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1.  Muscle Strength and Weight-Bearing Symmetry Relate to Sit-to-Stand Performance in Individuals with Stroke 
Gait & posture  2005;22(2):126-131.
This study investigated the relationship of lower extremity joint torques and weight-bearing symmetry to sit-to-stand (STS) performance in individuals with chronic stroke. A motion analysis system and two force plates measured STS duration and weight-bearing symmetry (determined by ground reaction forces) during three self-paced and three fast-paced conditions. An isokinetic dynamometer measured maximum concentric joint torques of the paretic and nonparetic ankle, knee, and hip, which were normalized by body mass. Pearson correlations indicated that (a) paretic ankle dorsiflexion and knee extension torques related to the duration of the self-paced STS condition (r = −0.450, −0.716, respectively), (b) paretic ankle dorsiflexion, plantar flexion, and knee extension torques related to the duration of the fast-paced STS condition (r = −0.466, −0.616, −0.736, respectively), and (c) greater weight-bearing symmetry related to faster STS performance for both self-paced and fast-paced STS conditions (r = −0.565, −0.564, respectively) (p < 0.05). This evidence suggests that paretic muscle strength and the ability to load the paretic limb are important factors underlying the ability to rise from a chair in individuals with chronic stroke.
PMCID: PMC3167866  PMID: 16139747 CAMSID: cams1870
Stroke; Sit-to-stand; Torque; Weight-bearing
2.  The influence of an ankle foot orthosis on the percentage of weight loading during standing tasks in stroke patients 
Journal of Physical Therapy Science  2015;27(9):2887-2890.
[Purpose] The aim of this study was to investigate the effects of an ankle foot orthosis on weight-bearing abilities of stroke patients by comparing weight loading during performance of tasks in various standing positions on the affected side. [Subjects and Methods] This study was performed with 16 stroke patients. To measure the weight loading value and percentage of weight loading in affected lower extremities, 5 standing tasks were performed with and without an ankle foot orthosis in random order. [Results] In the rising from a chair, maintaining a standing position, and forward weight shifting tasks, the affected lower extremities showed a significantly higher percentage of weight loading with an ankle foot orthosis. In the tasks requiring weight shifting to one leg, weight shifting to the lateral side showed the best weight-bearing ability with or without an ankle foot orthosis, followed by the forward and backward weight shifting, respectively. There were statistically significant correlations in all 5 tasks with or without an ankle foot orthosis. [Conclusion] An ankle foot orthosis improves the weight-bearing ability, especially when shifting weight forward, resulting in increased weight-bearing ability in activities of daily living tasks such as quiet standing and rising from a chair. The 5 tasks in this study would be a fine assessment tool under clinical conditions to investigate the postural stability of the affected side with or without application of an ankle foot orthosis.
PMCID: PMC4616119  PMID: 26504318
Ankle foot orthosis; Stroke; Weight-bearing ability
3.  Lower Extremity Passive Range of Motion in Community-Ambulating Stroke Survivors 
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.
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.
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 ≤ 0.05; stroke = 13 degrees, able-bodied = −1 degree). Tmax, but not K, was also significantly higher during passive hip extension in paretic and nonparetic limbs compared to control limbs (P ≤ 0.05; stroke = 40 Nm, able-bodied = 29 Nm). Compared to the control group, Tmax was increased during hip flexion in the paretic and nonparetic limbs of post-stroke subjects (P ≤ 0.05, stroke = 25 Nm, able-bodied = 18 Nm). K in the nonparetic leg was also increased during hip flexion (P ≤ 0.05, nonparetic = 0.52 Nm/degree, able-bodied = 0.37 Nm/degree.)
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.
PMCID: PMC3963266  PMID: 18463552
cerebral vascular accident (CVA); hemiparesis; muscle; range of motion (ROM); spasticity
4.  Muscle torque preservation and physical activity in individuals with stroke 
A greater percent loss of concentric versus eccentric muscle torque (i.e., relative eccentric muscle torque preservation) has been reported in the paretic limb of individuals with stroke and has been attributed to hypertonia and/or co-contractions. Stroke provides a unique condition for examining mechanisms underlying eccentric muscle preservation because both limbs experience similar amounts of general physical activity, but the paretic side is impaired directly by the brain lesion.
The purpose of this study was to determine 1) whether eccentric preservation also exists in the nonparetic limb and 2) the relationship of eccentric or concentric torque preservation with physical activity in stroke. We hypothesized that the nonparetic muscles would demonstrate eccentric muscle preservation, which would suggest that non-neural mechanisms may also contribute to its relative preservation.
Eighteen stroke and 18 healthy control subjects (age and sex matched) completed a physical activity questionnaire. Maximum voluntary concentric and eccentric joint torques of the ankle, knee and hip flexors and extensors were measured using an isokinetic dynamometer at 30°/s for the paretic and nonparetic muscles. Relative concentric and eccentric peak torque preservation were expressed as a percentage of control subject torque.
Relative eccentric torque was higher (more preserved) than relative concentric torque for paretic, as well as nonparetic muscles. Physical activity correlated with paretic (r=0.640, p=0.001) and nonparetic concentric torque preservation (r=0.508, p=0.009), but not with eccentric torque preservation for either leg.
The relative preservation of eccentric torque in the nonparetic muscles suggest a role of non-neural mechanisms and could also explain the preservation observed in other chronic health conditions. Loss of concentric, but not eccentric muscle torque was related to physical inactivity in stroke.
PMCID: PMC3114014  PMID: 19516167 CAMSID: cams1776
strength; rehabilitation; force; CVA
5.  Clinical usefulness and validity of robotic measures of reaching movement in hemiparetic stroke patients 
Various robotic technologies have been developed recently for objective and quantitative assessment of movement. Among them, robotic measures derived from a reaching task in the KINARM Exoskeleton device are characterized by their potential to reveal underlying motor control in reaching movements. The aim of this study was to examine the clinical usefulness and validity of these robot-derived measures in hemiparetic stroke patients.
Fifty-six participants with a hemiparetic arm due to chronic stroke were enrolled. The robotic assessment was performed using the Visually Guided Reaching (VGR) task in the KINARM Exoskeleton, which allows free arm movements in the horizontal plane. Twelve parameters were derived based on motor control theory. The following clinical assessments were also administered: the proximal upper limb section in the Fugl-Meyer Assessment (FMA-UE(A)), the proximal upper limb part in the Stroke Impairment Assessment Set (SIAS-KM), the Modified Ashworth Scale for the affected elbow flexor muscles (MAS elbow), and seven proximal upper limb tasks in the Wolf Motor Function Test (WMFT). To explore which robotic measures represent deficits of motor control in the affected arm, the VGR parameters in the paretic arm were compared with those in the non-paretic arm using the Wilcoxon signed rank test. Then, to explore which VGR parameters were related to overall motor control regardless of the paresis, correlations between the paretic and non-paretic arms were examined. Finally, to investigate the relationships between the robotic measures and the clinical scales, correlations between the VGR parameters and clinical scales were investigated. Spearman’s rank correlation coefficients were used for all correlational analyses.
Eleven VGR parameters on the paretic side were significantly different from those on the non-paretic side with large effect sizes (|effect size| = 0.76–0.87). Ten VGR parameters correlated significantly with FMA-UE(A) (|r| = 0.32–0.60). Eight VGR parameters also showed significant correlations with SIAS-KM (|r| = 0.42–0.49), MAS elbow (|r| = 0.44–0.48), and the Functional Ability Scale of the WMFT (|r| = 0.52–0.64).
The robot-derived measures could successfully differentiate between the paretic arm and the non-paretic arm and were valid in comparison to the well-established clinical scales.
PMCID: PMC4533801  PMID: 26265327
6.  Effect of Body Mass Index on Hemiparetic Gait 
To evaluate the relationship between body mass index 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 post-stroke)
Linear regression analyses were performed of body mass index (BMI) and selected pretreatment gait parameters recorded using quantitative gait analysis
Main Outcome Measures
Spatiotemporal, kinematic, and kinetic gait parameters
A series of linear regression models which controlled for age, gender, stroke type (ischemic versus hemorrhagic), interval post-stroke, level of motor impairment (Fugl-Meyer score), and walking speed found BMI to be positively associated with step width (m) (β=.364, p<.001), positively associated with peak hip abduction angle of the nonparetic limb during stance (deg) (β=.177, p=.040), negatively associated with ankle dorsiflexion angle at initial contact of the paretic limb (deg)(β=-.222, p=.023), and negatively associated with peak ankle power at push-off (W/kg) of the paretic limb (W/kg)(β=-.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.
PMCID: PMC4185303  PMID: 24713181
Body Mass Index; Stroke; Rehabilitation
7.  Biofeedback rehabilitation of posture and weight-bearing distribution in stroke: a center of foot pressure analysis 
Functional Neurology  2014;29(2):127-134.
Weight bearing on the paretic lower extremity and transfer of weight from one lower extremity to the other are important goals of stroke rehabilitation. Improvements in these limb loading and weight transfer abilities have been shown to relate to improved performance of many functional activities. Unfortunately, valid and practical clinical measures of paretic lower extremity loading and weight transfer have not been identified.
The purpose of this study was to quantitatively assess, through center of foot pressure (CoP) analysis of quiet upright stance control, recovery of paretic limb loading as a measure of weight transfer in early stroke subjects, testing the effectiveness of a targeted rehabilitation intervention based on audio-visual biofeedback.
Thirty-seven adults with lower extremity motor impairment following unilateral, non-cerebellar stroke, were tested twice, at an interval of at least one month post stroke and following rehabilitation intervention aimed at correcting their asymmetrical weight bearing. The intervention was performed with (Study Group, SG) or without (Control Group, CG) a postural audio-visual biofeedback approach. Indices of postural stability and of balance control asymmetry were estimated by acquiring the movements of the CoP during quiet upright stance condition with or without visual input (eyes open, EO and eyes closed, EC). Clinical scales were also administered. Both the CG and the SG subjects showed improved control in upright stance posture as documented by significant improvements in the scale scores and indices of stability during both the EO and the EC condition. Only the SG showed a significantly reduced CoP index of asymmetry.
The CoP index of asymmetry, correlating with clinical motor scales, is a valid measure of paretic limb loading during stroke recovery. Postural audio-visual biofeedback represented the more effective approach for reducing weight loading asymmetry of the lower limbs in stroke.
PMCID: PMC4198161  PMID: 25306123
asymmetry index; biofeedback; neurorehabilitation; posturography; stroke; weight bearing
8.  The characteristics of multi-directional step distance and the association between stepping laterality and walking ability of patients with stroke 
[Purpose] The purpose of this study was to determine the effect of stepping limb and step direction on step distance and the association of step distance and stepping laterality in step difference with walking ability and motor dysfunction. [Subjects and Methods] The subjects were thirty-nine patients with chronic hemiparesis as a result of stroke, who performed the MSL (Maximum Step Length) test along with tests of motor impairment, gait speed and Functional Ambulation Category. The MSL test is a clinical test of stepping distance in which participants step to the front, side, and back. The subjects were classified into three groups according to the stepping laterality in front step distance. [Results] Step distance did not differ across stepping limbs but did differ across step directions. Front step distance was significantly longer than side and back step distance. Participants with forward paretic step length shorter than forward non-paretic step length had significantly higher walking ability than participants with symmetric forward step length or forward paretic step length longer than forward non-paretic step length [Conclusion] Patients with stroke have characteristic step distances in each direction. Adequate weight shift toward the paretic limb when stepping with the non-paretic limb is associated with walking ability.
PMCID: PMC4395740  PMID: 25931756
Maximum step length; Stepping laterality; Stroke
9.  Interference Between Cognition, Double-Limb Support, and Swing During Gait in Community-Dwelling Individuals Poststroke 
Dual tasking can interfere with activity after stroke.
The authors examined the interactions between 3 different cognitive tasks and the swing and double-limb support (DLS) components of the gait cycle in community-dwelling individuals poststroke.
Acquisition of cognitive and gait data were synchronized to study the cognitive–motor interference effects during the different phases of the gait cycle. Participants performed 3 different cognitive tasks in isolation and in combination with walking as well as a single walking task. Tasks were performed continuously for 3 minutes, generating 131 ± 39 gait cycles per person for analysis for each walking trial. Data were analyzed for 8 participants 7.6 ± 4.2 months poststroke.
A significant increase was found in the proportion of the gait cycle spent in DLS in dual-task walking because of an increased duration of the DLS phase associated with paretic weight acceptance. There was a significant dual-task effect on nonparetic swing duration: participants reduced the amount of time in paretic single-limb stance in the 3 dual-task conditions. Temporal asymmetry of gait did not increase significantly under dual-task conditions. Reaction times were not affected by whether the stimuli were present during the swing or DLS phase of the gait cycle.
The findings from this pilot study provide evidence that cognitive–motor interference during gait may be influenced by the phase of the gait cycle, especially DLS involving paretic weight acceptance, which may affect community ambulators with hemiparetic stroke.
PMCID: PMC2923473  PMID: 20424190
dual task; gait; stroke
10.  Relationships Between Muscle Activity and Anteroposterior Ground Reaction Forces in Hemiparetic Walking 
To determine relationships between muscle activity and propulsive impulse in hemiparetic walking.
Gait analysis laboratory.
Forty-nine poststroke patients with chronic hemiparesis, stratified into hemiparetic severity subgroups based on Brunnstrom stages of motor recovery, walking at their self-selected speed.
Not applicable.
Main Outcome Measures
Percent of muscle activity in the paretic and nonparetic legs and net anteroposterior (AP) ground reaction force impulse (ie, the time integral of the AP ground reaction force) within 4 regions of the stance phase (first double support, first and second halves of single support, and second double support).
Medial gastrocnemius and soleus muscle activity correlated positively with paretic propulsion in the second half of single support and double support across all subjects and subjects grouped by hemiparetic severity. Tibialis anterior correlated negatively with paretic propulsion during preswing across all subjects and for subjects with moderate and severe hemiparesis. Rectus femoris activity also correlated negatively with preswing propulsion for the severe group. Uniarticular knee extensor activity correlated only with increased paretic braking in the first double-support phase for the severe hemiparesis group. Nonparetic leg muscle activity correlated with propulsive impulses across all subjects, but not within the severe group exclusively.
Paretic propulsion is strongly associated with increased plantarflexor activity and also negatively associated with increased leg flexor activity, especially in the severe hemiparesis group. These results suggest that exaggerated flexor muscle activity may counteract the effects of the plantarflexors by offloading the leg and interfering with the limb’s ability to generate appropriate AP ground reaction forces. There is also evidence for specific relationships between paretic braking and nonparetic propulsive forces and changes in timing of muscle activation.
PMCID: PMC2367107  PMID: 17826457
Electromyography; Hemiparesis; Rehabilitation; Walking
11.  Kinetic measurements of hand motor impairments after mild to moderate stroke using grip control tasks 
The aim of this study is to investigate quantitative outcome measurements of hand motor performance for subjects after mild to moderate stroke using grip control tasks and characterize abnormal flexion synergy of upper extremities after stroke.
A customized dynamometer with force sensors was used to measure grip force and calculate rotation torque during the sub-maximal grip control tasks. The paretic and nonpartic sides of eleven subjects after stroke and the dominant sides of ten healthy persons were tested. Their maximal voluntary grip force was measured and used to set sub-maximal grip control tasks at three different target force levels. Force control ability was characterized by the maximal grip force, mean force percentage, coefficient of variation (CV), target deviation ratio (TDR), and rotation torque ratio (RTR). The motor impairments of subjects after stroke were also evaluated using the Fugl-Meyer assessment for upper extremity (FMA-UE) and Wolf Motor Function Test (WMFT).
Maximal grip force of the paretic side was significantly reduced as compared to the nonparetic side and the healthy group, while the difference of maximal grip force between the nonparetic side and the healthy group was not significant. TDR and RTR increased for all three groups with increasing target force level. There were significant differences of CV, TDR and RTR between the paretic side and the healthy group at all the force levels. CV, TDR and RTR showed significant negative correlations with FMA-UE and WMFT at 50% of maximum grip force.
This study designed a customized dynamometer together with an innovative measurement, RTR, to investigate the hand motor performance of subjects after mild to moderate stroke during force control tasks. And stroke-induced abnormal flexion synergy of wrist and finger muscles could be characterized by RTR. This study also identified a set of kinetic parameters which can be applied to quantitatively assess the hand motor function of subjects after mild to moderate stroke.
PMCID: PMC4038706  PMID: 24886085
Upper extremity; Movement disorders; Stroke; Rehabilitation
12.  Direction-Dependent Phasing of Locomotor Muscle Activity Is Altered Post-Stroke 
Journal of neurophysiology  2004;92(4):2207-2216.
A major contributor to impaired locomotion post-stroke is abnormal phasing of muscle activity. While inappropriate paretic muscle phasing adapts to changing body orientation, load, and speed, it remains unclear whether paretic muscle phasing adapts to reversal of locomotor direction. We examined muscle phasing in backward pedaling, a task that requires shifts in biarticular but not uniarticular muscle phasing relative to forward pedaling. We hypothesized that if paretic and neurologically intact muscle phasing adapt similarly, then paretic biarticular but not paretic uniarticular muscles would shift phasing in backward pedaling. Paretic and neurologically intact individuals pedaled forward and backward while recording electromyograms (EMGs) from vastus medialis (VM), soleus (SOL), rectus femoris (RF), semimembranosus (SM), and biceps femoris (BF). Changes in muscle phasing were assessed by comparing the probability of muscle activity in forward and backward pedaling throughout 18 pedaling cycles. Paretic uniarticular muscles (VM and SOL) showed phase-advanced activity in backward versus forward pedaling, whereas the corresponding neurologically intact muscles showed little to no phasing change. Paretic biarticular muscles were less likely than neurologically intact biarticular muscles to display phasing changes in backward pedaling. Paretic RF displayed no phase change during backward pedaling, and paretic BF displayed no consistent adaptation to backward pedaling. Paretic SM was the only muscle to display backward/forward phase changes that were similar to the neurologically intact group. We conclude that paretic uniarticular muscles are more susceptible and paretic biarticular muscles are less susceptible to direction-dependent phase shifts, consistent with altered sensory integration and impaired cortical control of locomotion.
PMCID: PMC3912995  PMID: 15175363
13.  Motor System Plasticity in Stroke Models: Intrinsically Use-dependent, Unreliably Useful 
Stroke; a journal of cerebral circulation  2013;44(6 0 1):S104-S106.
Background and Purpose
The natural response to disability in one limb is to learn new ways of using the other limb. This compensatory behavioral strategy after stroke has long been thought to contribute to persistent dysfunction in the paretic limb by encouraging its disuse. Our recent findings suggest that it goes beyond the encouragement of disuse to disrupt neural substrates of paretic limb functional improvements.
We overview recent findings from rodent models of chronic upper extremity impairments in which precise control and manipulation of forelimb experiences were used to understand bilateral and interhemispheric contributions to motor functional outcome.
Skill learning with the less-affected (nonparetic) forelimb promotes neural plasticity in the contralesional motor cortex that subserves its function. At the same time, it exacerbates dysfunction and limits the efficacy of rehabilitative training in the paretic limb. The maladaptive effects of skill learning with the nonparetic forelimb are dependent on callosal connections and contralesional motor cortex, and linked with reduced neural activation of peri-infarct motor cortex during rehabilitative training.
These findings suggest that learning to rely on the nonparetic body side has the capacity to disrupt functionality in a region of the injured hemisphere that contributes to outcome of the paretic limb. Whether this effect generalizes across injury loci and functional modalities remains to be tested.
PMCID: PMC3727618  PMID: 23709698
learned nonuse; motor cortex; manual skill; motor rehabilitative training; experience-expectant plasticity
14.  Changes in Cerebellar Activation After Onabotulinumtoxin A Injections for Spasticity After Chronic Stroke: A Pilot Functional Magnetic Resonance Imaging Study 
To investigate the effect of reducing spasticity via onabotulinumtoxin A (Obtx-A) injection on cerebellar activation after chronic stroke during unilateral gripping.
Pre-post, case series.
Outpatient spasticity clinic.
Individuals with chronic spasticity (N = 4).
Upper-limb Obtx-A injection.
Main Outcome Measures
Functional magnetic resonance imaging (fMRI) was used to measure changes in cerebellar activation before and after upper-limb Obtx-A injection. During fMRI testing, participants performed the same motor task before and after injection, which was 15% and 30% of maximum voluntary isometric gripping measured before Obtx-A injection.
After Obtx-A injection, cerebellar activation increased bilaterally during gripping with the paretic hand and during rest. During both pre- and postinjection scans, the paretic hand showed larger cerebellar activation during gripping compared with the nonparetic hand. Cerebellar activation during gripping with the nonparetic hand did not change significantly after Obtx-A injection.
Reducing spasticity via Obtx-A injection may increase cerebellar activation both during gripping tasks with the paretic hand and during rest. To our knowledge, this is the first study that examines changes in cerebellar activation after spasticity treatment with Obtx-A.
PMCID: PMC4628596  PMID: 26239302
Botulinum toxins; type A; Cerebellum; Magnetic resonance imaging; Muscle spasticity; Rehabilitation; Stroke
15.  Stepping before standing: hip muscle function in stepping and standing balance after stroke 
OBJECTIVE—To compare the pattern of pelvic girdle muscle activation in normal subjects and hemiparetic patients while stepping and maintaining standing balance.
DESIGN—Group comparison.
METHOD—Seventeen patients who had regained the ability to walk after a single hemiparetic stroke were studied together with 16 normal controls. Median interval between stroke and testing was 17 months. Amplitude and onset latency of surface EMG activity in hip abductors and adductors were recorded in response to sideways pushes in either direction while standing. Similar recordings were made in the same subjects during gait initiation and a single stride.
RESULTS—In the standing balance task, normal subjects resisted a sideways push to the left with the left gluteus medius (74 ms) and with the right adductor (111 ms), and vice versa. In hemiparetic patients, the amplitude of activity was reduced in the hemiparetic muscles, the onset latencies of which were delayed (gluteus medius 96 ms, adductor 144 ms). Contralateral, non-paretic, adductor activity was increased after a push towards the hemiparetic side of patients with stroke and the latency was normal (110 ms). During self initiated sideways weight shifts at gait initiation, hemiplegic muscle activation was impaired. By contrast, the pattern and peak amplitude of hip muscle activation in stepping was normal in both hemiparetic and non-hemiparetic muscles of the subjects with stroke.
CONCLUSIONS—In ambulant patients with stroke, a normal pattern of activation of hemiparetic muscles is seen in stepping whereas the response of these muscles to a perturbation while standing remains grossly impaired and is compensated by increased activity of the contralateral muscles. This suggests that hemiparetic patients should be able to step before regaining standing balance.

PMCID: PMC1736885  PMID: 10727481
16.  Sensory electrical stimulation improves foot placement during targeted stepping post-stroke 
Experimental brain research  2014;232(4):1137-1143.
Proper foot placement is vital for maintaining balance during walking, requiring the integration of multiple sensory signals with motor commands. Disruption of brain structures post-stroke likely alters the processing of sensory information by motor centers, interfering with precision control of foot placement and walking function for stroke survivors. In this study, we examined whether somatosensory stimulation, which improves functional movements of the paretic hand, could be used to improve foot placement of the paretic limb. Foot placement was evaluated before, during, and after application of somatosensory electrical stimulation to the paretic foot during a targeted stepping task. Starting from standing, twelve chronic stroke participants initiated movement with the non-paretic limb and stepped to one of five target locations projected onto the floor with distances normalized to the paretic stride length. Targeting error and lower extremity kinematics were used to assess changes in foot placement and limb control due to somatosensory stimulation. Significant reductions in placement error in the medial–lateral direction (p = 0.008) were observed during the stimulation and post-stimulation blocks. Seven participants, presenting with a hip circumduction walking pattern, had reductions (p = 0.008) in the magnitude and duration of hip abduction during swing with somatosensory stimulation. Reductions in circumduction correlated with both functional and clinical measures, with larger improvements observed in participants with greater impairment. The results of this study suggest that somatosensory stimulation of the paretic foot applied during movement can improve the precision control of foot placement.
PMCID: PMC4448948  PMID: 24449007
Stroke; Stepping; Electrical stimulation; Foot; Hip circumduction; Balance; Motor control
17.  Impaired H-Reflex Gain during Postural Loaded Locomotion in Individuals Post-Stroke 
PLoS ONE  2015;10(12):e0144007.
Successful execution of upright locomotion requires coordinated interaction between controllers for locomotion and posture. Our earlier research supported this model in the non-impaired and found impaired interaction in the post-stroke nervous system during locomotion. In this study, we sought to examine the role of the Ia afferent spinal loop, via the H-reflex response, under postural influence during a locomotor task. We tested the hypothesis that the ability to increase stretch reflex gain in response to postural loads during locomotion would be reduced post-stroke.
Fifteen individuals with chronic post-stroke hemiparesis and 13 non-impaired controls pedaled on a motorized cycle ergometer with specialized backboard support system under (1) seated supported, and (2) non-seated postural-loaded conditions, generating matched pedal force outputs of two levels. H-reflexes were elicited at 90°crank angle.
We observed increased H-reflex gain with postural influence in non-impaired individuals, but a lack of increase in individuals post-stroke. Furthermore, we observed decreased H-reflex gain at higher postural loads in the stroke-impaired group.
These findings suggest an impaired Ia afferent pathway potentially underlies the defects in the interaction between postural and locomotor control post-stroke and may explain reduced ability of paretic limb support during locomotor weight-bearing in individuals post-stroke.
These results support the judicious use of bodyweight support training when first helping individuals post-stroke to regain locomotor pattern generation and weight-bearing capability.
PMCID: PMC4668037  PMID: 26629996
18.  Human genome comparison of paretic and nonparetic vastus lateralis muscle in patients with hemiparetic stroke 
Hemiparetic stroke leads to major skeletal muscle abnormalities, as illustrated by paretic leg atrophy, weakness, and spasticity. Furthermore, the hemiparetic limb muscle shifts to a fast-twitch muscle fiber phenotype with anaerobic metabolism. This study investigated whether skeletal muscle genes were altered in chronic hemiparetic stroke. The nonparetic leg muscle served as an internal control. We used Affymetrix microarray analysis to survey gene expression differences between paretic and nonparetic vastus lateralis muscle punch biopsies from 10 subjects with chronic hemiparetic stroke. Stroke latency was greater than 6 months. We found that 116 genes were significantly altered between the paretic and nonparetic vastus lateralis muscles. These gene differences were consistent with reported differences after stroke in areas such as injury and inflammation markers, the myosin heavy chain profile, and high prevalence of impaired glucose tolerance and type 2 diabetes. Furthermore, while many other families of genes were altered, the gene families with the most genes altered included inflammation, cell cycle regulation, signal transduction, metabolism, and muscle contractile protein genes. This study is an early step toward identification of specific gene regulatory pathways that might lead to these differences, propagate disability, and increase vascular disease risk.
PMCID: PMC3024241  PMID: 18566945
cell cycle; gene expression; hemiparetic stroke; inflammation; metabolism; microarray; muscle contraction; rehabilitation; skeletal muscle; transcription factors; vastus lateralis
19.  Changes in Bone Density and Geometry of the Upper Extremities after Stroke: A Case Report 
Physiotherapy Canada  2012;64(1):88-97.
Purpose: The purpose of this study was to examine changes in bone density and geometry of the forearm region and motor function of the paretic upper extremity in a person with subacute stroke. Client Description: The participant was a 48-year-old man with right hemiparesis. Intervention: Not applicable. Measures and Outcomes: The assessment of upper-extremity (UE) function and bone imaging took place at 3 months and 12 months after stroke. The participant had moderate motor impairment and severe disuse of the paretic UE 3 months after stroke. During the follow-up period, no substantial change in paretic UE function was observed. At the 12 month follow-up, the areal bone mineral density (aBMD) of the ultradistal and mid-regions of the paretic forearm, as measured by dual-energy X-ray absorptiometry, sustained a significant reduction of 7.9% and 5.9%, respectively. The non-paretic side, in contrast, had a significant 4.0% increase in aBMD of the mid-forearm and a 2.8% increase in aBMD of the total forearm. Significant findings from peripheral quantitative computed tomography were a reduction in total volumetric bone mineral density (−12.1%) and bone strength index (−20.6%) in the radius distal epiphysis on the paretic side and an increase in cortical bone mineral content (2.0%) and bone strength index (7.6%) in the radius diaphysis on the non-paretic side. Implications: After a stroke that resulted in moderate to severe UE impairment, a significant decline in bone mineral density was identified in various skeletal sites in the forearm region as the participant entered the subacute and chronic stages of recovery. The results point to the potential importance of early rehabilitative intervention in preventing unfavourable bone changes in the paretic upper limb among individuals with stroke.
PMCID: PMC3280714  PMID: 23277690
bone and bones; osteoporosis; muscles; rehabilitation; stroke; accident vasculaire cérébral; réadaptation; os; muscles; fracture; AVC
20.  Step Length Asymmetry is Representative of Compensatory Mechanisms Used in Post-Stroke Hemiparetic Walking 
Gait & posture  2011;33(4):538-543.
Post-stroke hemiparetic subjects walk with asymmetrical step lengths that are highly variable between subjects and may be indicative of the underlying impairments and compensatory mechanisms used. The goal of this study was to determine if post-stroke hemiparetic subjects grouped by step length asymmetry have similar abnormal walking biomechanics compared to non-impaired walkers. Kinematic and ground reaction force data were recorded from 55 hemiparetic subjects walking at their self-selected speed and 21 age and speed-matched non-impaired control subjects. Hemiparetic subjects were grouped by paretic step ratio, which was calculated as the paretic step-length divided by the sum of paretic and nonparetic step-lengths, into high (>0.535), symmetric (0.535–0.465) and low (<0.465) groups. Non-parametric Wilcoxin signed-rank tests were used to test for differences in joint kinetic measures between hemiparetic groups and speed-matched control subjects during late single-leg stance and pre-swing. The paretic leg ankle moment impulse was reduced in all hemiparetic subjects regardless of their paretic step ratio. The high group had increased nonparetic leg ankle plantarflexor and knee extensor moment impulses, the symmetric group had increased hip flexor moment impulses on both the paretic and nonparetic leg and the low group had no additional significant differences in joint moment impulses. These results suggest that the direction of asymmetry can be used to identify both the degree of paretic plantarflexor impairment and the compensatory mechanisms used by post-stroke hemiparetic subjects.
PMCID: PMC3085662  PMID: 21316240
Biomechanics; Post-stroke; Gait Kinetics; Rehabilitation; Symmetry
21.  Differences in Plantar Flexor Fascicle Length and Pennation Angle between Healthy and Poststroke Individuals and Implications for Poststroke Plantar Flexor Force Contributions 
Stroke Research and Treatment  2014;2014:919486.
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.
PMCID: PMC4134812  PMID: 25147753
22.  Experience with the “Good” Limb Induces Aberrant Synaptic Plasticity in the Perilesion Cortex after Stroke 
The Journal of Neuroscience  2015;35(22):8604-8610.
Following unilateral stroke, the contralateral (paretic) body side is often severely impaired, and individuals naturally learn to rely more on the nonparetic body side, which involves learning new skills with it. Such compensatory hyper-reliance on the “good” body side, however, can limit functional improvements of the paretic side. In rats, motor skill training with the nonparetic forelimb (NPT) following a unilateral infarct lessens the efficacy of rehabilitative training, and reduces neuronal activation in perilesion motor cortex. However, the underlying mechanisms remain unclear. In the present study, we investigated how forelimb movement representations and synaptic restructuring in perilesion motor cortex respond to NPT and their relationship with behavioral outcomes. Forelimb representations were diminished as a result of NPT, as revealed with intracortical microstimulation mapping. Using transmission electron microscopy and stereological analyses, we found that densities of axodendritic synapses, especially axo-spinous synapses, as well as multiple synaptic boutons were increased in the perilesion cortex by NPT. The synaptic density was negatively correlated with the functional outcome of the paretic limb, as revealed in reaching performance. Furthermore, in animals with NPT, there was dissociation between astrocytic morphological features and axo-spinous synaptic density in perilesion motor cortex, compared with controls. These findings demonstrate that skill learning with the nonparetic limb following unilateral brain damage results in aberrant synaptogenesis, potentially of transcallosal projections, and this seems to hamper the functionality of the perilesion motor cortex and the paretic forelimb.
PMCID: PMC4452558  PMID: 26041926
astrocyte; forelimb behavior; learned nonuse; motor cortex; stroke recovery; synaptic plasticity
23.  Effects of a Single Session of High Intensity Interval Treadmill Training on Corticomotor Excitability following Stroke: Implications for Therapy 
Neural Plasticity  2016;2016:1686414.
Objective. High intensity interval treadmill training (HIITT) has been gaining popularity for gait rehabilitation after stroke. In this study, we examined the changes in excitability of the lower limb motor cortical representation (M1) in chronic stroke survivors following a single session of HIITT. We also determined whether exercise-induced changes in excitability could be modulated by transcranial direct current stimulation (tDCS) enhanced with a paretic ankle skill acquisition task. Methods. Eleven individuals with chronic stroke participated in two 40-minute treadmill-training sessions: HIITT alone and HITT preceded by anodal tDCS enhanced with a skill acquisition task (e-tDCS+HIITT). Transcranial magnetic stimulation (TMS) was used to assess corticomotor excitability of paretic and nonparetic tibialis anterior (TA) muscles. Results. HIIT alone reduced paretic TA M1 excitability in 7 of 11 participants by ≥ 10%. e-tDCS+HIITT increased paretic TA M1 excitability and decreased nonparetic TA M1 excitability. Conclusions. HIITT suppresses corticomotor excitability in some people with chronic stroke. When HIITT is preceded by tDCS in combination with a skill acquisition task, the asymmetry of between-hemisphere corticomotor excitability is reduced. Significance. This study provides preliminary data indicating that the cardiovascular benefits of HIITT may be achieved without suppressing motor excitability in some stroke survivors.
PMCID: PMC5056005  PMID: 27738524
24.  Modulation of Ankle Muscle Postural Reflexes in Stroke: Influence of Weight-bearing Load 
Given the known sensorimotor deficits and asymmetric weight-bearing posture in stroke, the aim of this study was to determine whether stroke affects the modulation of standing postural reflexes with varying weight-bearing load.
Ten individuals with chronic stroke and 10 healthy older adult controls were exposed to unexpected forward and backward platform translations while standing. Three different stance conditions were imposed: increased weight-bearing load, decreased weight-bearing load, and self-selected stance. Surface EMG from bilateral ankle dorsiflexors (tibialis anterior) and extensors (gastrocnemius) were recorded and the magnitude of background muscle activity (prior to the platform translation) and postural reflex onset latency and magnitude (75 ms following reflex onset) were determined.
Load modulation of ankle extensors was found in controls and individuals with stroke. Although controls demonstrated modulation of ankle dorsiflexors to different loads, individuals with stroke did not show this modulation. Further, load did not change the onset latency of postural reflexes of the individuals with stroke.
The delayed paretic muscle onset latencies in conjunction with impaired modulation of ankle dorsiflexor postural reflexes may contribute to the instability and frequent falls observed among individuals with stroke.
The results provide some insight into standing postural reflexes following stroke.
PMCID: PMC3226800  PMID: 15546787 CAMSID: cams2000
postural control; reflex; weight-bearing; cerebrovascular accident
25.  Effects of unilateral robotic limb loading on gait characteristics in subjects with chronic stroke 
Hemiparesis after stroke often leads to impaired ankle motor control that impacts gait function. In recent studies, robotic devices have been developed to address this impairment. While capable of imparting forces to assist during training and gait, these devices add mass to the paretic leg which might encumber patients' gait pattern. The purpose of this study was to assess the effects of the added mass of one of these robots, the MIT's Anklebot, while unpowered, on gait of chronic stroke survivors during overground and treadmill walking.
Nine chronic stroke survivors walked overground and on a treadmill with and without the anklebot mounted on the paretic leg. Gait parameters, interlimb symmetry, and joint kinematics were collected for the four conditions. Repeated-measures analysis of variance (ANOVA) tests were conducted to examine for possible differences across four conditions for the paretic and nonparetic leg.
The added inertia and friction of the unpowered anklebot had no statistically significant effect on spatio-temporal parameters of gait, including paretic and nonparetic step time and stance percentage, in both overground and treadmill conditions. Noteworthy, interlimb symmetry as characterized by relative stance duration was greater on the treadmill than overground regardless of loading conditions. The presence of the unpowered robot loading reduced the nonparetic knee peak flexion on the treadmill and paretic peak dorsiflexion overground (p < 0.05).
Our results suggest that for these subjects the added inertia and friction of this backdriveable robot did not significantly alter their gait pattern.
PMCID: PMC2887457  PMID: 20492698

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