Biomechanic changes in passive properties of hemiplegic ankles with spastic hypertonia11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

Developing a multi-joint upper limb exoskeleton robot for diagnosis, therapy, and outcome evaluation in neurorehabilitation

Arm impairments in patients post stroke involve the shoulder, elbow and wrist simultaneously. It is not very clear how patients develop spasticity and reduced range of motion (ROM) at the multiple joints and the abnormal couplings among the multiple joints and the multiple degrees-of-freedom (DOF) during passive movement. It is also not clear how they lose independent control of individual joints/DOFs and coordination among the joints/DOFs during voluntary movement. An upper limb exoskeleton robot, the IntelliArm, which can control the shoulder, elbow, and wrist, was developed, aiming to support clinicians and patients with the following integrated capabilities: 1) quantitative, objective, and comprehensive multi-joint neuromechanical pre-evaluation capabilities aiding multi-joint/DOF diagnosis for individual patients; 2) strenuous and safe passive stretching of hypertonic/deformed arm for loosening up muscles/joints based on the robot-aided diagnosis; 3) (assistive/resistive) active reaching training after passive stretching for regaining/improving motor control ability; and 4) quantitative, objective, and comprehensive neuromechanical outcome evaluation at the level of individual joints/DOFs, multiple joints, and whole arm. Feasibility of the integrated capabilities was demonstrated through experiments with stroke survivors and healthy subjects.

Changes of Reflex, Non-reflex and Torque Generation Properties of Spastic Ankle Plantar Flexors Induced by Intelligent Stretching

Spasticity, contracture, and muscle weakness are major sources of disability in stroke. Changes of torque-generating capacity as well as reflex and non-reflex properties of ankle plantar flexors induced by strenuous stretching in chronic hemiplegia were investigated. Twelve subjects with a unilateral stroke and 10 healthy controls underwent 30 minutes of strenuous intelligent stretching treatment. Reflex and non-reflex components of spastic hypertonia and force-generating capacity of ankle plantar flexors were investigated. Dorsiflexion (DF) range of motion (ROM) was increased (p=0.002) and passive stiffness and passive resistant torque of the spastic muscles were decreased (p=0.004 and 0.007, respectively), while reflex hyper-excitability diminished slightly but with no statistical significance. The maximal voluntary contraction (MVC) torque of the spastic ankle plantar flexors was increased after the forceful stretching treatment (p=0.041). In contrast, the stretching treatment of the healthy plantar flexors did not change any of the variables measured before and after stretching. The stroke subjects who gained more DF ROM or larger decrement of stiffness achieved greater increment of the peak torque generation after the stretching (r=0.597 with p=0.040 and r=-0.746 with p=0.005, respectively). These results suggest that the strenuous dynamic stretching could improve the force-generating capacity of spastic muscles as well as reduce the passive stiffness and increase ROM.

Static ankle impedance in stroke and multiple sclerosis: a feasibility study

Quantitative characterization of ankle mechanical impedance is critical for understanding lower extremity function in persons with neurological disorders. In this paper, we examine the feasibility of employing an ankle robot and multivariable analysis to determine static ankle impedance in 4 patients: 1 with multiple sclerosis and 3 with stroke. We employed a scalar based vector field approximation method which was successful in identifying young healthy subjects' ankle impedance. It enabled clear interpretation of spatial ankle impedance structure and intermuscular feedback at the ankle for both affected and unaffected legs. Measured impedance of two patients was comparable to healthy young subjects, while the other two patients had significantly different static ankle impedance properties.

Passive mechanical properties of gastrocnemius muscles of people with ankle contracture after stroke

OBJECTIVE

To investigate the mechanisms of contracture after stroke by comparing passive mechanical properties of gastrocnemius muscle-tendon units, muscle fascicles, and tendons in people with ankle contracture after stroke with control participants.

DESIGN

Cross-sectional study.

SETTING

Laboratory in a research institution.

PARTICIPANTS

A convenience sample of people with ankle contracture after stroke (n=20) and able-bodied control subjects (n=30).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Stiffness and lengths of gastrocnemius muscle-tendon units, lengths of muscle fascicles, and tendons at specific tensions.

RESULTS

At a tension of 100N, the gastrocnemius muscle-tendon unit was significantly shorter in participants with stroke (mean, 436mm) than in able-bodied control participants (mean, 444mm; difference, 8mm; 95% confidence interval [CI], 0.2-15mm; P=.04). Muscle fascicles were also shorter in the stroke group (mean, 44mm) than in the control group (mean, 50mm; difference, 6mm; 95% CI, 1-12mm; P=.03). There were no significant differences between groups in the mean stiffness or length of the muscle-tendon units and fascicles at low tension, or in the mean length of the tendons at any tension.

CONCLUSIONS

People with ankle contracture after stroke have shorter gastrocnemius muscle-tendon units and muscle fascicles than control participants at high tension. This difference is not apparent at low tension.

Diminished capacity to modulate motor activation patterns according to task contributes to thumb deficits following stroke

The objective of this study was to explore motor impairment of the thumb following stroke. More specifically, we quantitatively examined kinetic deficits of the thumb. We anticipated that force deficits would be nonuniformly distributed across the kinetic workspace, due in part to varying levels of difficulty in altering the motor activation pattern to meet the task. Eighteen stroke survivors with chronic hemiparesis participated in the trials, along with nine age-matched controls. Of the stroke-survivor group, nine subjects had moderate hand impairment, and the other nine subjects had severe hand impairment. Subjects were instructed to generate maximal isometric thumb-tip force, as measured with a load cell, in each of six orthogonal directions with respect to the thumb tip. Activity of three representative thumb muscles was monitored through intramuscular and surface electrodes. Univariate split-plot analysis of variance revealed that clinical impairment level had a significant effect on measured force (P < 0.001), with the severely impaired group producing only 13% of the control forces, and the moderately impaired group generating 32% of control forces, on average. Weakness in the moderately impaired group exhibited a dependence on force direction (P = 0.015), with the least-relative weakness in the medial direction. Electromyographic recordings revealed that stroke survivors exhibited limited modulation of thumb-muscle activity with intended force direction. The difference in activation presented by the control group for a given muscle was equal to 40% of its full activation range across force directions, whereas this difference was only 26% for the moderately impaired group and 15% for the severely impaired group. This diminished ability to modify voluntary activation patterns, which we observed previously in index-finger muscles as well, appears to be a primary factor in hand impairment following stroke.

Effects of repeated ankle stretching on calf muscle-tendon and ankle biomechanical properties in stroke survivors

BACKGROUND

The objective of this study was to investigate changes in active and passive biomechanical properties of the calf muscle-tendon unit induced by controlled ankle stretching in stroke survivors.

METHODS

Ten stroke survivors with ankle spasticity/contracture and ten healthy control subjects received intervention of 60-min ankle stretching. Joint biomechanical properties including resistance torque, stiffness and index of hysteresis were evaluated pre- and post-intervention. Achilles tendon length was measured using ultrasonography. The force output of the triceps surae muscles was characterized via the torque-angle relationship, by stimulating the calf muscles at a controlled intensity across different ankle positions.

FINDINGS

Compared to healthy controls, the ankle position corresponding to the peak torque of the stroke survivors was shifted towards plantar flexion (P<0.001). Stroke survivors showed significantly higher resistance torques and joint stiffness (P<0.05), and these higher resistances were reduced significantly after the stretching intervention, especially in dorsiflexion (P=0.013). Stretching significantly improved the force output of the impaired calf muscles in stroke survivors under matched stimulations (P<0.05). Ankle range of motion was also increased by stretching (P<0.001).

INTERPRETATION

At the joint level, repeated stretching loosened the ankle joint with increased passive joint range of motion and decreased joint stiffness. At the muscle-tendon level, repeated stretching improved calf muscle force output, which might be associated with decreased muscle fascicle stiffness, increased fascicle length and shortening of the Achilles tendon. The study provided evidence of improvement in muscle tendon properties through stretching intervention.

Multivariable static ankle mechanical impedance with relaxed muscles

Quantitative characterization of ankle mechanical impedance is important to understand how the ankle supports lower-extremity functions during interaction with the environment. This paper reports a novel procedure to characterize static multivariable ankle mechanical impedance. An experimental protocol using a wearable therapeutic robot, Anklebot, enabled reliable measurement of torque and angle data in multiple degrees of freedom simultaneously, a combination of inversion-eversion and dorsiflexion-plantarflexion. The measured multivariable torque-angle relation was represented as a vector field, and approximated using a method based on thin-plate spline smoothing with generalized cross validation. The vector field enabled assessment of several important characteristics of static ankle mechanical impedance, which are not available from prior single degree of freedom studies: the directional variation of ankle mechanical impedance, the extent to which the ankle behaves as a spring, and evidence of uniquely neural contributions. The method was validated by testing a simple physical "mock-up" consisting of passive elements. Experiments with young unimpaired subjects quantified the behavior of the maximally relaxed human ankle, showing that ankle mechanical impedance is spring-like but strongly direction-dependent, being weakest in inversion. Remarkably, the analysis was sufficiently sensitive to detect a subtle but statistically significant deviation from spring-like behavior if subjects were not fully relaxed. This method may provide new insight about the function of the ankle, both unimpaired and after biomechanical or neurological injury.

Measurement of passive ankle stiffness in subjects with chronic hemiparesis using a novel ankle robot

Our objective in this study was to assess passive mechanical stiffness in the ankle of chronic hemiparetic stroke survivors and to compare it with those of healthy young and older (age-matched) individuals. Given the importance of the ankle during locomotion, an accurate estimate of passive ankle stiffness would be valuable for locomotor rehabilitation, potentially providing a measure of recovery and a quantitative basis to design treatment protocols. Using a novel ankle robot, we characterized passive ankle stiffness both in sagittal and in frontal planes by applying perturbations to the ankle joint over the entire range of motion with subjects in a relaxed state. We found that passive stiffness of the affected ankle joint was significantly higher in chronic stroke survivors than in healthy adults of a similar cohort, both in the sagittal as well as frontal plane of movement, in three out of four directions tested with indistinguishable stiffness values in plantarflexion direction. Our findings are comparable to the literature, thus indicating its plausibility, and, to our knowledge, report for the first time passive stiffness in the frontal plane for persons with chronic stroke and older healthy adults.

Combined Passive Stretching and Active Movement Rehabilitation of Lower-Limb Impairments in Children With Cerebral Palsy Using a Portable Robot

Background. Ankle impairments are closely associated with functional limitations in children with cerebral palsy (CP). Passive stretching is often used to increase the range of motion (ROM) of the impaired ankle. Improving motor control is also a focus of physical therapy. However, convenient and effective ways to control passive stretching and motivate active movement training with quantitative outcomes are lacking. Objective. To investigate the efficacy of combined passive stretching and active movement training with motivating games using a portable rehabilitation robot. Methods. Twelve children with mild to moderate spastic CP participated in robotic rehabilitation 3 times per week for 6 weeks. Each session consisted of 20 minutes of passive stretching followed by 30 minutes of active movement training and ended with 10 minutes of passive stretching. Passive ROM (PROM), active ROM (AROM), dorsiflexor and plantarflexor muscle strength, Selective Control Assessment of the Lower Extremity, and functional outcome measures (Pediatric Balance Scale, 6-minute walk, and Timed Up-and-Go) were evaluated before and after the 6-week intervention. Results. Significant increases were observed in dorsiflexion PROM ( P = .002), AROM ( P = .02), and dorsiflexor muscle strength ( P = .001). Spasticity of the ankle musculature was significantly reduced ( P = .01). Selective motor control improved significantly ( P = .005). Functionally, participants showed significantly improved balance ( P = .0025) and increased walking distance within 6 minutes ( P = .025). Conclusions. Passive stretching combined with engaging in active movement training was of benefit in this pilot study for children with CP. They demonstrated improvements in joint biomechanical properties, motor control performance, and functional capability in balance and mobility.

Reliability of the intelligent stretching device for ankle stiffness measurements in healthy individuals

BACKGROUND

A number of devices have been developed to measure joint stiffness. This study investigated the reliability of the Intelligent (Intel) stretch device to measure bilateral ankle joint stiffness during passive range of motion (ROM).

METHODS

The reliability of the device was investigated based on torque and angle by establishing the consistency of measurements between examiners on different testing days. In addition, demographic variables were analyzed to investigate the degree of stiffness. Forty-six gender-matched subjects completed the test.

RESULTS

The reliability ICC₂(,)₁ coefficient of ankle stiffness between-day for both examiners was 0.77 for the right ankle and 0.76 for the left ankle with a 0.05 standard error of measurement (SEM) for ankle stiffness for the right side and 0.04 for the left side. The ICC values of the two examiners were also high based on Chronbach's alpha (0.87 and 0.86). Among the demographic variables, gender (F=35.25, p=0.001) and body weight (F=23.55, p=0.001) were the most important factors in determining ankle joint stiffness.

DISCUSSION

The results of this study indicated that dorsiflexion and plantarflexion measurements obtained by the Intel stretch device are reproducible and consistent. In addition, ankle stiffness was significantly different based on gender and body weight to develop and/or maintain ankle function. These results may help to identify ankle stiffness factors that will lead to more efficient rehabilitation programs and injury prevention strategies.

Design of an automated device to measure sagittal plane stiffness of an articulated ankle-foot orthosis

The purpose of this study was to design a new automated stiffness measurement device which could perform a simultaneous measurement of both dorsi- and plantarflexion angles and the corresponding resistive torque around the rotational centre of an articulated ankle-foot orthosis (AAFO). This was achieved by controlling angular velocities and range of motion in the sagittal plane. The device consisted of a hydraulic servo fatigue testing machine, a torque meter, a potentiometer, a rotary plate and an upright supporter to enable an AAFO to be attached to the device via a surrogate shank. The accuracy of the device in reproducing the range of motion and angular velocity was within 4% and 1% respectively in the range of motion of 30° (15° plantarflexion to 15° dorsiflexion) at the angular velocity of 10°/s, while that in the measurement of AAFO torque was within 8% at the 0° position. The device should prove useful to assist an orthotist or a manufacturer to quantify the stiffness of an AAFO and inform its clinical use.

Characterization of spasticity in cerebral palsy: dependence of catch angle on velocity

AIM

To evaluate spasticity under controlled velocities and torques in children with cerebral palsy (CP) using a manual spasticity evaluator.

METHOD

The study involved 10 children with spastic CP (six males, four females; mean age 10 y 1 mo, SD 2 y 9 mo, range 7-16 y; one with quadriplegia, six with right hemiplegia, three with left hemiplegia; Gross Motor Function Classification System levels I [n=2], II [n=3], III [n=2], IV [n=2], and V [n=1]; Manual Ability Classification System levels II [n=5], III [n=4], and V [n=1]) and 10 typically developing participants (four males, six females; mean age 10 y 3 mo, SD 2 y 7 mo, range 7-15 y). Spasticity and catch angle were evaluated using joint position, resistance torque, and torque rate at velocities of 90 degrees, 180 degrees, and 270 degrees per second, controlled using real-time audio-visual feedback. Biomechanically, elbow range of motion (ROM), stiffness, and energy loss were determined during slow movement (30 degrees/s) and under controlled terminal torque.

RESULTS

Compared with typically developing children, children with CP showed higher reflex-mediated torque (p<0.001) and the torque increased more rapidly with increasing velocity (p<0.001). Catch angle was dependent on velocity and occurred later with increasing velocity (p=0.005). Children with CP showed smaller ROM (p<0.05), greater stiffness (p<0.001), and more energy loss (p=0.003).

INTERPRETATION

Spasticity with velocity dependence may also be position-dependent. The delayed catch angle at higher velocities indicates that the greater resistance felt by the examiner at higher velocities was also due to position change, because the joint was moved further to a stiffer position at higher velocities.

Changes in preferred postural patterns following stroke during intentional ankle/hip coordination

We compared the spatio-temporal postural organization between stroke patients and healthy controls in a bipedal standing task where participants had to intentionally produce two specific ankle/hip coordination patterns: in-phase and anti-phase. The pattern to reproduce was visually represented by a ankle-hip Lissajous figure, and a real-time biofeedback displayed the current coordination sur-imposed to the expected coordination. Contrary to the healthy participants who were successful at reproducing the two patterns, stroke patients were unable to produce the in-phase pattern. In addition, when the anti-phase pattern was required, a reduction of stability was observed for the stroke group. The impairment of postural capacities following stroke was thus accompanied by a disappearance of one of the two preferred patterns found in healthy participants, a result that have consequences for understanding the etiology of postural pattern formation and the elaboration of rehabilitation programs.

Impact of talar component rotation on contact pressure after total ankle arthroplasty: a cadaveric study

BACKGROUND

There is limited literature available to assess the impact of talar component rotation on total ankle contact biomechanics.

MATERIALS AND METHODS

Six male cadaveric below-knee specimens were implanted with Agility(R) total ankles. The sequence of talar rotation for each specimen was randomized between: Neutral, 7.5 degrees internal and 7.5 degrees external rotation. Contact pressure was measured using Tekscan ankle sensors during sequential static axial loadings and 10 simulated dynamic strides under 650 N axial load.

RESULTS

The peak pressure (PP) increased for the internally (PP(static)=7.0 +/- 0.27 MPa (mean +/- SD), p < 0.001; PP(dynamic)=7.8 +/- 0.22 MPa, p = 0.001) and externally rotated talar component positions (PP(static)=6.2 +/- 0.22 MPa, p = 0.011; PP(dynamic)=7.6 +/- 0.29 MPa, p = 0.004) as compared to neutral (PP(static) =5.5 +/- 0.13 MPa; PP(dynamic) = 6.3 +/- 0.11 MPa). The contact area under 650 approximately N load was reduced for both talar component internal (97.38 +/- 17.7 mm(2), p = 0.001) and external rotation (152.66 +/- 16.8 mm(2), p = 0.022) as compared to neutral (190.02 +/- 13.8 mm(2)). There was a significant rotational torque for the malrotated talar components as compared to neutral, that increased with axial loading (p = 0.044).

CONCLUSION

Near the extremes of talar malrotation, there was a consistent change from a continuous tibiotalar contact area to a pattern of two-point contact; the orientation of which opposed the direction of talar component malrotation. Talar component malrotation resulted in: increased peak pressure, decreased contact area and increased rotational torque that resisted the malrotation.

CLINICAL RELEVANCE

Talar component malrotation may contribute to premature polyethylene wear as well as potential talar loosening secondary to the rotational torque generated as the geometry of the prosthesis attempts to seek congruency.

Changes in passive mechanical properties of the gastrocnemius muscle at the muscle fascicle and joint levels in stroke survivors

OBJECTIVES

To investigate the ankle joint-level and muscle fascicle-level changes and their correlations in stroke survivors with spasticity, contracture, and/or muscle weakness at the ankle.

DESIGN

To investigate the fascicular changes of the medial gastrocnemius muscle using ultrasonography and the biomechanical changes at the ankle joint across 0 degrees, 30 degrees, 60 degrees, and 90 degrees knee flexion in a case-control manner.

SETTING

Research laboratory in a rehabilitation hospital.

PARTICIPANTS

Stroke survivors (n=10) with ankle spasticity/contracture and healthy control subjects (n=10).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASUREMENTS

At the muscle fascicle level, medial gastrocnemius muscle architecture including the fascicular length, pennation angle, and thickness were evaluated in vivo with the knee and ankle flexion changed systematically. At the joint level, the ankle range of motion (ROM) and stiffness were determined across the range of 0 degrees to 90 degrees knee flexion.

RESULTS

At comparable joint positions, stroke survivors showed reduced muscle fascicle length, especially in ankle dorsiflexion (P< or =.048) and smaller pennation angle, especially for more extended knee positions (P< or =.049) than those of healthy control subjects. At comparable passive gastrocnemius force, stroke survivors showed higher fascicular stiffness (P< or =.044) and shorter fascicle length (P< or =.025) than controls. The fascicle-level changes of decreased muscle fascicle length and pennation angle and increased medial gastrocnemius fascicle stiffness in stroke were correlated with the joint level changes of increased joint stiffness and decreased ROM (P<.05).

CONCLUSIONS

This study evaluated specific muscle fascicular changes as mechanisms underlying spasticity, contracture, and joint-level impairments, which may help improve stroke rehabilitation and outcome evaluation.

Multichannel SEMG in clinical gait analysis: a review and state-of-the-art

BACKGROUND

Application of surface electromyography (SEMG) to the clinical evaluation of neuromuscular disorders can provide relevant "diagnostic" contributions in terms of nosological classification, localization of focal impairments, detection of pathophysiological mechanisms, and functional assessment.

METHODS

The present review article elaborates on: (i) the technical aspects of the myoelectric signals acquisition within a protocol of clinical gait analysis (multichannel recording, surface vs. deep probes, electrode placing, encumbrance effects), (ii) the sequence of procedures for the subsequent data processing (filtering, averaging, normalization, repeatability control), and (iii) a set of feasible strategies for the final extraction of clinically useful information.

FINDINGS

Relevant examples of SEMG application to functional diagnosis are provided.

INTERPRETATION

Emphasis is given to the key role of SEMG along with kinematic and kinetic analysis, for non-invasive assessment of relevant pathophysiological mechanisms potentially hindering the gait function, such as changes in passive muscle-tendon properties (peripheral non-neural component), paresis, spasticity, and loss of selectivity of motor output in functionally antagonist muscles.

Ultrasonic evaluations of Achilles tendon mechanical properties poststroke

Spasticity, contracture, and muscle weakness are commonly observed poststroke in muscles crossing the ankle. However, it is not clear how biomechanical properties of the Achilles tendon change poststroke, which may affect functions of the impaired muscles directly. Biomechanical properties of the Achilles tendon, including the length and cross-sectional area, in the impaired and unimpaired sides of 10 hemiparetic stroke survivors were evaluated using ultrasonography. Elongation of the Achilles tendon during controlled isometric ramp-and-hold and ramping up then down contractions was determined using a block-matching method. Biomechanical changes in stiffness, Young's modulus, and hysteresis of the Achilles tendon poststroke were investigated by comparing the impaired and unimpaired sides of the 10 patients. The impaired side showed increased tendon length (6%; P = 0.04), decreased stiffness (43%; P < 0.001), decreased Young's modulus (38%; P = 0.005), and increased mechanical hysteresis (1.9 times higher; P < 0.001) compared with the unimpaired side, suggesting Achilles tendon adaptations to muscle spasticity, contracture, and/or disuse poststroke. In vivo quantitative characterizations of the tendon biomechanical properties may help us better understand changes of the calf muscle-tendon unit as a whole and facilitate development of more effective treatments.

The short term effect of cyclic passive stretching on plantarflexor resistive torque after acquired brain injury

BACKGROUND

Increased calf muscle stiffness is a common impairment following acquired brain injury. This study examined the immediate effects of cyclic ankle stretching at two stretch velocities on calf stiffness in individuals with hemiparesis (n=17) and control subjects (n=10).

METHODS

Cyclic ankle stretching was applied for 3min at velocities of 5 degrees s(-1) and 25 degrees s(-1) using a purpose-built dynamometer. Surface electromyography was employed to ensure stretches were passive. Peak plantarflexor resistive torque was derived from torque-angle curves. Comparisons were made between groups, velocities, and between limbs for hemiparetic subjects.

FINDINGS

At baseline, mean peak plantarflexor resistive torque was greater in the affected limbs of hemiparetic subjects than their contralateral limbs (P<0.001), however there was no significant difference between groups. Plantarflexor resistive torque was reduced in all limbs following cyclic stretching regardless of stretch velocity (P<0.005). Two distinct patterns of response were observed in hemiparetic subjects. In nine cases the affected limb responses did not differ from the contralateral limb or control data. In the remaining eight cases mean peak plantarflexor resistive torque in the affected limb was greater than the contralateral limb and control values. In this subgroup, peak plantarflexor resistive torque was significantly affected by stretch velocity and showed the greatest reduction following cyclic stretching.

INTERPRETATION

Cyclic stretching has been shown to produce a short term reduction in calf stiffness in a subgroup of individuals with hemiplegia. Further investigation is required to elaborate the characteristics of those most likely to respond optimally to this intervention.

Altered contractile properties of the gastrocnemius muscle poststroke

Spasticity, contracture and muscle weakness often occur together poststroke and cause considerable motor impairments to stroke survivors. The underlying changes in contractile properties of muscle fascicles are still not clear. The purpose of this study was to investigate the contractile property changes of the medial gastrocnemius muscle fascicles poststroke. Ten stroke survivors and ten healthy subjects participated in the study. The medial gastrocnemius fascicular length was measured at various combinations of ankle and knee positions using ultrasonography, with the muscle activated selectively using electrical stimulation. The stimulation intensity was kept constant across different ankle and knee positions to establish the active force-length relationship of the muscle fascicles. It was found that stroke survivors showed a shift of the force-length curve with a significantly shorter optimal fascicle length (33.2 +/- 3.2 mm) compared with that of healthy controls (47.4 +/- 2.7 mm) with P < 0.001. Furthermore, the width span of the fascicular force-length curve of stroke survivors was significantly narrower with steeper slopes than that of controls (P <or= 0.001), suggesting reduced number of sarcomeres along the fascicles and/or reduced sarcomere length poststroke. Regression analysis showed that the medial gastrocnemius fascicular length of stroke survivors varied significantly less with ankle and knee flexions (P <or= 0.001) than that of controls, suggesting shorter and stiffer muscle fascicles poststroke, which might be attributed to muscle architectural adaptation. This study showed that there are considerable changes in the contractile properties of muscle fascicles poststroke, which may contribute directly to the joint-level changes of decreased range of motion, increased stiffness, muscle weakness, and impaired motor functions in stroke survivors.

Effects of stretching and heat treatment on hamstring extensibility in children with severe mental retardation and hypertonia

Objectives: To examine the effect of heat and duration of stretching on the extensibility of hamstring muscles and their electromyographic responses to passive stretch in children with hypertonia and severe mental retardation.

Design: Randomized cross-over trial.

Setting: Developmental disability unit in a local hospital.

Participants: Twenty-nine subjects (9 females) with ages ranged from 4 to 13 years with spastic and/or dystonic hypertonia and hamstring tightness.

Interventions: Subjects received four treatment sessions in random order with each consisting of five repetitions of stretching: (A) 10-second stretching, (B) 30-second stretching, (C) hot pack followed by 10-second stretching, and (D) hot pack followed by 30-second stretching. Each treatment session comprised five repetitions of stretch and successive treatments were separated by at least 24 hours.

Main outcome measures: The distance between greater trochanter and lateral malleolus and hamstring electromyographic (EMG) activity during passive knee extension stretching.

Results: Two-way ANOVA showed a larger increase in hamstring extensibility in conditions C and D (1.3 ± 1.1 cm) than conditions A and B (0.7 ± 0.9 cm) (P<0.001). For the EMG recordings, conditions B and D (-25.1 ± 58.4μV) had greater decrease than conditions A and C (-3.5 ± 36.6 μV) (P= 0.039).

Conclusions: Heat application to the hamstrings before stretching could result in greater increase in extensibility than stretching alone in children with hypertonia and severe mental retardation. Stretching could promote relaxation of the hamstring muscles regardless of prior heat treatment. Stretching sustained for 30 seconds led to greater relaxation than that for 10 seconds.

Abnormal joint torque patterns exhibited by chronic stroke subjects while walking with a prescribed physiological gait pattern

Background

It is well documented that individuals with chronic stroke often exhibit considerable gait impairments that significantly impact their quality of life. While stroke subjects often walk asymmetrically, we sought to investigate whether prescribing near normal physiological gait patterns with the use of the Lokomat robotic gait-orthosis could help ameliorate asymmetries in gait, specifically, promote similar ankle, knee, and hip joint torques in both lower extremities. We hypothesized that hemiparetic stroke subjects would demonstrate significant differences in total joint torques in both the frontal and sagittal planes compared to non-disabled subjects despite walking under normal gait kinematic trajectories.

Methods

A motion analysis system was used to track the kinematic patterns of the pelvis and legs of 10 chronic hemiparetic stroke subjects and 5 age matched controls as they walked in the Lokomat. The subject's legs were attached to the Lokomat using instrumented shank and thigh cuffs while instrumented footlifters were applied to the impaired foot of stroke subjects to aid with foot clearance during swing. With minimal body-weight support, subjects walked at 2.5 km/hr on an instrumented treadmill capable of measuring ground reaction forces. Through a custom inverse dynamics model, the ankle, knee, and hip joint torques were calculated in both the frontal and sagittal planes. A single factor ANOVA was used to investigate differences in joint torques between control, unimpaired, and impaired legs at various points in the gait cycle.

Results

While the kinematic patterns of the stroke subjects were quite similar to those of the control subjects, the kinetic patterns were very different. During stance phase, the unimpaired limb of stroke subjects produced greater hip extension and knee flexion torques than the control group. At pre-swing, stroke subjects inappropriately extended their impaired knee, while during swing they tended to abduct their impaired leg, both being typical abnormal torque synergy patterns common to stroke gait.

Conclusion

Despite the Lokomat guiding stroke subjects through physiologically symmetric kinematic gait patterns, abnormal asymmetric joint torque patterns are still generated. These differences from the control group are characteristic of the hip hike and circumduction strategy employed by stroke subjects.

Lower extremity passive range of motion in community-ambulating stroke survivors

BACKGROUND

Physical therapists may prescribe stretching exercises for individuals with stroke to improve joint integrity and to reduce the risk of secondary musculoskeletal impairment. While deficits in passive range of motion (PROM) exist in stroke survivors with severe hemiparesis and spasticity, the extent to which impaired lower extremity PROM occurs in community-ambulating stroke survivors remains unclear. This study compared lower extremity PROM in able-bodied individuals and independent community-ambulatory stroke survivors with residual stroke-related neuromuscular impairments. Our hypothesis was that the stroke group would show decreased lower extremity PROM in the paretic but not the nonparetic side and that decreased PROM would be associated with increased muscle stiffness and decreased muscle length.

METHODS

Individuals with chronic poststroke hemiparesis who reported the ability to ambulate independently in the community (n = 17) and age-matched control subjects (n = 15) participated. PROM during slow (5 degrees/sec) hip extension, hip flexion, and ankle dorsiflexion was examined bilaterally using a dynamometer that measured joint position and torque. The maximum angular position of the joint (ANGmax), torque required to achieve ANGmax (Tmax), and mean joint stiffness (K) were measured. Comparisons were made between able-bodied and paretic and able-bodied and nonparetic limbs.

RESULTS

Contrary to our expectations, between-group differences in ANGmax were observed only during hip extension in which ANGmax was greater bilaterally in people post-stroke compared to control subjects (P

CONCLUSION

This study demonstrates that community-ambulating stroke survivors with residual neuromuscular impairments do not have decreased lower extremity PROM caused by increased muscle stiffness or decreased muscle length. In fact, the population of stroke survivors examined here appears to have more hip extension PROM than age-matched able-bodied individuals. The clinical implications of these data are important and suggest that lower extremity PROM may not interfere with mobility in community-ambulating stroke survivors. Hence, physical therapists may choose to recommend activities other than stretching exercises for stroke survivors who are or will become independent community ambulators.

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Key Words

• cerebral vascular accident (cva)
• hemiparesis
• muscle
• range of motion (rom)
• spasticity

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MESH Headings

• Adult
• Aged
• Ankle Joint/physiopathology
• Case-Control Studies
• Cohort Studies
• Female
• Hip Joint/physiopathology
• Humans
• Lower Extremity/physiopathology
• Male
• Middle Aged
• Paresis/etiology
• Paresis/physiopathology
• Paresis/rehabilitation
• Range of Motion, Articular/physiology
• Stroke/complications
• Stroke/physiopathology
• Stroke Rehabilitation
• Walking/physiology

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Grants

• F32 HD044299 NICHD NIH HHS
• 1 F32 HD044299-01 NICHD NIH HHS

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Affiliation(s)

Sheila Schindler-Ivens Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
Davalyn Desimone
Sarah Grubich
Carolyn Kelley
Namita Sanghvi
David A Brown

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Motor unit discharge pattern and conduction velocity in patients with upper motor neuron syndrome

Motor unit properties were analyzed in patients with upper motor neuron syndrome (UMNS). Multi-channel surface electromyographic (EMG) signals were recorded for 300s from the biceps brachii muscle of seven male subacute patients (time from lesion, mean+/-SE, 4.9+/-1.0 months). In three patients, both arms were investigated, leading to 10 recorded muscles. Patients were analyzed in rest-like condition with motor units activated due to pathological muscle overactivity. For a total of 12 motor units, the complete discharge pattern was extracted from EMG decomposition. Interpulse interval variability was 7.8+/-0.9%. At minimum discharge rate (6.4+/-0.4 pulses per second, pps), conduction velocity was smaller than at maximum discharge rate (12.0+/-0.9pps) in all motor units (3.60+/-0.21m/s vs. 3.84+/-0.20m/s). Conduction velocity changed by 1.35+/-0.48% (different from zero, P<0.01) for each increase of 1pps in discharge rate. It was concluded that conduction velocity of low-threshold motor units in subacute patients with UMNS had similar values as reported in healthy subjects and was positively correlated to instantaneous discharge rate (velocity recovery function of muscle fibers).

The effect of poststroke impairments on brachialis muscle architecture as measured by ultrasound

OBJECTIVE

To evaluate the joint angle dependence of brachialis muscle architecture at rest and changes in brachialis muscle architecture during isometric voluntary contractions in people after stroke.

DESIGN

The pennation angle and fascicle length of the brachialis muscle were measured in the affected and unaffected sides of people after stroke at 9 different elbow angles ranging from 10 degrees to 90 degrees at the rest condition. Measurements were also carried out at a fixed joint angle of 90 degrees while the subjects were performing isometric muscle contractions at 5 incremental levels of maximal voluntary contraction (MVC) from 20% to 100% of MVC. The data obtained from the affected and unaffected sides of the subjects were compared.

SETTING

A research laboratory in a rehabilitation center.

PARTICIPANTS

Seven hemiplegic adults after stroke with passive range of motion in the elbow from 10 degrees to 90 degrees and Modified Ashworth Scale score larger than 1 were recruited.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Ultrasonography was used to measure brachialis muscle pennation angle and fascicle length at the rest condition and during isometric contractions.

RESULTS

The measured pennation angles and fascicle lengths were found to be joint-angle-dependent in both the affected and unaffected groups at the rest condition. Further comparisons found that the pennation angles of the affected brachialis muscle were significantly larger (P<.05) than the unaffected muscle in the most extended positions (<50 degrees ), whereas the affected fascicle lengths were significantly shorter (P<.05) than the unaffected muscle in most flexed positions (>20 degrees ). As the level of isometric voluntary contraction was increased incrementally from 20% to 100% of MVC, the results showed that pennation angle increased significantly (P<.05) while fascicle length decreased significantly (P<.01) in the unaffected muscle. However, the contraction level has a significant effect only on pennation angle (P<.05) but not on fascicle length in the affected side. In addition, the measured fascicle lengths in the unaffected group were significantly shorter than those in the affected group for isometric contractions above 40% MVC.

CONCLUSIONS

Our findings suggest that the architectural parameters of the brachialis muscle in people after stroke are elbow-joint-angle-dependent at the rest condition. In the affected side, pennation angle changed the most when the muscle was in an extension position and fascicle length changed the most in a flexed position when compared with the unaffected side. Immobilization and contracture might cause a shortening of the fascicle and an increase in pennation angle in the affected side. Smaller pennation angle and fascicle length changes in the affected side during isometric contraction might be due to weakness in the muscle after the onset of stroke.

Feedback-Controlled and Programmed Stretching of the Ankle Plantarflexors and Dorsiflexors in Stroke: Effects of a 4-Week Intervention Program

OBJECTIVE

To investigate the effect of repeated feedback-controlled and programmed "intelligent" stretching of the ankle plantar- and dorsiflexors to treat subjects with ankle spasticity and/or contracture in stroke.

DESIGN

Noncontrolled trial.

SETTING

Institutional research center.

PARTICIPANTS

Subjects with spasticity and/or contracture after stroke.

INTERVENTIONS

Stretching of the plantar- and dorsiflexors of the ankle 3 times a week for 45 minutes during a 4-week period by using a feedback-controlled and programmed stretching device.

MAIN OUTCOME MEASURES

Passive and active range of motion (ROM), muscle strength, joint stiffness, joint viscous damping, reflex excitability, comfortable walking speed, and subjective experiences of the subjects.

RESULTS

Significant improvements were found in the passive ROM, maximum voluntary contraction, ankle stiffness, and comfortable walking speed. The visual analog scales indicated very positive subjective evaluation in terms of the comfort of stretching and the effect on their involved ankle.

CONCLUSIONS

Repeated feedback-controlled or intelligent stretching had a positive influence on the joint properties of the ankle with spasticity and/or contracture after stroke. The stretching device may be an effective and safe alternative to manual passive motion treatment by a therapist and has potential to be used to repeatedly and regularly stretch the ankle of subjects with spasticity and/or contracture without daily involvement of clinicians or physical therapists.