Paretic Leg Research Articles

Effects of modified constraint-induced movement therapy on the lower extremities in patients with stroke: a pilot study

Purpose: This study aimed to qualify the improvements of modified constraint-induced movement therapy (m-CIMT) on the lower limb of stroke patients via assessing the centre of mass (COM) displacement and the basic gait parameters.Methods: A total of 22 hemiplegic patients after stroke with first-time clinical cerebral infarction or haemorrhagic cerebrovascular accident were included in this study from May to December, 2014. The patients were randomly divided into m-CIMT group and the conventional therapy group (control group), and received corresponding training for five days/week for four weeks. The COM displacement and gait parameters were assessed by three-dimensional segmental kinematics method in pre-intervention and post- intervention therapy.Results: After four weeks of m-CIMT, the COM displacement on sagittal plane of paretic leg during stance phase was increased (pre: 91.04 ± 4.39 cm, post: 92.38 ± 4.58 cm, p < 0.05) and swing range of frontal plane was remarkably decreased (pre: 10.15 ± 3.05 cm, post: 7.83 ± 1.90 cm, p < 0.001). Meantime, the normalised swing range of COM in m-CIMT was superior to that in control group. Moreover, the gait parameters, including velocity (0.27 m/s), step width (0.10 m), step length (0.22 m) and swing time percentage (29.80%), were significantly improved by post-interventions of m-CIMT (p < 0.05).Conclusion: The m-CIMT intervention improves the COM displacement in sagittal and frontal plane, as well as gait parameters. These suggest that m-CIMT intervention may be feasible and effective for the rehabilitation of hemiplegic gait. Implications for RehabilitationSegmental kinematics method was used to estimate the displacement of the COM.m-CIMT interventions improved the COM displacement of patients after stroke.m-CIMT interventions improved the hemiplegic gait parameters.

Effects of concentric and eccentric control exercise on gross motor function and balance ability of paretic leg in children with spastic hemiplegia.

[Purpose] This study examines the effect of concentric and eccentric control training of the paretic leg on balance and gross motor function in children with spastic hemiplegia. [Subjects and Methods] Thirty children with spastic hemiplegia were randomly divided into experimental and control groups. In the experimental group, 20 min of neurodevelopmental therapy and 20 min of concentric and eccentric control exercise were applied to the paretic leg. In the control group, 40 min of neurodevelopmental therapy was applied. The Pediatric Balance Scale test and standing and gait items of the Gross Motor Function Measure were evaluated before and after intervention. [Results] In the experimental group, Gross Motor Function Measure and Pediatric Balance Scale scores statistically significantly increased after the intervention. The control group showed no statistically significant difference in either score after the intervention. [Conclusion] Concentric and eccentric control exercise therapy in children with spastic hemiplegia can be effective in improving gross motor function and balance ability, and can be used to solve functional problems in a paretic leg.

Lower Limb Rehabilitation Using Patient Data.

The aim of this study is to investigate the performance of a 6-DoF parallel robot in tracking the movement of the foot trajectory of a paretic leg during a single stride. The foot trajectories of nine patients with a paretic leg including both males and females have been measured and analysed by a Vicon system in a gait laboratory. Based on kinematic and dynamic analysis of a 6-DoF UPS parallel robot, an algorithm was developed in MATLAB to calculate the length of the actuators and their required forces during all trajectories. The workspace and singularity points of the robot were then investigated in nine different cases. A 6-DoF UPS parallel robot prototype with high repeatability was designed and built in order to simulate a single stride. Results showed that the robot was capable of tracking all of the trajectories with the maximum position error of 1.2 mm.

The effects of Pilates exercise training on static and dynamic balance in chronic stroke patients: a randomized controlled trial.

[Purpose] The purpose of this study was to analyze the effects of Pilates exercise on static and dynamic balance in chronic stroke patients. [Subjects and Methods] Nineteen individuals with unilateral chronic hemiparetic stroke (age, 64.7 ± 6.9 years; height, 161.7 ± 7.9 cm; weight, 67.0 ± 11.1 kg) were randomly allocated to either a Pilates exercise group (PG, n=10) or a control group (CG, n=9). The PG attended 24 exercise sessions conducted over an 8-week period (3 sessions/week). Center of pressure (COP) sway and COP velocity were measured one week before and after the exercise program and compared to assess training effects. [Results] Pilates exercise positively affected both static and dynamic balance in patients with chronic stroke. For static balance, COP sway and velocity in the medial-lateral (M-L) and anterior-posterior (A-P) directions were significantly decreased in the PG after training while no significant differences were found in the CG. For dynamic balance, measured during treadmill walking, the PG showed significantly reduced COP sway and velocity in the M-L and A-P directions for both the paretic and non-paretic leg. [Conclusions] The findings provide initial evidence that Pilates exercise can enhance static and dynamic balance in patients with chronic stroke.

Focusing on Increasing Velocity during Heavy Resistance Knee Flexion Exercise Boosts Hamstring Muscle Activity in Chronic Stroke Patients.

Background. Muscle strength is markedly reduced in stroke patients, which has negative implications for functional capacity and work ability. Different types of feedback during strength training exercises may alter neuromuscular activity and functional gains. Objective. To compare levels of muscle activity during conditions of blindfolding and intended high contraction speed with a normal condition of high-intensity knee flexions. Methods. Eighteen patients performed unilateral machine knee flexions with a 10-repetition maximum load. Surface electromyography (EMG) was recorded from the quadrics and hamstring muscles and normalized to maximal EMG (nEMG) of the nonparetic limb. Results. For the paretic leg, the speed condition showed higher values of muscle activity compared with the normal and blindfolded conditions for both biceps femoris and semitendinosus. Likewise, the speed condition showed higher co-contraction values compared with the normal and blindfolded conditions for the vastus lateralis. No differences were observed between exercise conditions for the nonparetic leg. Conclusion. Chronic stroke patients are capable of performing heavy resistance training with intended high speed of contraction. Focusing on speed during the concentric phase elicited higher levels of muscle activity of the hamstrings compared to normal and blindfolded conditions, which may have implications for regaining fast muscle strength in stroke survivors.

Effect of Leg Selection on the Berg Balance Scale Scores of Hemiparetic Stroke Survivors: A Cross-Sectional Study

ObjectiveTo examine whether selection of the nonparetic or paretic leg as the weight-bearing leg in item 13 (standing unsupported one foot in front) and item 14 (standing on one leg) of the Berg Balance Scale (BBS) influences the item scores, and thus the total score. DesignCross-sectional study. SettingUniversity-based rehabilitation laboratory. ParticipantsCommunity-dwelling people (N=63, aged ≥50y) with chronic stroke. InterventionsNot applicable. Main Outcome MeasureBBS. ResultsThe 4 BBS total scores ranged from 48.4 to 50.7. The total score was significantly lower when a participant was asked to step forward with the nonparetic leg in item 13, and stand on the paretic leg in item 14. Fewer participants received a maximum score with the BBS1 formulation than the others. In addition, the correlations with walking speed and Activities-specific Balance Confidence Scale scores were greatest with the BBS1 score. ConclusionsOur findings suggest that BBS1 was the most challenging formulation for our participants; this might serve to minimize the ceiling effect of the BBS. These findings provide a rationale for amending the BBS administration guidelines with the BBS1 formulation.

Electromyographic Comparison of Elastic Resistance and Machine Exercises for High-Intensity Strength Training in Patients With Chronic Stroke

ObjectiveTo investigate whether elastic resistance training can induce comparable levels of muscle activity as conventional machine training in patients with chronic stroke. DesignComparative study. SettingOutpatient rehabilitation facility. ParticipantsStroke patients (N=18) with hemiparesis (mean age, 57±8y). InterventionsPatients performed 3 consecutive repetitions at 10 repetition maximum of unilateral knee extension and flexion using elastic resistance and conventional machine training. Main Outcome MeasuresSurface electromyography was measured in vastus lateralis, vastus medialis, biceps femoris, and semitendinosus and was normalized to maximal electromyography (% of max) of the nonparetic leg. ResultsIn the paretic leg, agonist muscle activity ranged from 18% to 24% normalized electromyography (% of max) (nEMG) during knee flexion and from 32% to 40% nEMG during knee extension. For knee extension, vastus lateralis nEMG was higher during machine exercise than during elastic resistance exercise (40% [95% confidence interval {CI}, 33–47] vs 32% [95% CI, 25–39]; P=.003). In the nonparetic leg, agonist muscle activity ranged from 54% to 61% during knee flexion and from 52% to 68% during knee extension. For knee flexion semitendinosus nEMG was higher (61% [95% CI, 50–71] vs 54% [95% CI, 44–64]; P=.016) and for knee extension vastus medialis nEMG was higher (68% [95% CI, 60–76] vs 56% [95% CI, 48–64]; P<.001) during machine exercise than during elastic resistance exercise. By contrast, antagonist coactivation was significantly higher during knee flexion when performed using elastic resistance compared with the machine. Lastly, there were no differences in perceived exertion between exercise modalities. ConclusionsMachine training appears to induce slightly higher levels of muscle activity in some of the investigated muscles compared to elastic resistance during lower limb strength training in patients with chronic stroke. The higher level of coactivation during knee flexion when performed using elastic resistance suggests that elastic resistance exercises are more difficult to perform. This is likely due to a higher level of movement instability.

Locomotor Adaptability Task Promotes Intense and Task-Appropriate Output From the Paretic Leg During Walking

ObjectiveTo test the hypothesis that participants with stroke will exhibit appropriate increase in muscle activation of the paretic leg when taking a long step with the nonparetic leg compared to during steady-state walking, with a consequent increase in biomechanical output and symmetry during the stance phase of the modified gait cycle. DesignSingle-session observational study. SettingClinical research center in an outpatient hospital setting. ParticipantsAdults with chronic poststroke hemiparesis (N=15). InterventionsParticipants walked on an instrumented treadmill while kinetic, kinematic, and electromyogram data were recorded. Participants performed steady-state walking and a separate trial of the long-step adaptability task in which they were instructed to intermittently take a longer step with the nonparetic leg. Main Outcome MeasuresForward progression, propulsive force, and neuromuscular activation during walking. ResultsParticipants performed the adaptability task successfully and demonstrated greater neuromuscular activation in appropriate paretic leg muscles, particularly increased activity in paretic plantarflexor muscles. Propulsion and forward progression by the paretic leg were also increased. ConclusionsThese findings support the assertion that the nonparetic long-step task may be effective for use in poststroke locomotor rehabilitation to engage the paretic leg and promote recovery of walking.

Effects of implantable peroneal nerve stimulation on gait quality, energy expenditure, participation and user satisfaction in patients with post-stroke drop foot using an ankle-foot orthosis.

To investigate whether an implantable functional electrical stimulation (FES) system of the common peroneal nerve (ActiGait®) improves relevant aspects of gait in chronic stroke patients with a drop foot typically using an ankle-foot orthosis (AFO). Ten community-dwelling patients participated, of whom eight patients could be analysed. Gait quality (kinematic, kinetic, and spatiotemporal characteristics) during a 10-meter comfortable walk test, normalised net energy expenditure during a 6-minute walk test, participation (physical activity and stroke impact) and user satisfaction were tested before implantation and at various moments after FES-system activation up to 26 weeks. Walking with FES yielded increased maximum paretic ankle plantarflexion (FES: -0.12; AFO: -4.79°, p < 0.01), higher paretic peak ankle power (FES: 1.46; AFO: 0.98 W/kg, p < 0.05) and better step length symmetry (FES: 14.90; AFO: 21.45% , p < 0.05). User satisfaction was higher for FES, but was unrelated to objective gait improvements. Energy expenditure and participation did not change. Implantable FES improved the use of residual ankle plantarflexion motion, ankle power of the paretic leg and step length symmetry compared to using an AFO, however, not resulting in decreased energy expenditure or improved participation. User satisfaction was highest with FES, but this was not related to the observed gait improvements.

Patterns of muscle coordination during stepping responses post-stroke

This study compared self-induced stepping reactions of seventeen participants after stroke and seventeen controls. Surface electromyographic (EMG) signals were recorded bilaterally from the soleus (SOL), tibialis anterior (TA), biceps femoris (BF) and rectus femoris (RF) muscles. Principal component analysis (PCA) was used to reduce the data into muscle activation patterns and examine group differences (paretic, non-paretic, control leg). The first principal component (PC1) explained 46.7% of the EMG signal of the stepping leg. Two PCs revealed distinct activation features for the stepping paretic leg: earlier TA onset at step initiation and earlier BF and SOL onset at mid-step. For the stance leg, PC1 explained 44.4% of the EMG signal and significant differences were found in the non-paretic leg compared to paretic (p<0.001) and control (p<0.001). In PC1, at step onset the BF and SOL EMG and the RF and TA EMG were increased over the latter half of the step. No PC loadings were distinct for the paretic leg during stance, however differences were found in the non-paretic leg: earlier TA burst and increased BF and SOL EMG at step initiation. The results suggest impairments in the paretic leg when stepping and compensatory strategies in the non-paretic stance leg.

Transcranial Direct Current Stimulation of the Leg Motor Cortex Enhances Coordinated Motor Output During Walking With a Large Inter-Individual Variability

Transcranial direct current stimulation (tDCS) can augment force generation and control in single leg joints in healthy subjects and stroke survivors. However, it is unknown whether these effects also result in improved force production and coordination during walking and whether electrode configuration influences these effects. We investigated the effect of tDCS using different electrode configurations on coordinated force production during walking in a group of healthy subjects and chronic stroke survivors. Ten healthy subjects and ten chronic stroke survivors participated in a randomized double-blinded crossover study. Subjects walked on an instrumented treadmill before and after 10 minutes of uni-hemispheric (UNI), dual-hemispheric (DUAL) or sham tDCS applied to the primary motor cortex. tDCS responses showed large inter-individual variability in both subject populations. In healthy subjects tDCS enhanced the coordinated output during walking as reflected in an increased positive work generation during propulsion. The effects of DUAL tDCS were clearer but still small (4.4% increase) compared to UNI tDCS (2.8% increase). In the chronic stroke survivors no significant effects of tDCS in the targeted paretic leg were observed. tDCS has potential to augment multi-joint coordinated force production during walking. The relative small contribution of the motor cortex in controlling walking might explain why the observed effects are rather small. Furthermore, a better understanding of the inter-individual variability is needed to optimize the effects of tDCS in healthy but especially stroke survivors. The latter is a prerequisite for clinical applicability.

A novel and simple test of gait adaptability predicts gold standard measures of functional mobility in stroke survivors

BackgroundAlthough there is evidence that stroke survivors have reduced gait adaptability, the underlying mechanisms and the relationship to functional recovery are largely unknown. We explored the relationships between walking adaptability and clinical measures of balance, motor recovery and functional ability in stroke survivors. MethodsStroke survivors (n=42) stepped to targets, on a 6m walkway, placed to elicit step lengthening, shortening and narrowing on paretic and non-paretic sides. The number of targets missed during six walks and target stepping speed was recorded. Fugl–Meyer (FM), Berg Balance Scale (BBS), self-selected walking speed (SWWS) and single support (SS) and step length (SL) symmetry (using GaitRite when not walking to targets) were also assessed. Stepwise multiple-linear regression was used to model the relationships between: total targets missed, number missed with paretic and non-paretic legs, target stepping speed, and each clinical measure. ResultsRegression revealed a significant model for each outcome variable that included only one independent variable. Targets missed by the paretic limb, was a significant predictor of FM (F(1,40)=6.54, p=0.014,). Speed of target stepping was a significant predictor of each of BBS (F(1,40)=26.36, p<0.0001), SSWS (F(1,40)=37.00, p<0.0001). No variables were significant predictors of SL or SS asymmetry. DiscussionSpeed of target stepping was significantly predictive of BBS and SSWS and paretic targets missed predicted FM, suggesting that fast target stepping requires good balance and accurate stepping demands good paretic leg function. The relationships between these parameters indicate gait adaptability is a clinically meaningful target for measurement and treatment of functionally adaptive walking ability in stroke survivors.

Using surface electromyography to guide the activation during motor-evoked potential measurement: An activation control method for follow-up studies

Objective: This study evaluated the reliability and validity of a convenient method that uses the real-time feedback surface electromyography (sEMG) to control muscle activation while measuring the MEP recorded from the quadriceps muscle in patients with stroke.Methods: It measured the MEP parameters as well as the clinical assessment at initial test. Participants were directed to adjust their quadriceps contraction to extend the knee isometrically and maintain the EMG amplitude at 0.2 mV. MEPs were measured 2 weeks after the initial test again to assess the reliability of this measurement.Results: A good test–re-test reliability was demonstrated with an intra-class correlation coefficient (ICC) > 0.8 for the motor threshold and a moderate reliability (ICC > 0.6) for the MEP latency and MEP amplitude, for both paretic and non-paretic legs. Patients with present MEPs had significantly higher scores in muscle power, the Fugl-Meyer assessment, the balance sub-scale of performance-oriented mobility assessment and the Barthel index; and lower NIHSS scores than those of patients with absent MEPs (all p < 0.05).Conclusion: The sEMG-guided low level muscle activation is suitable for MEP assessment in patients with leg weakness after a stroke and may be used for long-term follow-up studies.

Locomotor asymmetry in post-stroke individuals: Why and how to use the split-belt treadmill to improve the gait performance

The recovery of gait symmetry post-stroke tends to be more challenging compared to other functional deficits when using conventional therapy. However, investigations on walking at unequal speeds on a split-belt treadmill have revealed improvements in symmetry of spatial and temporal gait parameters. The main objective of this study was to identify the causes of changes in spatio-temporal parameters by quantifying net joint moments and muscular levels of effort in the lower limbs during different walking conditions on a split-belt treadmill. Twenty individuals with chronic stroke and a mean age of 49 (± 13) years and 10 age-matched controls walked on an instrumented split-belt treadmill under three gait periods: (1) baseline (tied-belt); (2) adaptation (split-belt); and (3) post-adaptation (tied-belt). Participants post-stroke performed the protocol with the paretic and non-paretic leg on the faster belt when belts were split. Kinematic data were recorded with the Optotrak system and ground reaction forces were collected via the instrumented split-belt treadmill. The dynamic inverse gave the joint moments while levels of effort were assessed with the muscular utilization ratio (ratio of walking moment relative to the muscle's maximal capability). Repeated measures ANOVA and t -tests were used to compare the variables during the three periods. Pearson correlations were used to assess the relationships between asymmetries in these parameters. The condition with the shorter step on the fast belt improved the step length symmetry. Placing the paretic limb on the slow belt increased the plantar flexion moment in post-adaptation and that such increase was correlated with the increase in controlateral step length. A more symmetrical gait pattern (temporal or spatial) following walking on the split-belt treadmill required high levels of effort (over 85%) in paretic plantar flexors. Results also revealed that healthy individuals and patients had different ability to detect asymmetry. These results suggest that muscle strength and muscular level of effort, mainly in paretic plantar flexors, need to be considered to use the split-belt treadmill in the adaptation (split-belt) period. The classification of patients into subgroups according to their sensorimotor deficits and gait asymmetries is an important aspect to consider with this type of training.

Stay Focused! The Effects of Internal and External Focus of Attention on Movement Automaticity in Patients with Stroke.

Dual-task performance is often impaired after stroke. This may be resolved by enhancing patients’ automaticity of movement. This study sets out to test the constrained action hypothesis, which holds that automaticity of movement is enhanced by triggering an external focus (on movement effects), rather than an internal focus (on movement execution). Thirty-nine individuals with chronic, unilateral stroke performed a one-leg-stepping task with both legs in single- and dual-task conditions. Attentional focus was manipulated with instructions. Motor performance (movement speed), movement automaticity (fluency of movement), and dual-task performance (dual-task costs) were assessed. The effects of focus on movement speed, single- and dual-task movement fluency, and dual-task costs were analysed with generalized estimating equations. Results showed that, overall, single-task performance was unaffected by focus (p = .341). Regarding movement fluency, no main effects of focus were found in single- or dual-task conditions (p’s ≥ .13). However, focus by leg interactions suggested that an external focus reduced movement fluency of the paretic leg compared to an internal focus (single-task conditions: p = .068; dual-task conditions: p = .084). An external focus also tended to result in inferior dual-task performance (β = -2.38, p = .065). Finally, a near-significant interaction (β = 2.36, p = .055) suggested that dual-task performance was more constrained by patients’ attentional capacity in external focus conditions. We conclude that, compared to an internal focus, an external focus did not result in more automated movements in chronic stroke patients. Contrary to expectations, trends were found for enhanced automaticity with an internal focus. These findings might be due to patients’ strong preference to use an internal focus in daily life. Future work needs to establish the more permanent effects of learning with different attentional foci on re-automating motor control after stroke.

HAL® exoskeleton training improves walking parameters and normalizes cortical excitability in primary somatosensory cortex in spinal cord injury patients.

BackgroundReorganization in the sensorimotor cortex accompanied by increased excitability and enlarged body representations is a consequence of spinal cord injury (SCI). Robotic-assisted bodyweight supported treadmill training (BWSTT) was hypothesized to induce reorganization and improve walking function.ObjectiveTo assess whether BWSTT with hybrid assistive limb® (HAL®) exoskeleton affects cortical excitability in the primary somatosensory cortex (S1) in SCI patients, as measured by paired-pulse somatosensory evoked potentials (ppSEP) stimulated above the level of injury.MethodsEleven SCI patients took part in HAL® assisted BWSTT for 3 months. PpSEP were conducted before and after this training period, where the amplitude ratios (SEP amplitude following double pulses - SEP amplitude following single pulses) were assessed and compared to eleven healthy control subjects. To assess improvement in walking function, we used the 10-m walk test, timed-up-and-go test, the 6-min walk test, and the lower extremity motor score.ResultsPpSEPs were significantly increased in SCI patients as compared to controls at baseline. Following training, ppSEPs were increased from baseline and no longer significantly differed from controls. Walking parameters also showed significant improvements, yet there was no significant correlation between ppSEP measures and walking parameters.ConclusionsThe findings suggest that robotic-assisted BWSTT with HAL® in SCI patients is capable of inducing cortical plasticity following highly repetitive, active locomotive use of paretic legs. While there was no significant correlation of excitability with walking parameters, brain areas other than S1 might reflect improvement of walking functions. EEG and neuroimaging studies may provide further information about supraspinal plastic processes and foci in SCI rehabilitation.

Effects of weight-shift training on walking ability, ambulation, and weight distribution in individuals with chronic stroke: a pilot study

Background: People with gait difficulties after a stroke usually have an asymmetrical gait and slower gait speed than age-matched controls. These difficulties restrict people with stroke in their daily life activities.Objective: This pilot study sought to evaluate the effects of weight-shift training on gait, weight distribution in standing, and ambulation in people with gait difficulties after a stroke.Methods: Ten subjects with chronic stroke (3–11 years since insult) and remaining gait difficulties participated in a 3-week weight-shift training program. Spatial and temporal gait parameters were assessed pre-, post-, and 3-month post-training with a motion analysis system. Weight distribution was assessed with force plates and ambulation with the Swedish version of the Clinical Outcome Variables Scale (S-COVS). Wilcoxon signed-rank tests were used to explore differences between test occasions.Results: Significant changes were seen between pre-and post-tests in decreased stance time on the non-paretic leg (P = 0.005) and increased score on the S-COVS (P = 0.043). At the 3-month follow-up test, the subjects had also increased their gait speed significantly (P = 0.037). Standing weight distribution did not change between pre- and post-tests (P = 0.575), but between the pre-and follow-up tests it shifted from the paretic leg to the non-paretic (P = 0.007).Conclusion: Weight-shift training seems to improve gait and ambulation in subjects with chronic stroke, but not with standing weight distribution. However, this pilot study has several limitations and a larger sample size with a control group is necessary.

Impaired regulation post-stroke of motor unit firing behavior during volitional relaxation of knee extensor torque assessed using high density surface EMG decomposition.

The purpose of this study was to use high density surface EMG recordings to quantify stroke-related abnormalities in motor unit firing behavior during repeated sub-maximal knee extensor contractions. A high density surface EMG system (sEMG) was used to record and extract single motor unit firing behavior in the vastus lateralis muscle of 6 individuals with chronic stroke and 8 controls during repeated sub-maximal isometric knee extension contractions. Paretic motor unit firing rates were increased with subsequent contractions (6.19±0.35 pps vs 7.89±0.66 pps, P <; 0.05) during task phases of torque decline as compared to controls (6.95±0.40 pps vs 6.68±0.41 pps). In addition, corresponding rates of torque decline were decreased for the paretic leg as compared to the non-paretic leg. These results suggest that regulation of declining forces may be impaired post stroke due to prolonged firing of paretic motor units.

Atypical cortical drive during activation of the paretic and nonparetic tibialis anterior is related to gait deficits in chronic stroke

ObjectiveThe role of cortical drive in stroke recovery for the lower extremity remains ambiguous. The purpose of this study was to investigate the relationship between cortical drive and gait speed in a group of stroke survivors. MethodsEighteen individuals with stroke were dichotomized into fast or slow walking groups. Transcranial magnetic stimulation (TMS) was used to collect motor evoked potentials (MEPs) from the tibialis anterior of each lower extremity during rest, paretic muscle contractions, and nonparetic muscle contractions. An asymmetry-index (AI) was calculated using motor thresholds and compared between groups. The average MEP of the paretic leg during TMS at maximal intensity (MEP100) for each condition was compared within and between groups. ResultsA significant positive correlation was found between AI and walking speed. Slow-walkers had greater MEP100s during the nonparetic contraction than during the paretic contraction or rest conditions. In contrast, fast-walkers had greatest MEP100s during the paretic contraction. ConclusionsAlterations in the balance of corticomotor excitability occur in the lower extremity of individuals with poor motor recovery post-stroke. This atypical cortical drive is dependent on activation of the unaffected hemisphere and contraction of the nonparetic leg. SignificanceUnderstanding mechanisms underlying motor function can help to identify specific patient deficits that impair function.

Effects of Vibration Intensity, Exercise, and Motor Impairment on Leg Muscle Activity Induced by Whole-Body Vibration in People With Stroke.

Whole-body vibration (WBV) has increasingly been used as an adjunct treatment in neurological rehabilitation. However, how muscle activation level changes during exposure to different WBV protocols in individuals after stroke remains understudied. The purpose of this study was to examine the influence of WBV intensity on the magnitude of biceps femoris (BF) and tibialis anterior (TA) muscle activity and its interaction with exercise and with severity of motor impairment and spasticity among individuals with chronic stroke. Each of the 36 individuals with chronic stroke (mean age=57.3 years, SD=10.7) performed 8 different static exercises under 3 WBV conditions: (1) no WBV, (2) low-intensity WBV (frequency=20 Hz, amplitude=0.60 mm, peak acceleration=0.96g), and (3) high-intensity WBV (30 Hz, 0.44 mm, 1.61g). The levels of bilateral TA and BF muscle activity were recorded using surface electromyography (EMG). The main effect of intensity was significant. Exposure to the low-intensity and high-intensity protocols led to a significantly greater increase in normalized BF and TA muscle electromyographic magnitude in both legs compared with no WBV. The intensity × exercise interaction also was significant, suggesting that the WBV-induced increase in EMG activity was exercise dependent. The EMG responses to WBV were similar between the paretic and nonparetic legs and were not associated with level of lower extremity motor impairment and spasticity. Leg muscle activity was measured during static exercises only. Adding WBV during exercise significantly increased EMG activity in the TA and BF muscles. The EMG responses to WBV in the paretic and nonparetic legs were similar and were not related to degree of motor impairment and spasticity. The findings are useful for guiding the design of WBV training protocols for people with stroke.