected by weakness of the quadriceps muscles in individuals with knee OA who have higher degrees of QAF than those who may have quadriceps weakness, but do not have QAF.

Topics: Exercise Test; Female; Health Status; Humans; Isometric Contraction; Male; Models, Theoretical; Muscle Weakness; Muscle, Skeletal; Osteoarthritis, Knee; Self Care; Severity of Illness Index; Surveys and Questionnaires; Torque

To compare lower-leg strength of young girls with polyarticular juvenile idiopathic arthritis (JIA) with that of healthy, age-matched controls.. Isometric and isokinetic strength tests of the plantar- and dorsiflexors. All strength measures were made at an ankle angle of 90 degrees. Isokinetic plantar- and dorsiflexor measures were made at 15 degrees/s during shortening (concentric) and lengthening (eccentric) actions.. Strength testing laboratory.. Ten prepubertal girls diagnosed with JIA and 10 healthy girls.. Not applicable.. Isometric and isokinetic plantar- and dorsiflexor strength.. Isometric plantar- and dorsiflexion torques were significantly lower (48% and 38% respectively; P<.05) for the children with JIA than for the controls. The JIA group also produced lower shortening plantarflexion torques (52%, P<.05). Lengthening plantarflexor torques did not differ significantly between the 2 groups (P<.05). Controls were stronger than the JIA group for both shortening and lengthening maximal dorsiflexor actions (P<.05). All children were 4 to 5 times stronger in plantarflexion than in dorsiflexion.. Girls with JIA had significantly less plantar- and dorsiflexor strength than age-matched, healthy peers. The reduced strength of children with JIA is likely to affect function in daily activities and probably contributes to reduced levels of physical activity.

Topics: Activities of Daily Living; Age Factors; Ankle; Arthritis, Juvenile; Body Height; Body Mass Index; Case-Control Studies; Child; Disease Progression; Female; Foot; Humans; Isometric Contraction; Isotonic Contraction; Muscle Weakness; Physical Therapy Modalities; Range of Motion, Articular; Sex Characteristics; Torque

To determine what changes in maximal isometric strength can be detected in a symptomatic quadriceps muscle in patients with postpoliomyelitis syndrome (PPS) and to investigate the association between the variability in maximal strength and maximal voluntary activation (MVA).. Repeated-measures over a 3-week interval.. University hospital.. Convenience sample of 65 patients with PPS.. Dynamometer testing.. Maximal voluntary contraction (MVC) torque of the quadriceps was measured with a Kin-Com dynamometer and MVA was determined by twitch interpolation.. The mean difference between the 2 consecutive measurements was -0.7+/-12.8 Nm (95% confidence interval [CI], -3.9 to 2.5). The test-retest reliability was excellent for MVC torque (intraclass correlation coefficient [ICC]=.96; 95% CI,.93-.98) and moderate for MVA (ICC=.73; 95% CI,.56-.85). The smallest detectable change in MVC torque was 25% for an individual. The variability in MVA explained 18% of the variability in maximal strength.. Variability in maximal quadriceps strength, measured with a fixed dynamometer, was large and partly related to variability in MVA. This implies that even with optimally standardized strength testing, a follow-up of many years is required to objectify progression of quadriceps weakness in an individual patient with PPS. To demonstrate changes in strength in groups of patients in follow-up or intervention studies, feasible sample sizes are required.

Topics: Adult; Aged; Analysis of Variance; Bias; Disease Progression; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle Weakness; Physical Therapy Modalities; Postpoliomyelitis Syndrome; Sample Size; Sensitivity and Specificity; Severity of Illness Index; Time Factors; Torque

To determine and compare lower-limb force production during a single-leg horizontal press in involved and uninvolved limbs in people with unilateral total knee arthroplasty (TKA) and the limb of age- and gender-matched subjects.. Quasi-experimental, posttest only control group design.. Subjects living in the community and were tested at a university facility.. Nine people with unilateral TKA and 9 subjects without TKA volunteered. The mean postsurgery time for the TKA group was 15.89+/-6.62 months.. Not applicable.. Force production in kilograms during a single-leg press.. Lower-limb force production differed significantly between involved and uninvolved limbs (P=.007) for the unilateral TKA group. Lower-limb force production of the involved limb in persons with unilateral TKA was significantly lower than the limb of the age- and gender-matched controls (P=.0001).. Lower-limb force production on the involved side was significantly lower than the uninvolved side. When compared with an age-matched control group, subjects with unilateral TKA produced less force during a single-leg horizontal press.

Topics: Activities of Daily Living; Aged; Analysis of Variance; Arthroplasty, Replacement, Knee; Biomechanical Phenomena; Body Height; Body Mass Index; Body Weight; Case-Control Studies; Elasticity; Exercise Therapy; Female; Humans; Isometric Contraction; Knee Prosthesis; Lower Extremity; Male; Middle Aged; Muscle Weakness; Needs Assessment; Range of Motion, Articular; Torque; Weight-Bearing

To evaluate neck flexion, extension, and, especially, rotation strength in women with chronic neck pain compared with healthy controls and to evaluate the repeatability of peak isometric neck strength measurements in patients with neck pain.. Cross-sectional.. Rehabilitation center and physical and rehabilitation medicine department at a Finnish hospital.. Twenty-one women with chronic neck pain and healthy controls matched for sex, age, anthropometric measures, and occupation.. Not applicable.. Peak isometric strength of the cervical muscles was tested in rotation, flexion, and extension.. Significantly lower flexion (29%), extension (29%), and rotation forces (23%) were produced by the chronic neck pain group compared with controls. When the repeated test results were compared pairwise against their mean, considerable variation was observed in the measures on the individual level. Intratester repeatability of the neck muscle strength measurements was good in all the 4 directions tested in the chronic neck pain group (intraclass correlation coefficient range,.74-.94). The coefficient of repeatability was 15N, both in flexion and extension, and 1.8 Nm in rotation. On the group level, improvement up to 10% due to repeated testing was observed.. The group with neck pain had lower neck muscle strength in all the directions tested than the control group. This factor should be considered when planning rehabilitation programs. Strength tests may be useful in monitoring training progress in clinical settings, but training programs should be planned so that the improvement in results is well above biologic variation, measurement error, and learning effect because of repeated testing.

Topics: Adult; Analysis of Variance; Body Height; Body Mass Index; Body Weight; Case-Control Studies; Chronic Disease; Cross-Sectional Studies; Female; Finland; Hand Strength; Head Movements; Humans; Isometric Contraction; Middle Aged; Muscle Weakness; Neck Muscles; Neck Pain; Observer Variation; Physical Therapy Modalities; Range of Motion, Articular; Rotation; Torque

To define the relative hip extensor muscle strengths values identified by the 4 grades obtained with a supine manual muscle test (MMT) and to compare these values with those indicated by the traditional prone test.. Comparison of 4 manual supine strength grades with isometric hip extension joint torque; kappa statistic-determined interrater reliability, and analyses of variance identified between grade differences in torque.. Pathokinesiology laboratory.. Adult volunteers recruited from local community and outpatient clinics. Reliability testing: 16 adults with postpolio (31 limbs). Validity testing (2 groups): 18 subjects without pathology (18 limbs), and 26 people with clinical signs of hip extensor weakness (51 limbs).. Not applicable.. Supine hip extensor manual muscle grade and isometric hip extension torque.. Reliability testing showed excellent agreement (82%). Subjects with pathology had significant differences in mean torque (P<.01) for the assigned grade 5 (176 Nm), grade 4 (103 Nm), grade 3 (67 Nm), and grade 2 (19 Nm). Healthy adults showed significant differences between grade 5 (212 Nm) and grade 4 (120 Nm) in mean torque (P<.05).. The supine MMT is a reliable and valid method with which to assess hip extension strength.

Topics: Activities of Daily Living; Aged; Analysis of Variance; Case-Control Studies; Female; Guillain-Barre Syndrome; Hip Joint; Humans; Isometric Contraction; Los Angeles; Male; Middle Aged; Muscle Weakness; Observer Variation; Osteoarthritis, Hip; Physical Examination; Physical Therapy Modalities; Polyradiculopathy; Postpoliomyelitis Syndrome; Prone Position; Range of Motion, Articular; Severity of Illness Index; Supine Position; Torque

Several studies have reported lower neck muscle strength in patients with chronic neck pain compared to healthy controls. The aim of the present study was to evaluate the association between the severity of neck pain and disability with neck strength and range of movement in women suffering from chronic neck pain. One hundred and seventy-nine female office workers with chronic neck pain were selected to the study. The outcome was assessed by the self-rating questionnaires on neck pain (visual analogue scale, Vernon's disability index, Neck pain and disability index) and by measures of the passive range of movement (ROM) and maximal isometric neck muscle strength. No statistically significant correlation was found between perceived neck pain and the disability indices and the maximal isometric neck strength and ROM measures. However, the pain values reported during the strength tests were inversely correlated with the results of strength tests (r=-0.24 to -0.46), showing that pain was associated with decreased force production. About two-thirds of the patients felt pain during test efforts. Pain may prevent full effort during strength tests and hence the production of maximal force. Thus in patients with chronic neck pain the results do not always describe true maximal strength, but rather the patients' ability to bear strain, which may be considerably influenced by their painful condition. The results of the present study suggest that rehabilitation in cases of chronic neck pain should aim at raising tolerance to mechanical strain.

Topics: Adult; Cervical Vertebrae; Chronic Disease; Disability Evaluation; Female; Finland; Head Movements; Humans; Isometric Contraction; Middle Aged; Muscle Contraction; Muscle Weakness; Neck Muscles; Neck Pain; Occupational Diseases; Pain Threshold; Range of Motion, Articular; Stress, Mechanical; Surveys and Questionnaires; Torque; Weight-Bearing

To investigate the power output generation from anterior cruciate ligament (ACL)-injured and noninjured limbs during stationary cycling.. Repeated measures.. Research laboratory.. Ten people with unilateral ACL deficiency and 10 uninjured controls matched for age and sex.. Participants performed 6 randomized bouts of stationary cycling at intensities of 2 cadences (60, 90 rpm) and 3 power outputs (75, 125, 175 W) for approximately 2 minutes for each bout during a single laboratory visit.. The effective component of force (perpendicular to the crank) was measured and used to calculate the power output contribution from each limb to the total power output.. Subjects with ACL injury generated significantly more power from uninjured limbs compared with that from injured limbs and the limbs of control subjects.. Results suggest that people with ACL injury have a reduced total output from the injured limb and rely on the uninjured limb for most of the power output. This may compromise the ability to restore lower-limb muscle strength after injury.

Topics: Analysis of Variance; Anterior Cruciate Ligament Injuries; Bicycling; Biomechanical Phenomena; Case-Control Studies; Exercise Test; Exercise Therapy; Factor Analysis, Statistical; Female; Functional Laterality; Humans; Knee Injuries; Leg; Male; Muscle Weakness; Muscular Atrophy; Range of Motion, Articular; Severity of Illness Index; Torque

Weakness is recognized as a major problem after stroke. This study examined the torque-angle curves of stroke individuals and compared them with those of neurologically normal controls to determine (i) if stroke patients were selectively weak when their muscles were placed in a shortened range and (ii) whether contracture influenced any selective weakness. This descriptive research study measured elbow flexor and extensor torque-angle curves and contracture. Twenty-two stroke subjects who had suffered a stroke 5 months to 6 years ago and 11 neurologically normal controls of similar age participated. Torque-angle curves of the elbow flexors and extensors were determined by measuring maximum isometric torque at 0, 20, 40, 60, 80, 100 and 120 degrees of elbow flexion (0 degrees being full elbow extension), where possible. Contracture of the elbow flexors and extensors was measured as the loss of passive elbow joint range of motion. Repeated measures analysis of variance revealed that the torque-angle curves of stroke subjects (with or without contracture) were significantly different from those of the control subjects for both the elbow flexors (P < 0.05) and extensors (P < 0.05). The stroke subjects appeared relatively weaker when the muscles were in their shortened range. This study confirms that selective weakness exists at short muscle lengths after stroke. The findings of this study help to explain why people after stroke have difficulty functioning when their muscles are in their shortened range. Therefore, strength training should be targeted specifically at muscles at their shortened lengths in order to promote the recovery of function after stroke.

Topics: Aged; Case-Control Studies; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Stroke; Torque

Inspiratory muscle weakness due to lung hyperinflation and muscle wasting may occur in cystic fibrosis. We therefore measured diaphragm function and bulk in 18 stable patients with cystic fibrosis and 15 matched control subjects; the abdominal and quadriceps muscles were studied for comparison. We assessed diaphragm mass, abdominal muscle thickness, twitch transdiaphragmatic and gastric pressures, quadriceps cross-section and isokinetic strength, and lean body mass. Lean body mass, quadriceps strength, and quadriceps cross-section were lower in patients with cystic fibrosis. Twitch transdiaphragmatic pressure was 23% lower and twitch gastric pressure was 22% greater in patients with cystic fibrosis than in control subjects, but diaphragm mass and abdominal muscle thickness were similar in the two groups. For any given lean body mass and quadriceps cross-section, patients with cystic fibrosis had greater diaphragm mass and abdominal muscle thickness. Diaphragm mass had greater intersubject variability in patients with cystic fibrosis than in control subjects. We conclude that diaphragm strength is decreased but abdominal muscle strength is increased in patients with cystic fibrosis. Diaphragm and abdominal muscle bulk are not affected by the general muscle wasting, which suggests that there may be a training effect of cystic fibrosis on respiratory muscles. However, the variability of diaphragm mass indicates that this beneficial response does not occur in all patients with cystic fibrosis.

Topics: Abdominal Muscles; Adult; Anthropometry; Blood Gas Analysis; Body Composition; Body Mass Index; Case-Control Studies; Cystic Fibrosis; Diaphragm; Female; Forced Expiratory Volume; Functional Residual Capacity; Humans; Leg; Linear Models; Male; Muscle Weakness; Muscle, Skeletal; Predictive Value of Tests; Torque; Wasting Syndrome

Nemaline myopathy is a congenital neuromuscular disorder, which primarily affects the thin filaments. Clinically the most important feature is muscle weakness; however, this weakness is poorly understood. The present investigation aimed to determine the torque angle relationship of the knee extensor muscles during in vivo muscle contractions in a family with a novel phenotype of nemaline myopathy. The results of this study show that quadriceps weakness occurs predominantly at higher knee flexion angles, but relatively normal strength was found at angles closer to full knee extension. When the relative torque angle relationships were considered, torque loss at smaller than optimum knee flexion angle was greater in the patients compared with the controls. In addition, the optimum angle for maximal quadriceps torque production was shifted towards smaller knee flexion angles in the patients. This suggests that a weakness specifically at higher knee flexion angles probably occurs as a result of adaptations consequently to the disease. Furthermore, it is important to assess muscle function at different joint positions to allow adequate interpretation of muscle weakness.

Topics: Adult; Analysis of Variance; Case-Control Studies; Chromosome Mapping; Chromosomes, Human, Pair 15; Female; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Myopathies, Nemaline; Torque

The aim of this study was to determine the extent of ankle muscle weakness in children with cerebral palsy (CP) and to identify potential causes. Maximal voluntary contractions of plantar (PF) and dorsiflexors (DF) were determined at optimal angles in knee flexion and extension in both legs of 14 children with hemiplegia (7 males, 7 females) and 14 with diplegia (8 males, 6 females). Their results were compared to 14 age- and weight-matched control participants (5 males, 9 females). Muscle cross-sectional areas of soleus, posterior, and anterior compartment muscles were determined from MRIs in 14 children with CP (eight diplegia, six hemiplegia) and 18 control children. Specific tension (torque/unit area) of PF and DF was determined from torque and cross-sectional area results. Muscle volumes of PF and DF were also determined in both legs of five control children and five with hemiplegia. Muscle EMG was recorded from soleus, medial gastrocnemius, and tibialis anterior during each maximal voluntary contraction. Mean amplitude was significantly reduced in PF and DF in both CP groups and significantly higher levels of coactivation of antagonists were found compared to control participants. Strength of PF and DF was significantly reduced in both CP groups, but more importantly the muscles were found to be weak based on significantly reduced specific tensions. The PF were most affected, particularly in the group with hemiplegia. It is believed that an inability to maximally activate their muscles contributed to this weakness. A combination of incomplete activation and high levels of PF coactivation are thought to have contributed to DF weakness.

Topics: Cerebral Palsy; Child; Electromyography; Female; Hemiplegia; Humans; Magnetic Resonance Imaging; Male; Muscle Weakness; Muscle, Skeletal; Torque

In a prospective study (1993-2000), we measured the isokinetic strength of the quadriceps and hamstring muscles in 31 children aged 5-17 years, on average, 3 (1.5-5) years after treatment for a displaced femoral fracture by external fixation and early mobilization. A group of age-, sex- and weight-matched children without previous injury were used as controls. The hop-index test was used to assess the patient's confidence in the injured limb and was similar in the fractured and unfractured legs as well as in the patients and controls. We measured the peak torque output at 2 angular velocities (60 degrees/s and 180 degrees/s) in the hamstring and quadriceps muscles, using Cybex testing equipment. Torque to body weight ratios were used to compare muscle strength in patients and controls. We found no differences in muscle strength between patients and controls or in the distribution of which leg was stronger, equal or weaker in the patients or controls at any test speed. External fixation and early mobilization seem to prevent residual muscle weakness, which occurs with traction or a cast for femoral fractures in children.

Topics: Adolescent; Body Weight; Case-Control Studies; Casts, Surgical; Child; Child, Preschool; Early Ambulation; External Fixators; Female; Femoral Fractures; Fracture Fixation; Fracture Healing; Functional Laterality; Humans; Male; Muscle Weakness; Prospective Studies; Recovery of Function; Sex Characteristics; Time Factors; Torque; Traction; Treatment Outcome; Weight-Bearing

The origins of impaired finger and hand function were examined in 10 stroke survivors with chronic spastic hemiparesis, with the intent of assessing whether mechanical restraint or altered neurophysiological control mechanisms are responsible for the well-known impairment of finger extension. Simultaneous extension of all four metacarpophalangeal (MCP) joints of the impaired hand was either externally imposed using a rotary actuator or attempted voluntarily by the subject. Trials were conducted both before and after administration of a local anesthetic, blocking the median and ulnar nerves at the elbow. The anesthetic was administered to reduce the activity of the muscles flexing the MCP joints, in order to distinguish mechanical from neuronal resistance to imposed MCP rotation. We found that the nerve blockade resulted in a reduction in velocity-dependent torque (P = 0.01), thereby indicating significant joint impedance due to spasticity. Blockade also produced a posture-dependent reduction in static torque in declaratively relaxed subjects (P = 0.04), suggesting some tonic flexor activity for specific hand postures. No change in either extensor isometric (P = 0.33) or isokinetic (0.53) torque was apparent, but 3 of the 10 subjects did exhibit substantial (>10 degrees ) improvement in voluntary MCP extension following the blockade. This improvement seemed largely due to a decrease in inappropriate flexor activity during the movement, rather than an increase in extensor activity. We argue that persistent and inappropriate flexor activation plays a role in limiting voluntary finger extension, and that this activation is potentially a reflection of altered supraspinal control of key spinal pathways. In all cases, this inappropriate activation was compounded by weakness, apparent in both the extensor and flexor muscles.

Topics: Biomechanical Phenomena; Efferent Pathways; Fingers; Hemiplegia; Humans; Metacarpophalangeal Joint; Movement Disorders; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Reflex, Stretch; Stroke; Torque

To determine the distribution of weakness across elbow range of motion (ROM) in subjects with hemiparesis.. A detailed analysis of elbow torque and associated electromyographic signals of 5 prime elbow muscles generated during maximum isometric voluntary flexion (MIVF) and extension (MIVE) at 8 different elbow positions.. Rehabilitation center research laboratory.. Convenience samples of 5 controls and 10 subjects with hemiparesis with sufficient passive (>90 degrees ) and active (>60 degrees ) ROM on their paretic side.. Not applicable.. Measured and normalized MIVF and MIVE torques and normalized moving average electromyographic signals of each muscle at each testing position.. Measured MIVF and MIVE torques generated by the hemiparetic group were marginally and significantly smaller than those of the control group (2-factor repeated-measures analysis of variance [ANOVA]: P=.053 for MIVF, P=.011 for MIVE). Distribution of weakness was nonuniform across elbow positions, as shown by normalized torque-position curves. Normalized MIVE torque of the hemiparetic group was significantly and marginally smaller than that of the control group at 15 degrees and 30 degrees (Student t test: P<.0001, P=.054), respectively. Although statistically not significant, the normalized MIVF torque of the hemiparetic group was slightly larger than that of the control group but became smaller than the control group's as the elbow flexed beyond 90 degrees. Our electromyographic recordings supported the normalized MIVF torque findings, showing a significant increase in brachioradialis activation in the control group at flexed positions during MIVF (1-factor repeated-measure ANOVA, P=.003), but not in the hemiparetic group (P=.392).. Our findings suggest that measuring the strength in multiple joint positions is useful for characterizing the basic changes in muscle activation strategies and properties and provides a relevant measure of elbow weakness from a clinical and functional perspective. Various mechanisms of action are discussed to better understand the relation between joint position and weakness.

Topics: Adult; Analysis of Variance; Elbow Joint; Electromyography; Female; Hemiplegia; Humans; Isometric Contraction; Male; Middle Aged; Muscle Weakness; Range of Motion, Articular; Torque

Muscle weakness frequently accompanies conditions with musculoskeletal pain. It is not clear if this attenuation of force is due to peripheral or central processes. The effect of experimental muscle pain on maximal voluntary contraction torque and peripheral contractile properties was therefore assessed. Experimental muscle pain reduced the torque produced by isometric knee extension, but the contractile properties assessed by twitch interpolation were not affected. This indicates that force inhibition by muscle pain is centrally mediated. This has clinical implications for rehabilitation and training of patients with musculoskeletal pain.

Topics: Adult; Afferent Pathways; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Musculoskeletal Diseases; Neural Inhibition; Neurons, Afferent; Nociceptors; Pain; Pain Measurement; Reaction Time; Reflex; Spinal Cord; Torque

To obtain an objective measure of muscle force in periodic paralysis, we studied ankle dorsiflexion torque during induced paralytic attacks in hyperkalemic and hypokalemic patients. SUBJECTS, PATIENTS, AND METHODS: Dorsiflexor torque after peroneal nerve stimulation was recorded during provocative tests on 5 patients with hypokalemic or hyperkalemic disorders and on 2 control subjects (1995-2001). Manual strength assessment was simultaneously performed in a blinded fashion. Standardized provocation procedures were used.. The loss of torque in hyperkalemic patients roughly paralleled the loss of clinically detectable strength, whereas in the hypokalemic patients, pronounced torque loss occurred well before observed clinical effects. No dramatic changes occurred in the control subjects. Torque amplitude decreased more than 70% in all patients during the provocation tests; such decreases were associated with alterations induced in serum potassium concentrations.. Stimulated torque measurement offers several advantages in characterizing muscle dysfunction in periodic paralysis: (1) it is independent of patient effort; (2) it can show a definitely abnormal response early during provocative maneuvers; and (3) characteristics of muscle contraction can be measured that are unobservable during voluntary contraction. Stimulated torque measurements can characterize phenotypic muscle function in neuromuscular diseases.

Topics: Adolescent; Adult; Case-Control Studies; Disease Progression; Electric Stimulation; Glucose; Humans; Hypokalemic Periodic Paralysis; Insulin; Isometric Contraction; Muscle Weakness; Paralysis, Hyperkalemic Periodic; Peroneal Nerve; Phenotype; Potassium Chloride; Range of Motion, Articular; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Single-Blind Method; Time Factors; Torque

Although the response to intense eccentric muscle contractions is well described in normal subjects, concern exists about possible untoward effects in persons with myopathic diseases. We investigated 14 subjects with slowly progressive muscular dystrophies including myotonic muscular dystrophy (n = 9), facioscapulohumeral dystrophy (n = 2), limb-girdle syndrome (n = 2), and Becker muscular dystrophy (n = 1). Control subjects consisted of 18 able-bodied persons. Subjects performed two sets of eight maximal-effort eccentric repetitions of the elbow flexors, with measurement of maximal concentric strength, serum creatine kinase, resting and flexed arm angle, arm circumference, and soreness at days 0, 3, and 7. Although the myopathic group had less initial strength, both groups demonstrated a similar response to the protocol over 7 days. Both groups had a significant rise in serum creatine kinase, which was still elevated at 7 days (P < 0.05). The control group demonstrated a slightly greater injury response in terms of soreness, resting and flexed arm angles, and arm swelling. Both groups of subjects appeared to respond similarly to an acute bout of eccentric contractions. However, the potential long-term effects of this type of exercise in persons with myopathic diseases remains unknown.

Topics: Adult; Creatine Kinase; Elbow Joint; Exercise Therapy; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Muscular Dystrophies; Muscular Dystrophy, Duchenne; Torque

At least 280 000 hip fractures occur annually in the U.S. at an estimated cost of $9 billion. While over 90 percent of these are caused by falls, only about 2 percent of all falls result in hip fracture. Evidence suggests that the most important determinants of hip fracture risk during a fall are the body's impact velocity and configuration. Accordingly, protective responses for reducing impact velocity and the likelihood for direct impact to the hip, strongly influence fracture risk. One method for reducing the body's impact velocity and kinetic energy during a fall is to absorb energy in the lower extremity muscles during descent, as occurs during sitting and squatting. In the present study, we employed a series of in verted pendulum models to determine: (a) the theoretical effect of this mechanism on impact severity during a backward fall, and (b) the effect on impact severity of age-related declines (or exercise-induced enhancements) in lower extremity strength. Compared to the case of a fall with zero energy absorption in the lower extremity joints, best-case falls (which involved 81 percent activation of ankle and hip muscles, but only 23 percent activation of knees muscles) involved 79 percent attenuation (from 352 J to 74 J) in the body's vertical kinetic energy at impact (KEv), and 48 percent attenuation (from 3.22 to 1.68 m/s) in the downward velocity of the pelvis at impact (v(v)). Among the mechanisms responsible for this were: (1) eccentric contraction of lower extremity muscles during descent, which resulted in up to 150 J of energy absorption; (2) impact with the trunk in an upright configuration, which reduced the change in potential energy associated with the fall by 100 J; and (3) knee extension during the final stage of descent, which "transferred" up to 90 J of impact energy into horizontal (as opposed to vertical) kinetic energy. Declines in joint strength reduced the effectiveness of mechanisms (1) and (3), and thereby increased impact severity However, even with reductions of 80 percent in available torques, KEv was attenuated by 50 percent. This indicates the importance of both technique and strength in reducing impact severity. These results provide motivation for attempts to reduce elderly individuals' risk for fall-related injury through the combination of instruction in safe falling techniques and exercises that enhance lower extremity strength.

Topics: Accidental Falls; Aged; Biomechanical Phenomena; Computer Simulation; Female; Humans; Joints; Leg; Models, Biological; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Nonlinear Dynamics; Posture; Torque

Cross-sectional analytical study in which subjects served as their own controls.. To assess the concentric and eccentric peak torque in the hamstrings and quadriceps muscles, hamstrings/quadriceps amplitude ratios, and lean thigh volume differences in the involved and uninvolved limb of subjects with anterior cruciate ligament (ACL) deficiency.. [corrected] Although the hamstrings/quadriceps ratios for concentric and eccentric activity have been studied, the more functional eccentric hamstings/concentric quadriceps ratio has not been previously described in chronic ACL deficient individuals.. Eighteen subjects (36 +/- 11 years; 12 men, 6 women) with unilateral chronic ACL deficiency were recruited. Changes in activities of daily living, lean thigh volume (LTV) and isokinetic peak torque and total work capacity of both the quadriceps and hamstring muscles were investigated. The uninvolved limb served as control.. Eccentric quadriceps peak torque in the ACL deficient limb was reduced by 38% compared with the 16% reduction of concentric quadriceps peak torque. Eccentric hamstrings peak torque was reduced by 15% compared with an 8% reduction in concentric hamstrings peak torque. LTV in the ACL deficient limb was 11% smaller than the uninvolved limb (3,541 +/- 899 vs 3,161 +/- 742 cc, uninvolved versus ACL deficient limb). The relation between LTV and eccentric peak torque was stronger in the uninvolved (r = 0.82) compared with the ACL deficient limb (r = 0.66). The eccentric hamstrings/quadriceps ratio was significantly higher in the ACL deficient (0.80 +/- 0.26) compared with the uninvolved limb (0.55 +/- 0.13). However, the eccentric hamstrings/concentric quadriceps ratio was similar between ACL deficient (0.75 +/- 0.17) and uninvolved (0.77 +/- 0.20) limbs, while the concentric hamstrings/eccentric quadriceps ratio was significantly higher in the ACL deficient (0.79 +/- 0.26) compared with the uninvolved (0.50 +/- 0.14) limb.. Quadriceps and hamstrings peak torque values were significantly decreased in ACL deficient compared with the uninvolved limb. Eccentric muscle activity was affected to a greater degree than concentric muscle activity in the quadriceps muscle after ACL injury. The eccentric hamstrings/concentric quadriceps ratios were similar in ACL deficient and normal limbs, indicating that muscular co-ordination strategies may have been altered to maintain normal limb activity despite the strength losses particularly evident in quadriceps muscle function.

Topics: Adult; Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Female; Humans; Knee Injuries; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Torque

To examine weakness after stroke, in terms of both level and rate of torque generation.. Descriptive. T tests for dependent and independent samples and Pearson's product moment correlation coefficients were performed.. A rehabilitation unit.. Ten stroke subjects, aged 56 to 81 years, undergoing rehabilitation. Ten neurologically normal subjects aged 55 to 78 years were the controls.. Peak isometric elbow flexor and extensor torque and time to 90% peak elbow flexor and extensor torque at 6 weeks and at 25 weeks after stroke.. At 6 weeks after stroke, subjects were only half as strong and took two to three times longer to produce torque compared to controls (p < or = .05). By 25 weeks after stroke, significant improvements in peak torque (p < or = .02) and time to 90% peak flexor torque (p < or = .05) were seen so that values were within normal limits.. Decreased rate of torque development compounds the problem of reduced peak torque, which may have significant implications for stroke patients, especially in situations where muscles are very weak or where force needs to be generated quickly.

Topics: Aged; Aged, 80 and over; Arm; Cerebrovascular Disorders; Exercise; Female; Functional Laterality; Humans; Male; Middle Aged; Muscle Weakness; Reference Values; Torque

A 5-year prospective study.. To investigate trunk muscle weakness as a risk factor for low back pain in asymptomatic volunteers.. Muscle strength has not been sufficiently studied as a risk factor for low back pain.. The study participants included 30 male and 37 female volunteers (mean age, 17 +/- 2 years), who neither reported nor had ever been treated for low back pain. Trunk muscle strength was measured isokinetically (60 degrees/sec), using the trunk extension and flexion and torso rotation units. The peak torques of the volunteers' extension, flexion, rightward rotation, and leftward rotation were measured, and the agonist/antagonist ratios were calculated as extension/flexion and left rotation/right rotation ratio. The volunteers then were followed prospectively for 5 years to determine the incidence of low back pain and were classified into a non-low back pain group (volunteers with no low back pain during the 5-year follow-up period) and a low back pain group (volunteers who experienced low back pain during this period).. The low back pain group consisted of 8 male and 10 female volunteers. There were no significant differences between the non-low back pain group and the low back pain group regarding age, height, weight, the peak torque values, or the left rotation/right rotation ratio. However, the extension/flexion ratio of the low back pain group (men, 0.96 +/- 0.27; women, 0.77 +/- 0.19) demonstrated significantly lower values than that of the non-low back pain group (1.23 +/- 0.28 and 1.00 +/- 0.16 for men and women, respectively, P < 0.05).. An imbalance in trunk muscle strength, i.e., lower extensor muscle strength than flexor muscle strength, might be one risk factor for low back pain.

Topics: Adolescent; Adult; Female; Humans; Isometric Contraction; Low Back Pain; Lumbosacral Region; Male; Muscle Weakness; Muscle, Skeletal; Prospective Studies; Risk Factors; Torque

We measured isokinetic muscle strength of knee extension and flexion in 18 patients with Parkinson's disease who showed marked laterality in symptom severity and compared strength between the sides in the same patient. In all patient groups, the maximum peak torque of the more affected side was significantly less than for the less affected side at 15 revolutions per minute (r.p.m.) and 30 r.p.m. with the difference between the sides being larger at 30 r.p.m. than at 15 r.p.m., while at 5 r.p.m. there were no significant differences between sides. In the Yahr stage I group, the maximum peak torque in both extension and flexion at each velocity showed no significant difference between the sides. In contrast, in the stage II and III groups the maximum peak torque at 5 r.p.m. showed no significant difference between the sides, while at 15 r.p.m. and 30 r.p.m. these values showed a tendency and a significant difference between the sides, respectively, with the more affected side being weaker. These results suggest that muscle weakness in patients with Parkinson's disease increases with performance velocity, especially as the disease progresses.

Topics: Acceleration; Case-Control Studies; Female; Humans; Leg; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Parkinson Disease; Severity of Illness Index; Time and Motion Studies; Torque; Weight-Bearing

Patients with severe chronic heart failure (CHF) suffer from marked weakness of skeletal muscles. Neuromuscular electrical stimulation (NMES) proved to be an alternative to active strength training. The objective of this study was to test the feasibility and effectiveness of NMES in patients with chronic heart failure. Seven patients (56.0 +/- 5.0 years, CHF for 20 +/- 4 months, left ventricular ejection fraction 20.1 +/- 10.0%) finished an 8 week course of NMES of the knee extensor muscles. The stimulator delivered biphasic, symmetric, constant voltage impulses of 0.7 ms pulse width with a frequency of 50 Hz, 2 s on and 6 s off. No adverse effects occurred. After the stimulation period, the isokinetic peak torque of the knee extensor muscles increased by 13% from 101.0 +/- 8.7 Nm to 113.5 +/- 7.2 Nm (p = 0.004). The maximal isometric strength increased by 20% from 294.3 +/- 19.6 N to 354.14 +/- 15.7 N (p = 0.04). This increased muscle strength could be maintained in a 20 min fatigue test indicating decreased muscle fatigue. These results demonstrate that NMES of skeletal muscles in patients with severe chronic heart failure is a promising method for strength training in this group of patients.

Topics: Chronic Disease; Electric Stimulation Therapy; Evaluation Studies as Topic; Feasibility Studies; Female; Heart Failure; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Muscle Contraction; Muscle Fatigue; Muscle Weakness; Neuromuscular Junction; Range of Motion, Articular; Stroke Volume; Torque; Ventricular Dysfunction, Left

Spinal cord lesions at level C5 to C6 lead to loss of hand functions and lesions at C4 to additional deficits of arm functionality. The presented dual channel surface stimulator with dual channel electromyogram (EMG) measurement was developed to investigate control strategies for an EMG-controlled implantable stimulation system and serves in addition as a therapy device for patients with partial innervation but weak muscle force. Four different control strategies for stimulation amplitude are available. The amplitude can be preset manually or can follow the preprocessed EMG signals proportionally. The shoulder control program allows proportional control of both stimulation channels with one EMG channel while the second EMG channel serves as the channel selector. Finally, a special feedback training program triggers a stimulation burst when EMG activity is detected. During a 2 year patient study, 18 patients from 2 hospitals and 1 rehabilitation center performed the feedback training. Almost all patients obtained an improvement of functionality. Apart from muscle strengthening, the feedback effect led to an improvement of proprioception and supported relearning of motions. For the documentation of the training status, functional muscle test (British Medical Research Council) and measurements of power, angle, torque, muscle fatigue, and EMG were performed. Obviously, EMG triggered stimulation provides several advantages compared to conventional passive electrical stimulation.

Topics: Arm; Brachial Plexus; Electric Stimulation Therapy; Electrodes, Implanted; Electromyography; Feedback; Hemiplegia; Humans; Movement; Muscle Contraction; Muscle Fatigue; Muscle Weakness; Muscle, Skeletal; Paralysis; Proprioception; Shoulder; Spinal Cord Diseases; Torque

To investigate the task dependence of elbow weakness in patients with hemiparesis.. Descriptive study based on interlimb comparisons of maximum voluntary torques (MVTs) generated isometrically in elbow flexion and extension under four task conditions: without explicit control of the torques at adjacent joints and in combination with each of three submaximal shoulder abduction/adduction torque levels.. Rehabilitation center research laboratory.. Volunteer samples of six patients with chronic hemiparesis and four controls.. Residual strength (RS), defined as the ratio of MVTs for the paretic and nonparetic limbs of patients and nondominant and dominant limbs of controls.. For the patient group a significant effect of task condition on RS was found (analysis of variance, p = .0003 and p = .002 for elbow flexion and extension, respectively). With increasing shoulder abduction torque level, elbow flexion RS increased and elbow extension RS decreased. In contrast, for the control group, the effect of task condition on RS was not significant.. In hemiparetic patients, weakness of the paretic elbow musculature shows a strong task dependence. This task dependence likely reflects the existence of abnormal synergies between elbow and shoulder muscles of the paretic limb and has important implications for the rehabilitation of motor function following hemiparesis.

Topics: Adult; Aged; Analysis of Variance; Case-Control Studies; Chronic Disease; Elbow Joint; Female; Functional Laterality; Hemiplegia; Humans; Isometric Contraction; Male; Middle Aged; Muscle Weakness; Predictive Value of Tests; Psychomotor Performance; Range of Motion, Articular; Rotation; Task Performance and Analysis; Torque

Single-group, repeated measures.. To investigate the relationship between tubing length and tubing tension for 6 colors of Thera-Band tubing (each color representing a different level of resistance) and to estimate the resistive shoulder torque provided during shoulder abduction exercise.. Thera-Band tubing is popular for providing resistance in rehabilitation strengthening programs. Unfortunately, it is difficult to compare use of elastic tubing with other resistance training methods because no published data exist on how much resistance is being provided during exercise.. Nine male and 6 female subjects (age, 25.9 +/- 3.6 years; height, 173 +/- 10 cm) performed shoulder abduction, using 6 colors of tubing. A strain gauge attached at the fixed end of the tubing directly measured the tension generated during stretch. For each color of tubing, each subject momentarily held a position at 30 degrees, 60 degrees, 90 degrees, 120 degrees, and 150 degrees of abduction. Shoulder joint abduction, limb segment position, and tubing length were analyzed by means of the Peak Motion Measurement System. Simple linear regression equations predicted tubing tension from percent change in tubing length at the joint angle positions. A 2-way (5 x 6) repeated-measures ANOVA determined the mean differences in tubing tension across tubing colors at the shoulder abduction positions.. Strong linear relationships were found for each tubing tension when referenced according to changes in tubing length. Significant differences in tension were found for the various colors of tubing. The resistive torque curves for each color tubing were similar to isotonic exercise.. Thera-Band tubing provides linear resistance during shoulder abduction, but the resistive torque provided by the tubing mimics isotonic exercise.

Topics: Adult; Biomechanical Phenomena; Equipment Design; Exercise Therapy; Female; Humans; Joint Instability; Male; Muscle Weakness; Shoulder Injuries; Torque; Weight-Bearing

The use of muscle balancing by the clinician to determine return to activity or discharge of a patient is not a well understood measure. Because of the lack of information on the poorly understood concept of eccentric/concentric (E/C) ratios at the ankle, the purpose was to determine the E/C ratios for the invertor and evertor muscles at various velocities in healthy and chronically unstable ankles.. Ten subjects with healthy ankles and 14 with chronically unstable ankles performed five maximal effort reciprocal eccentric/contraction contractions on an isokinetic dynamometer at four velocities (60, 120, 180, and 240 degrees/s) and for each physiological movement of inversion and eversion. Data were analysed using a two way mixed model analysis of variance with repeated measures, with Tukey's test used for post hoc analysis.. Although the chronically unstable ankle was significantly weaker (p < 0.05) eccentrically and concentrically for inversion and eversion, the main effect of the E/C ratios for the ankle was not significant for either joint motion. The main effect of velocity was significant (p < 0.05) for each joint motion, but no significant interaction effects were observed. As velocity increased, the E/C ratio increased, except at 180 and 240 degrees/s for either ankle group.. Chronic ankle instability and muscle weakness co-exist. Adequate E/C ratios in the chronically unstable ankle may exist in the absence of normal strength values.

Topics: Adult; Analysis of Variance; Ankle Joint; Chronic Disease; Female; Humans; Joint Instability; Male; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Range of Motion, Articular; Torque

To evaluate the relation between variability of the torque curves and factors such as age, gender, measurement speeds, and period from low back pain (LBP) onset at isokinetic trunk strength testing.. Observational.. Hospital.. One hundred forty-three consecutive LBP patients (acute, subacute, and chronic) who received physical therapy, and 200 healthy volunteer subjects.. The variability of the torque curves is an indicator of consistency of effort, and was measured as the coefficient of variance (CV) at different measurement speeds in isokinetic trunk flexion/extension strength testing.. The CV was lower in men than in women at the faster measurement speed. LBP patients had higher CV values than healthy subjects. The CV was different according to gender and measurement speed, but not different according to age and periods from LBP onset.. The CV was affected by measurement speed and gender, but not by age or period from LBP onset. Because the CV was higher in LBP patients than in healthy subjects, this value may be usable as an adjunctive index of LBP.

Topics: Abdomen; Acute Disease; Adolescent; Adult; Age Factors; Aged; Aged, 80 and over; Case-Control Studies; Chronic Disease; Female; Humans; Isotonic Contraction; Low Back Pain; Male; Middle Aged; Muscle Weakness; Range of Motion, Articular; Sex Factors; Thorax; Torque

We have previously shown that action tremor persists during maximal wrist extension in patients with Parkinson's disease, and that this contributes to weakness at this joint by preventing the fully fused contraction of the forearm extensor muscles. Antiparkinsonian medication reduces the action tremor in torque and electromyographic (EMG) records, thereby improving strength at the wrist. In the present experiments, peak torque and action tremor were recorded during maximal extension of the elbow in nine patients with Parkinson's disease while they were on and off antiparkinsonian medication, and in eight age- and sex-matched healthy subjects. Peak torque and mean rectified EMG levels were reduced by 34% and 36%, respectively, during maximal elbow extension when patients off medication were compared to those in the treated state. Action tremor was visible in torque records and had a frequency of approximately 10 Hz both in parkinsonian patients and in normal controls. Activity of a similar frequency was often detected in EMG records, especially in patients off therapy. The absolute amplitude of action tremor in torque (A[torque]) and EMG (A[EMG]) records from the elbow was unaffected by therapy and was little different from that recorded in healthy controls. The relative action tremor in torque ([A(torque)/peak torque] x 100) and EMG ([A(EMG)/mean rectified EMG] x 100) was reduced by treatment, but this was the result of the increase in peak torque and mean rectified EMG. Thus, in contrast to the results at the wrist, antiparkinsonian medication has little effect on the 10-Hz action tremor at the elbow. Increased strength is produced by a different mechanism which allows recruitment of triceps motor units outside of this synchronizing influence.

Topics: Aged; Antiparkinson Agents; Case-Control Studies; Elbow Joint; Electromyography; Female; Humans; Longitudinal Studies; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Parkinson Disease; Torque; Tremor

Altered trunk function has been observed in people with Parkinson's disease (PD).. This study investigated the trunk function of people with PD, as compared with people without PD.. Range of motion (against 1 N.m of resistance), isometric torque, and isoinertial performance against moderate resistance were assessed using an Isostation B-200.. Group effects between the subjects with PD and the subjects without PD were found for all variables. Range of motion into extension and maximum and average isometric torque in the directions of extension and right rotation showed group effects between subjects classified as being in Hoehn and Yahr stage I and subjects classified as being in Hoehn and Yahr stage II.. People with PD exhibit less axial range of motion and isometric and isoinertial ability compared with persons without PD. There is a loss of the ability to extend the trunk early in the disease. These findings suggest the importance of further investigation into the role of strengthening programs soon after a diagnosis of PD in order to potentially delay changes in trunk function and subsequent functional difficulties.

Topics: Abdominal Muscles; Aged; Analysis of Variance; Back; Case-Control Studies; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Parkinson Disease; Range of Motion, Articular; Torque

Poor muscle strength, relative to the physical demands of specific jobs, is considered a risk factor for low back pain. To gain an understanding of the underlying mechanisms, this study questioned whether muscle strength was related to task performance and low back load in nursing tasks. Trunk extension, elbow flexion and knee extension strength were therefore measured in 17 nurses. The independent effects of muscle strength on task duration, jerkiness of effort and L5-S1 torque were investigated as the nurses performed several patient handling tasks. Despite a large variation in muscle strength within the subject population, no effect of strength on task duration, jerkiness or L5-S1 torques was observed. In conclusion, poor muscle strength was found not to be related to increased low back load. If 'weaker' nurses were to be at a higher risk, it would be due to a reduced capability to withstand the mechanical load, rather than to an increased mechanical load.

Topics: Adult; Biomechanical Phenomena; Female; Humans; Lifting; Low Back Pain; Male; Muscle Weakness; Nursing Staff; Occupational Diseases; Risk Factors; Task Performance and Analysis; Torque; Workload

Twenty-one subjects with polio 24 to 51 years prior to the first examination were studied on three occasions, each 4 years apart with measurements of muscle strength and endurance for knee extension, macro EMG, and muscle biopsy from vastus lateralis. On average the muscle strength decreased during the 8-year follow-up by 9-15%. Endurance decreased during the observation period. The muscle fiber area was markedly increased in most subjects. There was a decrease in the capillarization during the follow-up. Macro EMG was increased in all subjects (range 3-42 times control) and increased in 20 legs during the 8-year follow-up, but showed a decrease in 8 of 9 legs with an approximative breakpoint when macro MUPs were around 20 times the normal size. Thus, evidence of on-going denervation/reinnervation as well as of failing capacity to maintain large motor units was demonstrated. SFEMG showed a moderate degree of disturbed neuromuscular transmission.

Topics: Adult; Aged; Biopsy; Citrate (si)-Synthase; Electromyography; Female; Humans; Knee Joint; Longitudinal Studies; Male; Middle Aged; Motor Neurons; Muscle Contraction; Muscle Fibers, Skeletal; Muscle Weakness; Muscle, Skeletal; Physical Endurance; Poliomyelitis; Torque

To determine the relation of hamstring and quadriceps muscle strength and imbalance to hamstring injury using a prospective observational cohort study. A total of 102 senior male Australian Rules footballers aged 22.2 (3.6) years were tested at the start of a football season. Maximum voluntary concentric and eccentric torque of the hamstring and quadriceps muscles of both legs was assessed using a Kin-Com isokinetic dynamometer at angular velocities of 60 and 180 degrees/second. Twelve (11.8%) players sustained clinically diagnosed hamstring strains which caused them to miss one or more matches over the ensuing season.. There were no significant differences for any of the isokinetic variables comparing the injured and non-injured legs in players with unilateral hamstring strains (n=9). Neither the injured nor the non-injured leg of injured players differed from the mean of left and right legs in non-injured players for any isokinetic variable. The hamstring to opposite hamstring ratios also did not differ between injured and non-injured players. A hamstring to opposite hamstring ratio of less than 0.90 and a hamstring to quadriceps ratio of less than 0.60 were not associated with an increased risk of hamstring injury. A significantly greater percentage of players who sustained a hamstring strain reported a history of hamstring strain compared with non-injured players (p=0.02). However, this was not related to muscle weakness or imbalance.. Isokinetic muscle strength testing was not able to directly discriminate Australian Rules football players at risk for a hamstring injury.

Topics: Adult; Australia; Cohort Studies; Football; Forecasting; Humans; Male; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Prospective Studies; Recurrence; Risk Factors; Sprains and Strains; Tendon Injuries; Tendons; Torque

Topics: Cerebrovascular Disorders; Ergometry; Functional Laterality; Humans; Motor Cortex; Muscle Contraction; Muscle Weakness; Physical Exertion; Torque

The aim of this study was to see whether action tremor contributes to the weakness which can be measured in some muscles in patients with Parkinson's disease, by preventing fully fused contraction of motor units. Strength and action tremor were recorded during maximal wrist extension in patients when they were on and off antiparkinsonian medication, and in age- and sex-matched healthy subjects. Peak torque and mean rectified EMG levels were reduced by 25% and 30% (n = 7), respectively, when patients were off medication (compared with when they were on medication). In parkinsonian patients off treatment, action tremor was visible in torque and EMG records, and had a frequency of approximately 10 Hz. The absolute amplitude of this tremor was considerably smaller in patients on medication and in control subjects. In patients, medication reduced action tremor in torque and EMG by 37% and 57%, respectively, so that tremor amplitude approached that in normals. Similar changes were seen when action tremor was expressed as % peak torque of % mean rectified EMG. In parkinsonian patients off medication, a 10-Hz synchronizing influence dominates muscle activity at the wrist. The results is an incompletely fused muscle contraction, which is an important factor contributing to the weakness present in the off-medication state. Antiparkinsonian medication releases motor units from the 10-Hz synchronizing influence, enabling higher discharge rates, fused contraction and improved force generation.

Topics: Aged; Electromyography; Electrophysiology; Humans; Male; Middle Aged; Muscle Weakness; Parkinson Disease; Torque; Tremor

To compare strength and endurance variables obtained in the quadriceps muscles of postpolio and control subjects over a 7-year interval with macro and single fiber electromyography (EMG) variables.. A controlled inception cohort study.. Neuromuscular research laboratory of a university hospital.. A cohort of 23 postpolio and 14 control subjects. All postpolio subjects had a history, physical examination, and EMG consistent with previous poliomyelitis, and had greater than antigravity strength in the quadriceps muscle tested. Unstable postpolio subjects acknowledged new quadriceps weakness over the 7-year period of the study (n = 11), and stable postpolio subjects denied new weakness of the quadriceps over the same period (n = 12).. All subjects had tests of neuromuscular function of the quadriceps muscles at the onset of this study and yearly over a 7-year period. EMG variables were determined on a separate day after the seventh year of neuromuscular measurements. Neuromuscular variables measured were isometric knee extension peak torque, isometric endurance (time to inability to maintain knee extensor contraction at 40% of maximal torque), tension time index (TTI) (product of isometric endurance time and 40% of maximal torque), and recovery of torque at 10 minutes after the endurance test. EMG variables were macro EMG and single fiber EMG (jitter, fiber density, and percent blocking).. Unstable postpolio subjects did not lose strength more rapidly than stable postpolio subjects or control subjects. Unstable postpolio subjects were significantly weaker, had decreased TTI, larger macro EMG amplitude, greater jitter, blocking, and fiber density in comparison with stable postpolio subjects (all p < .05). Strength was negatively correlated with macro EMG amplitude in the stable postpolio group (p < .05). The slope of the regression line of strength over 7 years did not correlate (p > .05) with neuromuscular or EMG variables in control, stable, or unstable postpolio subjects.

Topics: Age of Onset; Case-Control Studies; Disease Progression; Electromyography; Female; Humans; Isometric Contraction; Longitudinal Studies; Male; Middle Aged; Muscle Weakness; Physical Endurance; Postpoliomyelitis Syndrome; Regression Analysis; Time Factors; Torque

The purpose of this investigation was to determine the influence of pain and muscle weakness on gait variables in subjects with patellofemoral pain (PFP).. Nineteen female subjects with a diagnosis of PFP and 19 female subjects without PFP participated in the study.. Subjects underwent gait analysis (stride characteristics and joint motion) during level walking, ascending and descending stairs, and ascending and descending ramps, in addition to isometric torque testing of the knee extensors of the involved limb. Pain and functional status also were assessed.. Compared with the comparison group, the primary gait compensation in the PFP group was a reduced walking speed, which was a function of both a reduced stride length and cadence. Knee extensor torque was the only predictor of gait function, with increased torque correlating with improved stride characteristics. In addition, PFP was not associated with locomotor function.. These findings suggest that functional ability in persons with PFP is associated with increased quadriceps femoris muscle torque. Future research is needed to determine whether function improves with quadriceps femoris muscle strengthening.

Topics: Adolescent; Adult; Female; Gait; Humans; Knee Joint; Middle Aged; Muscle Weakness; Muscle, Skeletal; Pain; Thigh; Torque