Gait Velocity and Joint Power Generation After Stroke: Contribution of Strength and Balance

Overhead support systems differentially affect gait analysis of overground and treadmill walking

BACKGROUND

Overhead support or catch systems are frequently used in gait studies involving clinical populations to ensure participant safety. These systems remain slack when the participant is upright and therefore are assumed to not interfere with gait biomechanics. However, these systems follow participant's transverse motion during walking via rail systems, which could produce additional inertial and frictional forces that affect gait biomechanics.

OBJECTIVE

Quantify the influence of overhead support systems on gait biomechanics during treadmill and overground walking.

METHODS

We recruited fifteen uninjured adults to perform treadmill and overground walking. In each of these walking conditions, we varied each participant's walking speed (80, 100, and 120 % of preferred speed) and attachment to an overhead support system. We measured the participants' joint angles, moments and ground reaction forces using a three-dimensional motion capture system and an instrumented treadmill built into an overground walkway. For overground and treadmill walking, we examined changes in each biomechanical variable across speed and harness conditions using one-dimensional statistical parametric mapping (spm1d).

RESULTS

During overground walking, the overhead support system altered ground reaction forces, joint kinematics, and moments, and these effects became more pronounced with increased speed. During treadmill walking, we found very few changes in gait biomechanics resulting from the harness.

CONCLUSIONS

These results caution the use of experimental paradigms involving overground walking when an overhead support is required, although these results may be less pronounced in clinical populations with slower walking speeds. Overhead support systems can be used during treadmill walking without affecting biomechanical measurements.

Reliability of ankle dorsiflexor muscle strength, rate of force development, and tibialis anterior electromyography after stroke

Background

Measures of hemiparetic ankle dorsiflexor muscle strength and rate of force development (RFD) are often used to determine the efficacy of rehabilitation interventions after stroke. However, evidence supporting the reliability of these measures is limited. This brief report provides a secondary analysis investigating the between-session reliability of isometric ankle dorsiflexor muscle strength, rate of force development (RFD), and tibialis anterior electromyography (TA EMG), in people with chronic stroke.

Method

Participants (n=15) completed three maximal isometric contractions of the ankle dorsiflexor muscles as fast as possible using a rigid dynamometer. Tests were repeated seven days later. Outcomes included ankle dorsiflexor isometric maximal voluntary contraction (MVC), RFD in the first 200ms (RFD200ms), time to reach 90% MVC, and peak TA EMG. Data were analysed for 13 participants using intra-class correlation coefficients (ICC) and standard error of the measure percentage (SEM%).

Results

Reliability was higher when analysing the mean of three trials rather than the best of three trials. There was excellent reliability for isometric dorsiflexor MVC (ICC 0.97 [95% CI 0.92, 0.99], SEM% 7%). However, for other outcomes, while the ICC indicated good reliability, the lower bound of the 95% confidence interval of the ICC fell in the moderate range for TA EMG (ICC 0.86 [95% CI 0.60, 0.96], SEM% 25%) and time to reach 90% MVC (ICC 0.8 [95% CI 0.53, 0.93], SEM% 23%) and in the poor range for dorsiflexor RFD200ms (ICC 0.79 [95% CI 0.48, 0.92], SEM% 24%).

Conclusion

The findings raise concerns about the reliability of measures of rapid force production in the dorsiflexor muscles after stroke. Given the functional significance of the ankle dorsiflexors, larger studies should be conducted to further investigate these concerns and explore reliable methods for measuring rapid force production in the hemiparetic dorsiflexor muscles.

Differences in kinetic factors affecting gait speed between lesion sides in patients with stroke

The differences in kinetic mechanisms of decreased gait speed across brain lesion sides have not been elucidated, including the arrangement of motor modules reflected by kinetic interjoint coordination. The purpose of this study was to elucidate the differences in the kinetic factors of slow gait speed in patients with stroke on the lesion sides. A three-dimensional motion analysis system was employed to assess joint moment in the lower limb and representative gait parameters in 32 patients with right hemisphere brain damage (RHD) and 38 patients with left hemisphere brain damage (LHD) following stroke as well as 20 healthy controls. Motor module composition and timing were determined using principal component analysis based on the three joint moments in the lower limb in the stance phase, which were the variances accounted for principal components (PCs) and the peak timing in the time series of PCs. A stepwise multiple linear regression analysis was performed to identify the most significant joint moment and PC-associated parameter in explaining gait speed. A negligible difference was observed in age, weight, height, and gait speed among patients with RHD and LHD and controls. The following factors contributed to gait speed: in patients with RHD, larger ankle plantarflexion moment on the paretic (p = 0.001) and nonparetic (p = 0.002) sides and ankle dorsiflexion moment on the nonparetic side (p = 0.004); in patients with LHD, larger ankle plantarflexion moment (p < 0.001) and delayed peak timing of the first PC (p = 0.012) on the paretic side as well as ankle dorsiflexion moment on the nonparetic side (p < 0.001); in the controls, delayed peak timing of the first PC (p = 0.002) on the right side and larger ankle dorsiflexion moment (p = 0.001) as well as larger hip flexion moment on the left side (p = 0.023). The findings suggest that the kinetic mechanisms of gait speed may differ among patients with RHD following patients with stroke with LHD, and controls.

Comparison of biomechanical parameters in lower limb joints of stroke patients according to conventional evaluation scores during level walking

Objective: Patients with chronic stroke capable of independent gait were classified into functional ambulation category (FAC) 4 or 5, and the kinetic and kinematic data on their lower limb joints on the affected and unaffected sides were compared with that of healthy individuals. Finally, the qualitative changes in the gait of patients with stroke were investigated based on the differences in FAC scores. Methods: Twelve healthy participants and 19 patients with stroke capable of independent gait were included. The three-dimensional (3D) motion analysis and conventional assessment were conducted for all patients with stroke. Results: The FAC 5 group exhibited a larger range of motion (ROM) than the FAC 4 group in knee and hip joints on the affected side and only in the hip on the unaffected side. In the FAC 5 group, ROM differences in the healthy group on either the affected or unaffected side were absent. The peak of the hip flexion moment on the affected side in both the FAC 4 and 5 groups was smaller than that in the healthy group and in the FAC 4 group on the unaffected side. The absorption power minimum on the affected side was smaller only in the FAC 4 group than that in the healthy group and was larger in the FAC 5 group than that in the FAC 4 group. On the unaffected side, the absorption power minimum was smaller only in the FAC 4 group than that in the healthy group. Conclusion: Functional differences in gait were found in patients classified based on conventional evaluation capable of independent gait after post-stroke rehabilitation. Patients may not exhibit complete recovery in the kinetic indices even if they are judged to be normal in the conventional evaluation, and the kinematic gait indices indicate recovery. Evaluating kinetic indices in addition to kinematic indices is necessary, and joint power may be an especially useful index.

Clinical Factors Associated With Balance Function in the Early Subacute Phase After Stroke

OBJECTIVE

The aim of the study was to investigate the key factors of balance function in the early subacute phase after stroke.

DESIGN

Ninety-four stroke patients were included. Multiple variables were evaluated, including demographic factors, clinical variables (stroke type; lesion site; Mini-Mental State Examination; motor strength of the hip, knee, and ankle joints; Fugl-Meyer Assessment of lower extremity), neurophysiological variables (amplitude ratio of somatosensory evoked potential of the tibial nerves), and laterality index of fractional anisotropy of the corticospinal tract using diffusion tensor imaging. Balance function was measured using the Berg Balance Scale.

RESULTS

The Berg Balance Scale score was significantly negatively correlated with age and laterality index of fractional anisotropy and positively correlated with Mini-Mental State Examination; Fugl-Meyer Assessment of lower extremity; motor strength of the affected hip, knee, and ankle joint; and somatosensory evoked potential amplitude ratio (P < 0.05). The abnormal somatosensory evoked potential group and poor integrity of the corticospinal tract group showed significantly decreased Berg Balance Scale scores. In multivariable logistic regression analysis, age, Fugl-Meyer Assessment of lower extremity score, and ankle plantar flexion strength were significantly associated with balance function (odds ratios = 0.919, 1.181, and 15.244, respectively, P < 0.05).

CONCLUSIONS

Higher age, severe initial motor impairment, and strength of the affected lower limb muscles, especially the ankle plantar flexor, are strongly associated with poor balance function early after stroke.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME.

CME OBJECTIVES

Upon completion of this article, the reader should be able to: (1) Enhance ability to evaluate motor and balance function of stroke patients by learning common assessment tools including clinical tests, neurophysiological and neuroimaging studies; (2) Explain the important factors associated with balance function impairment in early subacute stroke patients; and (3) Enhance planning rehabilitation strategies for improvement of balance function according to recovery stage after stroke.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Rate of torque development of paretic lower limb is an excellent predictor of walking speed in chronic stroke individuals

BACKGROUND

Walking speed discriminates levels of functionality in stroke survivors, but its relationship with neuromuscular parameters remains unclear. We aimed to (1) verify relationships between walking speed, peak torque, and rate of torque development in individuals with chronic stroke and (2) investigate whether adjusting the predictive model for assistive device use and lower limb motor function improves its accuracy.

METHODS

Twenty-nine stroke survivors (time post-stroke ≥6 months) were assessed for walking speed, motor function, torque of knee extensors, and rate of torque development. Hierarchical multiple regression was conducted to infer the contribution of assistive device use and lower limb motor function in the proportion of variance in walking speed explained by neuromuscular parameters. Adequacy of regression models was verified using Shapiro-Wilk test and visual inspection of histograms.

FINDINGS

Rate of torque development measures presented higher coefficients of determination (R² = 0.399-0.457) than peak torque (R² = 0.333). However, no differences were observed between correlation coefficients (P > 0.05). When adjusted for assistive device use and lower limb motor function, coefficients of determination of all neuromuscular parameters were improved (P < 0.05). Regression models showed good adequacy.

INTERPRETATION

Peak torque and rate of torque development from knee extensors are adequate predictors of walking speed in stroke survivors. Adjusting predictive models for assistive device use and lower limb motor function increases predictive capacity. These findings may have repercussions for assessing chronic stroke individuals and developing treatment strategies.

The Relationship Between Strength of the Affected Leg and Walking Speed After Stroke Varies According to the Level of Walking Disability: A Systematic Review

OBJECTIVE

The objectives of this review were to determine the relationship between muscle strength of the affected leg and walking speed after stroke and whether this relationship varied according to muscle group or level of walking disability.

METHODS

This systematic review with meta-analysis focused on observational studies of adult survivors of stroke. Muscle strength had to be measured as maximum voluntary force production during an isometric contraction of the affected leg. Walking had to be measured as walking speed. Studies had to report correlations between muscle strength and walking speed.

RESULTS

Thirty studies involving 1001 participants were included. Pooled mean correlations between muscle strength of the affected leg and walking speed was 0.51 (95% CI = 0.45 to 0.57). Pooled correlations between the strength of individual muscle groups and walking speed ranged from 0.42 (for the hip abductors) to 0.57 (for the ankle dorsiflexors). The correlation between level of walking disability and the mean correlation between muscle strength and walking speed was -0.70 (95% CI = -0.42 to -0.86).

CONCLUSION

After stroke, there is a strong relationship between strength of the affected leg and walking speed, with little variability across individual muscle groups. However, the level of walking disability of people with stroke does make a difference such that the more disabled people are, the stronger the relationship is between strength of the affected leg and walking speed.

IMPACT

This study suggests that the strength of all muscles of the affected leg is important for walking after stroke. It appears that increasing strength in the affected leg could be most important in people who are more disabled.

LAY SUMMARY

After stroke, the speed at which a person can walk is highly associated with the muscle strength of their affected leg. In people whose walking speed is severely affected, this association is stronger, and the physical therapist might focus on strengthening that leg so the individual can walk faster.

Rest Intervals during Virtual Reality Gaming Augments Standing Postural Sway Disturbance

Immersive virtual reality (VR) can cause acute sickness, visual disturbance, and balance impairment. Some manufacturers recommend intermittent breaks to overcome these issues; however, limited evidence examining whether this is beneficial exists. The aim of this study was to examine whether taking breaks during VR gaming reduced its effect on postural sway during standing balance assessments. Twenty-five people participated in this crossover design study, performing 50 min of VR gaming either continuously or with intermittent 10 min exposure/rest intervals. Standing eyes open, two-legged balance assessments were performed immediately pre-, immediately post- and 40 min post-exposure. The primary outcome measure was total path length; secondary measures included independent axis path velocity, amplitude, standard deviation, discrete and continuous wavelet transform-derived variables, and detrended fluctuation analysis. Total path length was significantly (p < 0.05) reduced immediately post-VR gaming exposure in the intermittent rest break group both in comparison to within-condition baseline values and between-condition timepoint results. Conversely, it remained consistent across timepoints in the continuous exposure group. These changes consisted of a more clustered movement speed pattern about a lower central frequency, evidenced by signal frequency content. These findings indicate that caution is required before recommending rest breaks during VR exposure until we know more about how balance and falls risk are affected.

Prediction equation of hip external rotators maximum torque in healthy adults and older adults using the measure of hip extensors maximum torque

BACKGROUND

The use of predictive equation of muscular torque can reduce physical effort and time spent during evaluation.

OBJECTIVES

To establish, validate, and test the accuracy of a prediction equation to estimate the hip external rotators (HER) torque in adults and older adults by means of hip extensors (HEX) torque measurement.

METHODS

Eighty-three healthy adults (development set) were assessed to test the association of HEX and HER torques and to establish the prediction equation. A separate 36 adults and 15 older adults (validation sets) were assessed to test the ability of the equation to estimate HER torque. Hip isometric strength was assessed by a handheld dynamometer.

RESULTS

Simple linear regression analysis revealed that HEX torque was associated with HER torque (r=0.80; p<0.0001), resulting in the following prediction equation: HERtorque=-0.02+(0.58 * HEXtorque). Paired t-test revealed no difference between directly measured and predicted values of HER torque in adults (mean difference=0.02; 95% CI=-0.115, 0.072) and older adults (mean difference=0.05; 95% CI=-0.02, 0.12).

CONCLUSION

The HEX and HER torques were strongly correlated. The prediction equation was valid, accurate, and can be used to estimate HER muscle strength in healthy adults and older adults, requiring only the direct measurement of HEX torque.

Relationship between Nintendo's Wii balance board derived variables and clinical balance scores in individuals with stroke

BACKGROUND

The Wii Balance Board (WBB) is widely studied as a balance testing platform and is reliable in detecting changes in the body's center of pressure (COP). However, the relationship between WBB derived measures and clinical tests of balance is currently unknown.

RESEARCH QUESTION

To investigate the association between static and dynamic COP measures from the WBB with balance tests commonly used in chronic stroke.

METHODS

This retrospective study included sixty-nine individuals with stroke who performed the Berg Balance Score (BBS), the Mini-BESTest and WBB assessments as a part of their baseline measurements. The WBB assessments included body weight symmetry and a dynamic target matching task that measured Reaction Time (RT) and Completion Time (CT).

RESULTS

Body weight symmetry performed with eyes open was significantly different between participants who were classified as high and moderate balance using the Mini-BESTest (p = 0.03). A significant negative linear correlation was observed between the BBS and CT (rho = -0.29, p = 0.021) and between the Mini-BESTest and RT (rho=-0.246, p = 0.05).

SIGNIFICANCE

We provide preliminary but weak evidence supporting the relationship between WBB derived variables in relevance to the BBS and Mini-BESTest. Further research is needed to fully understand the clinical utility of the WBB especially in a larger sample and to generalize these results to stroke survivors at all levels of ability.

Five times sit-to-stand following stroke: Relationship with strength and balance

BACKGROUND

Rising from a chair is an important functional measure after stroke. Originally developed as a measure of lower-limb strength, the five times sit-to-stand test has shown associations with other measures of impairment, such as balance ability. We aimed to compare strength and balance in their relationship with the five times sit-to-stand test following stroke.

METHODS

Sixty-one participants following stroke were recruited from two hospitals in this cross-sectional observational study. Participants underwent assessment of the five times sit-to-stand (measured with a stopwatch), bilateral lower-limb muscle strength of seven individual muscle groups (hand-held dynamometry), and standing balance (computerised posturography). Partial correlations (controlling for body mass and height) were used to examine bivariate associations. Regression models with partial F-tests (including pertinent covariates) compared the contribution of strength (both limbs) and balance to five times sit-to-stand time.

RESULTS

The strength of the majority of lower-limb muscle groups (6/7) on the paretic side had a significant (P < 0.05) partial correlation with five times sit-to-stand time (r = -0.34 to -0.47) as did all balance measures (r = -0.27 to -0.56). In our regression models, knee extensor strength, total path length, and anteroposterior path velocity provided the largest contribution to five times sit-to-stand over covariates amongst strength and balance measures (R² = 16.6 to 17.9 %). Partial F-tests revealed that both lower-limb strength and balance contribute to five times sit-to-stand time independent of each other. A regression model containing knee extensor strength and anteroposterior path velocity accounted for 25.5 % of the variance in five times sit-to-stand time over covariates.

CONCLUSIONS

The strength of the knee extensor muscle group along with measures of standing balance ability (total path length and anteroposterior path velocity) both independently contribute to five times sit-to-stand time. Further research is required to examine how other important impairments post stroke impact five times sit-to-stand performance.

A randomized controlled trial of motor imagery combined with structured progressive circuit class therapy on gait in stroke survivors

Structured Progressive Circuit Class Therapy (SPCCT) was developed based on task-oriented therapy, providing benefits to patients’ motivation and motor function. Training with Motor Imagery (MI) alone can improve gait performance in stroke survivors, but a greater effect may be observed when combined with SPCCT. Health education (HE) is a basic component of stroke rehabilitation and can reduce depression and emotional distress. Thus, this study aimed to investigate the effect of MI with SPCCT against HE with SPCCT on gait in stroke survivors. Two hundred and ninety stroke survivors from 3 hospitals in Yangon, Myanmar enrolled in the study. Of these, 40 stroke survivors who passed the selection criteria were randomized into an experimental (n = 20) or control (n = 20) group. The experimental group received MI training whereas the control group received HE for 25 minutes prior to having the same 65 minutes SPCCT program, with both groups receiving training 3 times a week over 4 weeks. Temporo-spatial gait variables and lower limb muscle strength of the affected side were assessed at baseline, 2 weeks, and 4 weeks after intervention. After 4 weeks of training, the experimental group showed greater improvement than the control group in all temporospatial gait variables, except for the unaffected step length and step time symmetry which showed no difference. In addition, greater improvements of the affected hip flexor and knee extensor muscle strength were found in the experimental group. In conclusion, a combination of MI with SPCCT provided a greater therapeutic effect on gait and lower limb muscle strengths in stroke survivors.

A structural equation model of falls at home in individuals with chronic stroke, based on the international classification of function, disability, and health

PURPOSE

To use structural equation model (SEM) to explain falls at home in individuals with chronic stroke, based on the International Classification of Functioning, Disability and Health (ICF).

MATERIALS AND METHODS

A cross sectional observation study was conducted in home-dwelling individuals with chronic stroke (N = 236; 148 non-fallers, 88 fallers). Participants were assessed; structural impairments using Modified Ashworth Scale, Fugl-Meyer Assessment upper (FMA-UE), lower (FMA-LE), and sensory function, ankle plantarflexor strength; activity limitations using Timed Up and Go Test, Step Test, Berg Balance Scale, Barthel Index (BI); participation restrictions using Stroke Impact Scale-participation (SIS-P); and contextual factors using home hazard environments, home safety surroundings, risk behaviors, and Fall-related Self Efficacy. The measurement model was analyzed by confirmatory factor analysis. The SEM was conducted to analyze a structural model of falls at home.

RESULTS

FMA-UE was significantly (p<0.01) associated with FMA-LE, combining as one variable in the structural impairments. In the measurement model, variables were fit to their domains, except variables of contextual factors, but the ICF domains did not correspond to disability. A structural model of falls at home demonstrated a significant (p<0.01) direct path of contextual factors and activity limitations with falls at home. The structural impairments showed a significant (p<0.01) direct path with activity limitations. All variables, except BI, SIS-P and risk behaviors, related to their domains in the structural model.

CONCLUSIONS

A structural model of falls at home proposes contextual factors being the strongest association with falls at home that home hazard environments seem the most influence in its domain. The activity limitations presented by balance ability are directed to falls at home. The structural impairments are associated with falls at home through activity limitations. Home assessment to decrease home hazard environments is suggested to prevent falls at home for individuals with chronic stroke.