Hemiparetic Subjects Research Articles

Task-Based Mirror Therapy Augmenting Motor Recovery in Poststroke Hemiparesis: A Randomized Controlled Trial

To establish the effect of the task-based mirror therapy (TBMT) on the upper limb recovery in stroke. A pilot, randomized, controlled, assessor-blinded trial was conducted in a rehabilitation institute. A convenience sample of 33 poststroke (mean duration, 12.5 months) hemiparetic subjects was randomized into 2 groups (experimental, 17; control, 16). The subjects were allocated to receive either TBMT or standard motor rehabilitation-40 sessions (5/week) for a period of 8 weeks. The TBMT group received movements using various goal-directed tasks and a mirror box. The movements were performed by the less-affected side superimposed on the affected side. The main outcome measures were Brunnstrom recovery stage (BRS) and Fugl-Meyer assessment (FMA)-FMA of upper extremity (FMA-UE), including upper arm (FMA-UA) and wrist-hand (FMA-WH). The TBMT group exhibited highly significant improvement on mean scores of FMA-WH (P < .001) and FMA-UE (P < .001) at postassessment in comparison to the control group. Furthermore, there was a 12% increase in the number of subjects at BRS stage 5 (out of synergy movement) in the experimental group as compared to a 0% rise at the same stage in the control group. This pilot trial confirmed the role of TBMT in improving the wrist-hand motor recovery in poststroke hemiparesis. MT using tasks may be used as an adjunct in stroke rehabilitation.

Velocidade de marcha e autoeficácia em quedas em indivíduos com hemiparesia após Acidente Vascular Encefálico

It is common that individuals after stroke show changes in the gait pattern, imbalance and more susceptibility to falls. This study aimed to assess the relationship between gait speed and self-efficacy for falls in hemiparetic subjects. The sample was composed of 23 individuals with hemiparesis due to stroke with a mean age of 60.6±11.26 years and 53.2±35.4 months of stroke evolution time. Participants were assessed for falls self-efficacy by the questionnaire Falls Efficacy Scale- International (FES-I). The normal and fast gait speed was calculated using the time spent to walk 10 meters. To verify the relationship between the FES-I and the gait speed were applied association and correlation tests. Among the participants, 39.1% used walking device and 30.4% reported falls in the previous year. The FES-I average was 30.3±8.4 points, the normal gait speed was 0.72±0.28m/s and fast gait speed was 1.00±0.40m/s. Participants were able to significantly modify the gait velocity (speed difference: 0.27±0.16m/s; paired t test: p<0.001). There was no correlation or association between the FES-I and the gait speed. A correlation was found between the FES-I and age (r=0.541; p=0.008); and association between use of walking device, both normal (p=0.048) and fast (p=0.037) gait speed. Although most individuals with hemiparesis from this study presented low self-efficacy for falls, yet they are able to modify the gait speed.

Electromyographic analysis of tibialis anterior and soleus muscles in hemiparetic patients on aquatic environment in comparison to land environment

Background: Acquired brain damage is a major cause of disability and have different clinical presentations, including motor, sensory, perceptual and cognitive impairments. Hemiparesis is the most common manifestation and causes changes in muscular strength and tonus, affecting voluntary motor control, which is related to limitations in functional activities, like daily life activities in orthostatism.Anklemuscles have a key role in stability and balance strategies in this posture. It is necessary to understand how muscles behave in different therapeutic environments. Purpose: The aim of this study was to verify muscle activation of tibialis anterior and soleus in hemiparetic patients and healthy subjects on aquatic environment in comparison to the muscle activation on land environment. Methods: This is an observational, cross-sectional study performed at a Brazilian rehabilitation centre. The sample was composed by twelve subjects – six patients with brain damage were included in the experimental group (EG), and six healthy subjects were included in the control group (CG). All subjects should: be between 18 and 60 years, without orthopaedic deformities, and be able to stand up with no support in aquatic environment. Patients should be within five years of the brain damage. EG were evaluated using the following assessments:Mini-Mental Test (MMT),BergBalance Scale (BBS), Functional IndependenceMeasure (FIM), muscular strength and muscular tone. EG and CGwere evaluated by an electromyographic (EMG) analysis of tibialis anterior and soleus muscles in both aquatic and land enviroments in different stand positions (orthostatism, squatting) in two levels of immersion in water (iliac crest and xiphoid process). The data were analyzed statistically using Mann-Whitney, Wilcoxon Tests; Spearman correlation. Due to small sample, significance level: p< 0.01. Results: Sample was composed by twelve subjects (mean age40± 12.4 years, 50%male).CGhas amean age40± 12.4 years, 50% male. EG has a mean age of 40.3± 12.9 years, 50% male; patients has hemiparesis caused by: 3: stroke, 2: cancer and 1: neuro-infection. Mean time after injury: 34.2± 18.1 months; 4 subjects with right hemiparesis and 2 with left hemiparesis. The sample was homogeneous in all parameters. Comparisons between groups were made of all data (intra-group and intergroup). EMG analysis showed statistical significance in EG, presenting greater activation of tibialis anterior and soleus in all activities in both levels of immersion, as well as in land environment (comparing to CG). Comparing land X water, a greater number of motor units were recruited in land. A inverse correlation was found between EMG and BBS in EG. Conclusion(s): Muscle activation of tibialis anterior and soleus is different on aquatic environment in comparison to muscle activation on land environment, and it is correlated with balance assessment. Implications:Our research findings assist physical therapists to understanding bettermuscle activation of hemiparetic patients on aquatic environment, contributing to the most appropriate intervention in aquatic physiotherapy.

Effect of motor training involving the less-affected side (MTLA) in post-stroke subjects: a pilot randomized controlled trial

Introduction:Poststroke, less-severe motor impairment occurs on the ipsilesional side of body. The objective of the present study was to evaluate the effectiveness of the motor training involving the less-affected side (MTLA) in stroke.Methods:This was a randomized, controlled, double-blinded pilot study conducted in the occupational therapy unit of a rehabilitation Institute. A convenience sample of 35 stroke subjects (mean poststroke duration, 28.76 weeks) was randomized into two groups (the experimental group: 17 and control group: 18). Thirty-two participants completed the entire study protocol. The experimental group and control group were provided MTLA and neurophysiological-based conventional therapy respectively. Both the groups received 24 treatment sessions (60 minutes each) over the period of two months. The Affected side was assessed using Brunnstrom recovery stage (BRS) and Fugl-Meyer assessment (FMA) whereas the less-affected side was evaluated by Minnesota manual dexterity test (MMDT), Purdue peg board test (PPBT) and Manual Muscle Testing (MMT).Results:Postintervention, the less-affected side of experimental group demonstrated significant improvement for MMDT (P = 0.003), PPBT (P = 0.01) and MMT (P < 0.001 to 0.043) in comparison to the control group. Further, as compared to the control group, the experimental group exhibited positive significant change for the measure of affected side [BRS (P < 0.001) and FMA (P < 0.001 to 0.03)] at post assessment.Conclusion:MTLA enhanced the muscle strength, dexterity and coordination of the less-affected side as well as the motor recovery of the affected side in poststroke hemiparetic subjects.

A influência das demandas atencionais no controle postural de hemiparéticos

Objective. To investigate the effects of dual task with cognitive de­mand on postural control of hemiparetic subjects post stroke. Meth­od. 18 subjects (52.28±13.8 years) with chronic hemiparesis, able to walk with or without gait assistance device. The Timed Up and Go test was used (TUG)- it was requested the individual to rise from a chair, walk three meters, return to the chair and sit down, and the Dynamic Gait Index (DGI) where individuals performed eight tasks involving gait in different sensorial contexts, with and without associ­ated cognitive demand, to assess the balance. Results. It was found that the cognitive demand influenced on the test results, the DGI showed a decrease in score (-3.05) and a time increase on the TUG (2.60) for holding both with a cognitive demand. But there was no difference in reducing the DGI score or increase the TUG time, in the dual task, compared to gender (p=0.860 and p=0.069), educational level (p=0.973 and p=0.571), type of stroke (p=0.408 and p=0.408), and affected hemisphere (p=0.798 and p=0.101). Conclusion. The realization of the dual task by inserting a cognitive demand influences on postural control of hemiparetic subjects post stroke.

Stretch-sensitive paresis and effort perception in hemiparesis.

In spastic paresis, stretch applied to the antagonist increases its inappropriate recruitment during agonist command (spastic co-contraction). It is unknown whether antagonist stretch: (1) also affects agonist recruitment; (2) alters effort perception. We quantified voluntary activation of ankle dorsiflexors, effort perception, and plantar flexor co-contraction during graded dorsiflexion efforts at two gastrocnemius lengths. Eighteen healthy (age 41 ± 13) and 18 hemiparetic (age 54 ± 12) subjects performed light, medium and maximal isometric dorsiflexion efforts with the knee flexed or extended. We determined dorsiflexor torque, Root Mean Square EMG and Agonist Recruitment/Co-contraction Indices (ARI/CCI) from the 500 ms peak voluntary agonist recruitment in a 5-s maximal isometric effort in tibialis anterior, soleus and medial gastrocnemius. Subjects retrospectively reported effort perception on a 10-point visual analog scale. During gastrocnemius stretch in hemiparetic subjects, we observed: (1) a 25 ± 7 % reduction of tibialis anterior voluntary activation (maximum reduction 98 %; knee extended vs knee flexed; p = 0.007, ANOVA); (2) an increase in dorsiflexion effort perception (p = 0.03, ANCOVA). Such changes did not occur in healthy subjects. Effort perception depended on tibialis anterior recruitment only (βARI(TA) = 0.61, p < 0.01) in healthy subjects (not on gastrocnemius medialis co-contraction) while it depended on both tibialis anterior agonist recruitment (βARI(TA) = 0.41, p < 0.001) and gastrocnemius medialis co-contraction (βCCI(MG) = 0.43, p < 0.001) in hemiparetic subjects. In hemiparesis, voluntary ability to recruit agonist motoneurones is impaired--sometimes abolished--by antagonist stretch, a phenomenon defined here as stretch-sensitive paresis. In addition, spastic co-contraction increases effort perception, an additional incentive to evaluate and treat this phenomenon.

Effects of Hand Vibration on Motor Output in Chronic Hemiparesis

Background.Muscle vibration has been shown to increase the corticospinal excitability assessed by transcranial magnetic stimulation (TMS) and to change voluntary force production in healthy subjects.Objectives.To evaluate the effect of vibration on corticospinal excitability using TMS and on maximal motor output using maximal voluntary contraction (MVC) in individuals with chronic hemiparesis.Methodology.Nineteen hemiparetic and 17 healthy control subjects participated in this study. Motor evoked potentials (MEPs) and MVC during lateral pinch grip were recorded at first dorsal interosseous muscle in a single session before, during, and after one-minute trials of 80 Hz vibration of the thenar eminence.Results.In hemiparetic subjects, vibration increased MEP amplitudes to a level comparable to that of control subjects and triggered a MEP response in 4 of 7 patients who did not have a MEP at rest. Also, vibration increased the maximal rate of force production (dF/dtmax⁡) in both control and hemiparetic subjects but it did not increase MVC.Conclusion.Motor response generated with a descending cortical drive in chronic hemiparetic subjects can be increased during vibration. Vibration could be used when additional input is needed to reveal motor responses and to increase rate of force generation.

Robot-assisted training of the kinesthetic sense: enhancing proprioception after stroke.

Proprioception has a crucial role in promoting or hindering motor learning. In particular, an intact position sense strongly correlates with the chances of recovery after stroke. A great majority of neurological patients present both motor dysfunctions and impairments in kinesthesia, but traditional robot and virtual reality training techniques focus either in recovering motor functions or in assessing proprioceptive deficits. An open challenge is to implement effective and reliable tests and training protocols for proprioception that go beyond the mere position sense evaluation and exploit the intrinsic bidirectionality of the kinesthetic sense, which refers to both sense of position and sense of movement. Modulated haptic interaction has a leading role in promoting sensorimotor integration, and it is a natural way to enhance volitional effort. Therefore, we designed a preliminary clinical study to test a new proprioception-based motor training technique for augmenting kinesthetic awareness via haptic feedback. The feedback was provided by a robotic manipulandum and the test involved seven chronic hemiparetic subjects over 3 weeks. The protocol included evaluation sessions that consisted of a psychometric estimate of the subject’s kinesthetic sensation, and training sessions, in which the subject executed planar reaching movements in the absence of vision and under a minimally assistive haptic guidance made by sequences of graded force pulses. The bidirectional haptic interaction between the subject and the robot was optimally adapted to each participant in order to achieve a uniform task difficulty over the workspace. All the subjects consistently improved in the perceptual scores as a consequence of training. Moreover, they could minimize the level of haptic guidance in time. Results suggest that the proposed method is effective in enhancing kinesthetic acuity, but the level of impairment may affect the ability of subjects to retain their improvement in time.

Comparison between the effects of task oriented program and balance training on postural stability in stroke patients

Background: Sensorimotor cortex is responsive to peripheral and central stimulation by mechanisms that are important for learning motor tasks. The purpose of this study was to investigate difference between the effect of task oriented program and balance exercises on postural stability in stroke patients.Subjects and procedures: Thirty stroke hemiparetic subjects were assigned into two equal groups (group I and II): group ( I ) received task oriented training program in addition to selected physical therapy program ( PNF technique, weight bearing exercises and gait training ) while group ( II ) received balance exercise in addition to selected physical therapy program ( PNF technique, weight bearing exercises and gait training ). Subjects were assessed using biodex stability system including postural stability test. Results: This study revealed that balance is significantly improved in both groups with the best results for group I. Conclusion: Task oriented training could be considered a valuable method for treating balance in stroke patients.

Dynamic time warping analysis in post-stroke rehabilitation

Abstract This paper presents the application of the Dynamic Time Warping (DTW) algorithm in the analysis of human functional movements in activities of daily living (ADLs). Dynamic Time Warping was originally developed for automatic speech recognition, though the method has been adopted by several fi elds of biomechanics. As a part of the post-stroke rehabilitation project COSMOSYS, the aim is to quantify the ADL performances of hemiparetic subjects, hence to be able to track their progress during physiotherapy. DOI: 10.17489/biohun/2014/2/06

Examination of Poststroke Alteration in Motor Unit Firing Behavior Using High-Density Surface EMG Decomposition.

Recent advances in high-density surface electromyogram (EMG) decomposition have made it a feasible task to discriminate single motor unit activity from surface EMG interference patterns, thus providing a noninvasive approach for examination of motor unit control properties. In the current study, we applied high-density surface EMG recording and decomposition techniques to assess motor unit firing behavior alterations poststroke. Surface EMG signals were collected using a 64-channel 2-D electrode array from the paretic and contralateral first dorsal interosseous (FDI) muscles of nine hemiparetic stroke subjects at different isometric discrete contraction levels between 2 to 10 N with a 2 N increment step. Motor unit firing rates were extracted through decomposition of the high-density surface EMG signals and compared between paretic and contralateral muscles. Across the nine tested subjects, paretic FDI muscles showed decreased motor unit firing rates compared with contralateral muscles at different contraction levels. Regression analysis indicated a linear relation between the mean motor unit firing rate and the muscle contraction level for both paretic and contralateral muscles (p < 0.001), with the former demonstrating a lower increment rate (0.32 pulses per second (pps)/N) compared with the latter (0.67 pps/N). The coefficient of variation (averaged over the contraction levels) of the motor unit firing rates for the paretic muscles (0.21 ± 0.012) was significantly higher than for the contralateral muscles (0.17 ± 0.014) (p < 0.05). This study provides direct evidence of motor unit firing behavior alterations poststroke using surface EMG, which can be an important factor contributing to hemiparetic muscle weakness.

The Relationship Between Pelvic Angles and The Ability of The Sit-to-stand Movement in Hemiparetic Subjects

To investigate the relationship between the anteversion and retroversion of pelvic angles and the ability of the sit-to-stand movement.

Stroke-induced synergistic phase shifting and its possible implications for recovery mechanisms.

Among other diminished motor capabilities, survivors of a stroke often exhibit pathological joint synergies. With respect to the upper limbs, these deficits diminish coordination in reaching, pointing, and daily task performance. Past research on pathological synergies suggests that the synergistic relationship between joints is different for flexion than in extension. One explanation for different flexion and extension synergies is that there exists a time difference between the joint being volitionally moved and the joint that moves in synergy. The goal of this research was to measure these synergistic time differences. The experiment included 11 hemiparetic subjects who performed rhythmic elbow motions at five different frequencies. A motion capture system was used to record the resulting shoulder synergies. Synergistic shoulder rotations were found to exhibit frequency-dependent phase lags (delays) and leads (advances) in the paretic arm. Furthermore, the synergistic leads and lags varied with frequency and were subject specific. We found that timing differences between joints in pathological movements are comparable to differences that were observed by other researchers for normal, able-bodied movement synergies. Moreover, the fact that pathological synergies were evident in rhythmic motion suggests that they are spinal in origin. A significant amount research exists relating to able-bodied spinal synergies. Thus, the supposition that pathological synergies are an expression of normal synergies would tie disabled movement into a larger body of work related to able-bodied synergies. The rehabilitation implications of this possible connection are discussed.

Interlimb neural coupling: Implications for poststroke hemiparesis

Interlimb coordination is essential to perform goal-directed daily tasks and purposeful locomotion. The coordination occurs due to spatiotemporal coupling of movements, which also comprises interactions in segmental kinematics, joint dynamics, and muscle activity. Neuroanatomical and neurophysiological linkages at the spinal and brain level are responsible for the coordination. The linkage is termed “neural coupling”. According to the task demand, the coupling may occur between two upper limbs or two lower limbs or all four limbs. Central pattern generators play a key role in interlimb coordination by regulating the rhythmic upper and lower limb movements. Neuroanatomically, multiple areas of both cerebral hemispheres via the corpus callosum interact and control the bimanual upper limb movements. There is an interhemispheric synchronization and disinhibition to control the coupled bimanual upper and lower limb movements. Movement of the upper limb also enhances neuromuscular recruitment of the lower limb. In stroke, bimanual motor impairments exist in the form of asymmetry and reduced coordination, which may be related to weakness of the ipsilateral body side lesser than the contralateral side. The aim of the present review was to understand the interlimb coordination and neural coupling and its implication in stroke rehabilitation. The review suggests incorporating the movements of bilateral upper and lower limbs either simultaneously or consecutively for hemiparetic subjects. Further, the conventional and contemporary rehabilitation methods need to be reconsidered while utilizing the coupling concept.

Forward propulsion asymmetry is indicative of changes in plantarflexor coordination during walking in individuals with post-stroke hemiparesis

BackgroundA common measure of rehabilitation effectiveness post-stroke is self-selected walking speed, yet individuals may achieve the same speed using different coordination strategies. Asymmetry in the propulsion generated by each leg can provide insight into paretic leg coordination due to its relatively strong correlation with hemiparetic severity. Subjects walking at the same speed can exhibit different propulsion asymmetries, with some subjects relying more on the paretic leg and others on the nonparetic leg. The goal of this study was to assess whether analyzing propulsion asymmetry can help distinguish between improved paretic leg coordination versus nonparetic leg compensation. MethodsThree-dimensional forward dynamics simulations were developed for two post-stroke hemiparetic subjects walking at identical speeds before/after rehabilitation with opposite changes in propulsion asymmetry. Changes in the individual muscle contributions to forward propulsion were examined. FindingsThe major source of increased forward propulsion in both subjects was from the ankle plantarflexors. How they were utilized differed and appears related to changes in propulsion asymmetry. Subject A increased propulsion generated from the paretic plantarflexors, while Subject B increased propulsion generated from the nonparetic plantarflexors. Each subject's strategy to increase speed also included differences in other muscle groups (e.g., hamstrings) that did not appear to be related to propulsion asymmetry. InterpretationThe results of this study highlight how speed cannot be used to elucidate underlying muscle coordination changes following rehabilitation. In contrast, propulsion asymmetry appears to provide insight into changes in plantarflexor output affecting propulsion generation and may be useful in monitoring rehabilitation outcomes.

Effect of Body Mass Index on Hemiparetic Gait

To evaluate the relationship between body mass index (BMI) and spatiotemporal, kinematic, and kinetic gait parameters in chronic hemiparetic stroke survivors. Secondary analysis of data collected in a randomized controlled trial comparing two 12-week ambulation training treatments. Academic medical center. Chronic hemiparetic stroke survivors (N = 108, >3 months poststroke) Linear regression analyses were performed of BMI, and selected pretreatment gait parameters were recorded using quantitative gait analysis. Spatiotemporal, kinematic, and kinetic gait parameters. A series of linear regression models that controlled for age, gender, stroke type (ischemic versus hemorrhagic), interval poststroke, level of motor impairment (Fugl-Meyer score), and walking speed found BMI to be positively associated with step width (m) (β = 0.364, P < .001), positively associated with peak hip abduction angle of the nonparetic limb during stance (deg) (β = 0.177, P = .040), negatively associated with ankle dorsiflexion angle at initial contact of the paretic limb (deg) (β = -0.222, P = .023), and negatively associated with peak ankle power at push-off (W/kg) of the paretic limb (W/kg)(β = -0.142, P = .026). When walking at a similar speed, chronic hemiparetic stroke subjects with a higher BMI demonstrated greater step width, greater hip hiking of the paretic lower limb, less paretic limb dorsiflexion at initial contact, and less paretic ankle power at push-off as compared to stroke subjects with a lower BMI and similar level of motor impairment. Further studies are necessary to determine the clinical relevance of these findings with respect to rehabilitation strategies for gait dysfunction in hemiparetic patients with higher BMIs.

Activation deficit correlates with weakness in chronic stroke: Evidence from evoked and voluntary EMG recordings

ObjectiveTo use evoked (M-wave) and voluntary (during maximal voluntary contraction (MVC)) EMG recordings to estimate the voluntary activation level in chronic stroke. MethodsNine chronic hemiparetic stroke subjects participated in the experiment. M-wave (EMGM-wave) and MVC (EMGMVC) EMG values of the biceps brachii muscles were recorded. ResultsPeak torque was significantly smaller on the impaired than non-impaired side. EMGM-wave was also significantly smaller on the impaired than non-impaired side. However, the normalized EMGM-wave/TorqueMVC ratio was not significantly different between two sides. In contrast, both absolute EMGMVC and normalized EMGMVC/TorqueMVC were smaller on the impaired than non-impaired side. The voluntary activation level, EMGMVC/M-wave, was also smaller on the impaired than non-impaired side. The voluntary activation level on the impaired side was highly correlated with weakness (R=0.72), but very low (R=0.32) on the non-impaired side. ConclusionCollectively, our findings suggest that both peripheral and central factors contribute to post-stroke weakness, but activation deficit correlates most closely with weakness as estimated from maximum voluntary torque generation. SignificanceThese findings serve to highlight the potential benefit from high-intensity exercises to enhance central activation for facilitation of motor recovery.

The impact of foot position on sit-to-stand stability and lower limb loading in hemiplegic stroke patients

Objective To explore the effects of different foot positions on lower limb loading and the sit- to-stand stability of hemiplegic stroke patients. Methods Thirty-six hemiplegic stroke patients were recruited as the experimental group and 36 healthy elderly as the control group. Both groups of subjects completed sit-to-stand movements with 3 different foot positions： （ 1 ） both feet （BF） placed at 10° of ankle dorsiflexion; （2） the paretic foot placed posterior （PFP） for hemiparetic subjects or the undominant foot placed posterior （UDFP） for healthy subjects; （3） the non-paretic foot placed posterior （NPFP） for hemiparetic subjects or the dominant foot placed posterior （DFP） for healthy subjects. The time required to rise from sitting, the average load difference （ALD） be- tween the left and right feet and sway of the center of gravity in the mediolateral direction （COGX） were measured. Results Comparing BF with PFP positioning, the time to rise was not significantly different but the loads on the two legs, the ALD and the COGX in were all significantly different. Comparing NPFP with PFP positioning, all the indexes were significantly different, and the time to rise was significantly different from the BF positioning. For the control group, all the indexes significantly different in the BP and PFP positions, and the time to rise was signifi- cantly different from that required with the UDFP placement. In all 3 foot positions, all of the experimental group＇ s indices differed significantly from those of the control group. In both groups there was a strong positive correlation between the average ALD and COGX values in all three foot positions. Conclusions Foot placement influences lower limb loading and stability in rising from sitting for hemiplegic stroke survivors. The greater the symmetry of lower limb loading, the better the postural stability. Key words: Stroke ; Hemiplegia; Sit-to-stand ; Posture ; Lower limb loading

The influence of solid ankle-foot-orthoses on forward propulsion and dynamic balance in healthy adults during walking

BackgroundIn post-stroke hemiparetic subjects, solid polypropylene ankle-foot-orthoses are commonly prescribed to assist in foot clearance during swing while bracing the ankle during stance. Mobility demands, such as changing walking speed and direction, are accomplished by accelerating or decelerating the body and maintaining dynamic balance. Previous studies have shown that the ankle plantarflexors are primary contributors to these essential biomechanical functions. Thus, with ankle-foot-orthoses limiting ankle motion and plantarflexor output during stance, execution of these walking subtasks may be compromised. This study examined the influence of a solid polypropylene ankle-foot-orthosis on forward propulsion and dynamic balance in healthy adults. MethodsKinematic and kinetic data were recorded from 10 healthy adults walking with and without a unilateral ankle-foot-orthosis at steady-state slow (0.6m/s) and moderate (1.2m/s) speeds, and during accelerated (0–1.8m/s at 0.06m/s2) and decelerated (1.8–0m/s at −0.06m/s2) walking. Propulsion was quantified by propulsive and braking impulses (i.e., time integral of the anterior–posterior ground reaction force) while dynamic balance was quantified by the peak-to-peak range of whole-body angular momentum. FindingsThe propulsive impulses decreased in the leg with ankle-foot-orthosis compared to the contralateral leg and no ankle-foot-orthosis condition. Further, the ankle-foot-orthosis resulted in a greater range of angular momentum in both the frontal and sagittal planes, which were correlated with the reduced peak hip abduction and reduced ankle plantarflexor moments, respectively. InterpretationSolid ankle-foot-orthoses limit the successful execution of important mobility subtasks in healthy adults and that the prescription of ankle-foot-orthosis should be carefully considered.

Differences in Plantar Flexor Fascicle Length and Pennation Angle between Healthy and Poststroke Individuals and Implications for Poststroke Plantar Flexor Force Contributions.

Poststroke plantar flexor muscle weakness has been attributed to muscle atrophy and impaired activation, which cannot collectively explain the limitations in force-generating capability of the entire muscle group. It is of interest whether changes in poststroke plantar flexor muscle fascicle length and pennation angle influence the individual force-generating capability and whether plantar flexor weakness is due to uniform changes in individual muscle force contributions. Fascicle lengths and pennation angles for the soleus, medial, and lateral gastrocnemius were measured using ultrasound and compared between ten hemiparetic poststroke subjects and ten healthy controls. Physiological cross-sectional areas and force contributions to poststroke plantar flexor torque were estimated for each muscle. No statistical differences were observed for any muscle fascicle lengths or for the lateral gastrocnemius and soleus pennation angles between paretic, nonparetic, and healthy limbs. There was a significant decrease (P < 0.05) in the paretic medial gastrocnemius pennation angle compared to both nonparetic and healthy limbs. Physiological cross-sectional areas and force contributions were smaller on the paretic side. Additionally, bilateral muscle contributions to plantar flexor torque remained the same. While the architecture of each individual plantar flexor muscle is affected differently after stroke, the relative contribution of each muscle remains the same.