Stroke often causes hemiparesis, affecting balance and walking ability. Propulsion, a major subtask of walking, has two components: trailing limb posture and propulsive force generated by plantarflexor muscles. Our group previously developed a method to challenge propulsion by accelerating the belt supporting the trailing limb during push off. In this study, we test the efficacy of a similar paradigm in 34 post-stroke individuals, and compare the effects of posterior belt accelerations applied to both legs (symmetric condition), and only to the paretic leg (asymmetric condition). We hypothesized that the two conditions would elicit changes in propulsion mechanics during and after exposure. Results indicate that belt accelerations induced measurable effects in paretic propulsion mechanics during exposure, and some of these effects persisted over a 1-3 minute post-exposure session conducted at self-selected speed. Specifically, by the end of the exposure session, participants increased their paretic TLA by $7.2~\pm~0.9$ %, and their plantarflexor muscle activation by $6.6 \pm 2.2$ % in the soleus and $7.8~\pm~2.3$ % in the lateral gastrocnemius, compared to their baseline. Changes in propulsion mechanics led to a small but statistically significant (0.024 m/s or $3.4 \pm 1.4$ %) post-exposure increase in self-selected walking speed. Effects were primarily induced on metrics of propulsion mechanics of the leg directly exposed to belt acceleration; therefore, differential effects as a function of acceleration condition were only observed for the non-paretic leg. A responder analysis indicated that individuals with greater impairment exhibited larger relative changes in plantarflexor muscle activation after exposure.

BACKGROUND:Strategic motor learning, guided by visual feedback (VF), is commonly used in post-stroke gait rehabilitation. While visuospatial working memory (VSWM) has been shown to support VF-guided motor correction in upper limb motor learning tasks, its role in locomotor learning after stroke remains unclear. OBJECTIVE:We examined whether VSWM is related to strategic learning by examining the overall accuracy and improvement in accuracy over time with VF-guided locomotor learning in individuals with chronic stroke. METHODS:Seventy-seven individuals >6 months post-stroke (41 males and 36 females; mean age = 66.3 ± 10.9 years) adapted walking on a split-belt treadmill (2:1 ratio) with real-time VF of step lengths. Feedback was displayed as visual targets on a screen and participants were instructed to use the visual cues to counteract the split-belt perturbation and restore their pre-perturbation step lengths. Strategic learning was assessed using 2 outcomes: overall accuracy and improvement in accuracy over strides during the VF phase. VSWM was assessed with the Spatial Addition subtest of the Wechsler Memory Scale-IV. RESULTS:After adjusting for age, sex, time since stroke, and lower extremity Fugl-Meyer score, VSWM explained a significant proportion of the variance in both outcomes (overall accuracy: ΔR2 = .085, P = .013; improvement in accuracy: ΔR2 = .153, P < .001). CONCLUSION:Our findings suggest that VSWM may be important for strategic locomotor learning with VF in people with chronic stroke, highlighting its potential relevance as a key consideration in designing walking rehabilitation strategies for people after stroke.

Objective To understand in people with stroke: (1) reasons for cardiopulmonary treadmill exercise test termination, (2) how frequently secondary criteria indicating a maximal test are met, and (3) how test termination is related to volume of oxygen consumption and participant characteristics. Design A secondary analysis from the Promoting Recovery Optimization of Walking Activity in Stroke (NCT02835313) clinical trial. Setting Four outpatient rehabilitation clinics. Participants People with chronic stroke able to walk without assistance of another person. Intervention Participants ( n = 250) randomized in a larger clinical trial completed symptom limited graded exercise treadmill tests pre- ( n = 247) and post-intervention ( n = 185). Treadmill exercise tests were conducted at constant speed with incremental incline increases. Main Measures The primary measure was reason for cardiopulmonary exercise test termination. Secondary measures included: oxygen consumption, ventilatory threshold, peak heart rate, respiratory exchange ratio, six-minute walk test, and fastest walking speed. Results There were six categories of test termination, electrocardiogram (11%), blood pressure/heart rate (13%), biomechanical (25%), self-selected (41%), equipment malfunction (8%), and other (2%). Only 1.9% of tests achieved the threshold to confirm a maximal aerobic effort. There were no differences in peak volume of oxygen consumption or participant characteristics between test termination categories. Conclusions Analyses indicate few with chronic stroke exhibit a maximal aerobic effort on a cardiopulmonary exercise test. If the cardiorespiratory system is not thoroughly taxed during treadmill exercise tests in people with chronic stroke, interpreting results as their cardiorespiratory fitness should be done cautiously.

BackgroundIndividuals with chronic stroke are less active, which is both a consequence of stroke-related impairments and a risk factor for future health complications. The PROWALKS clinical trial found significant gains in real-world walking activity (steps/day) after 12 weeks of a step activity monitoring behavioral intervention, provided either alone (SAM) or with high-intensity gait training (FAST + SAM), but not after high-intensity gait training alone (FAST). Previous research in individuals after stroke suggests that tailored behavioral counseling may lead to better long-term physical activity participation, but no previous work has focused on post-intervention maintenance of walking activity changes.ObjectiveTo investigate whether steps/day changes after training (POST) were maintained at 6 months (6MO) and 12 months (12MO) after baseline. We hypothesized that SAM and FAST + SAM groups would have better maintenance of steps/day changes than the FAST group. Methods. This analysis included all participants who completed the PROWALKS intervention (n = 200, mean[SD] age: 63.27[12.41], 102 male/98 female, >6 months post-stroke). Analysis outcomes were steps/day change from POST-6MO, and from POST-12MO.ResultsAll groups significantly decreased in steps/day from POST-6MO (P = .001, FAST decreased by mean[SE] 160[272], SAM by 1016[270], FAST + SAM by 400[300]), and POST-12MO (P < .001, FAST decreased by 610[280], SAM by 1072[306], FAST + SAM by 568[313]). There were no significant differences between groups.ConclusionsAll intervention groups showed significant declines in steps/day between POST and 6MO and between POST and 12MO. These results add to a growing body of literature suggesting that a behavioral intervention to initiate behavior change may not be sufficient for maintenance of change.Registration:This study is registered at ClinicalTrials.gov, NCT02835313.

Background:Current practice guidelines recommend moderate to vigorous intensity locomotor training to improve walking outcomes in chronic stroke. However, these intensities span a wide range, and the lack of specificity may lead to under-dosing or over-dosing of training intensity. Recent evidence indicates that vigorous intensity locomotor training improves walking outcomes significantly more than moderate intensity. Although, previous studies have not been powered to rule out the possibility of meaningful risk increases or negligible benefit with vigorous versus moderate intensity, nor have they been designed to compare sustained effects after training ends. In addition, small subgroup analyses have suggested that individuals with severe walking limitations (speed <0.4 m/s) may require vigorous training intensity to have meaningful benefit, but this has not been prospectively tested with a sufficient sample. The results of this study are expected to provide more specific guidance for optimizing locomotor training intensity and walking outcomes in chronic stroke. Methods:In this single-blind, 3-site, randomized trial, 156 chronic (>6 months) stroke survivors will be allocated to 36 sessions (3 times a week for 12 weeks) of either high intensity interval or moderate intensity continuous locomotor training. Eligible participants have residual walking limitations from stroke and can walk without continuous physical assistance from another person. At least 52 participants will have severe baseline walking speed limitations. Outcomes are assessed at baseline, after 4 weeks, 8 weeks, 12 weeks (POST), and 3 months after completing training. The primary outcome is walking capacity (6-minute walk distance). Secondary outcomes include comfortable and fast gait speed, aerobic capacity, fatigue, balance confidence, quality of life, and motivation for exercise. Statistical analyses will compare outcome changes and adverse events between treatment groups, and will include subgrouping by walking limitation severity. Discussion:This study will provide important new information to guide greater specificity and individualization of locomotor training intensity in chronic stroke. Trial Registration:ClinicalTrials.gov NCT06268041 ; Registration Date: 2024-02-12.

Motor learning involves both explicit and implicit processes that are fundamental for acquiring and adapting complex motor skills. However, stroke may damage the neural substrates underlying explicit and/or implicit learning, leading to deficits in overall motor performance. While both learning processes are typically used in concert in daily life and rehabilitation, no gait studies have determined how these processes function together after stroke when tested during a task that elicits dissociable contributions from both. Here, we compared explicit and implicit locomotor learning in individuals with chronic stroke to age- and sex-matched neurologically intact controls. We assessed implicit learning using split-belt adaptation (where two treadmill belts move at different speeds). We assessed explicit learning (i.e., strategy-use) using visual feedback during split-belt walking to help individuals explicitly correct for step length errors created by the split-belts. The removal of visual feedback after the first 40 strides of split-belt walking, combined with task instructions, minimized contributions from explicit learning for the remainder of the task. We utilized a multi-rate state-space model to characterize individual explicit and implicit process contributions to overall behavioral change. The computational and behavioral analyses revealed that, compared to controls, individuals with chronic stroke demonstrated deficits in both explicit and implicit contributions to locomotor learning, a result that runs counter to prior work testing each process individually during gait. Since post-stroke locomotor rehabilitation involves interventions that rely on both explicit and implicit motor learning, future work should determine how locomotor rehabilitation interventions can be structured to optimize overall motor learning.

BACKGROUND: Physical inactivity in people with chronic stroke profoundly affects daily function and increases recurrent stroke risk and mortality, making physical activity improvements an important target of intervention. We compared the effects of a high-intensity walking intervention (FAST), a step activity monitoring behavioral intervention (SAM), or a combined intervention (FAST+SAM) on physical activity (ie, steps/day). We hypothesized the combined intervention would yield the greatest increase in steps/day. METHODS: This assessor-blinded multisite randomized controlled trial was conducted at 4 university/hospital-based laboratories. Participants were 21 to 85 years old, walking without physical assistance following a single, unilateral noncerebellar stroke of ≥6 months duration, and randomly assigned to FAST, SAM, or FAST+SAM for 12 weeks (2–3 sessions/week). FAST training consisted of walking-related activities at 70% to 80% heart rate reserve, while SAM received daily feedback and goal setting of walking activity (steps/day). Assessors and study statistician were masked to group assignment. The a priori–determined primary outcome and end point was a comparison of the change in steps/day between the 3 intervention groups from pre- to post-intervention. Adverse events were tracked after randomization. All randomized participants were included in the intent-to-treat analysis. RESULTS: Participants were enrolled from July 18, 2016, to November 16, 2021. Of 2385 participants initially screened, 250 participants were randomized (mean [SE] age, 63 [0.80] years; 116 females/134 males), with 89 assigned to FAST, 81 to SAM, and 80 to FAST+SAM. Steps/day significantly increased in both the SAM (mean [SE], 1542 [267; 95% CI, 1014–2069] P <0.001) and FAST+SAM group (1307 [280; 95% CI, 752–1861] P <0.001) but not in the FAST group (406 [238; 95% CI, −63 to 876] P =0.09). There were no deaths or serious study-related adverse events. CONCLUSIONS: Only individuals with chronic stroke who completed a step activity monitoring behavioral intervention with skilled coaching and goal progression demonstrated improvements in physical activity (steps/day). REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02835313.

Peak oxygen consumption (VO2 peak), measured through cardiopulmonary exercise testing (CPET), is considered the gold standard to quantify a person’s cardiorespiratory fitness (CRF). CPET tests the multifaceted way in which the cardiorespiratory (CR), metabolic, musculoskeletal, and neurological systems interact to deliver and utilize oxygen during increased workloads. As studies of high intensity exercise in people with chronic stroke (PwS; > 6 months) have grown, CPET has been used to measure CRF in this population. PwS have VO2 peak values 53% of those found in age- and sex-matched controls, which likely plays a role in the presence of diminished mobility. Given significant neuromotor deficits experienced by PwS, peak performance may be impacted by neuromuscular factors. If the CR system is not the main limiting factor in CPET in PwS, the VO2 peak obtained may not accurately represent their CRF. PURPOSE: To characterize cardiorespiratory and metabolic responses to CPET in PwS. METHODS: PwS were included if their walking speed was 0.3-1.0 m/s and they walked <8000 steps/day. Participants underwent a maximal treadmill CPET with a 12-lead electrocardiogram and breath-by-breath analysis of oxygen consumption recording continuously. Treadmill speed was constant at 85% of the individual’s maximal treadmill speed. Participants first walked at 0% incline for 2 minutes, next at a 2% incline for 2 minutes, and then the incline increased by 2% each minute. Tests were terminated if biomechanical faults prevented participants from walking safely or per ACSM guidelines. RESULTS: 307 participants with chronic stroke (> 6 months; age (y) 63.1 + 12.7; 45.8% female, 40.6% on beta-blocker medication, BMI 30.5 + 6.3) completed a baseline CPET as part of a larger, multi-site randomized clinical trial (PROWALKS). Participants had an average resting VO2 of 2.7 + 0.96 mL/kg/min and VO2 peak of 11.8 + 5.2 mL/kg/min. Total exercise time was 4.9 + 2.7 minutes with a HRpeak of 125.8 + 21.4 beats/min (76% of age predicted HRmax) and RERpeak of 0.99 + 0.13. CPETs were ended for multiple reasons: a) self-selected stop (39.4%); b) clinician stopped due to BP or ECG (31.3%), or c) biomechanical faults (29.3%). CONCLUSION: Results suggest PwS rarely achieve ACSM criteria for a maximal test, indicating CPET results in PwS may not represent a true test of CRF.

Importance For walking rehabilitation after stroke, training intensity and duration are critical dosing parameters that lack optimization. Objective To assess the optimal training intensity (vigorous vs moderate) and minimum training duration (4, 8, or 12 weeks) needed to maximize immediate improvement in walking capacity in patients with chronic stroke. Design, Setting, and Participants This multicenter randomized clinical trial using an intent-to-treat analysis was conducted from January 2019 to April 2022 at rehabilitation and exercise research laboratories. Survivors of a single stroke who were aged 40 to 80 years and had persistent walking limitations 6 months or more after the stroke were enrolled. Interventions Participants were randomized 1:1 to high-intensity interval training (HIIT) or moderate-intensity aerobic training (MAT), each involving 45 minutes of walking practice 3 times per week for 12 weeks. The HIIT protocol used repeated 30-second bursts of walking at maximum safe speed, alternated with 30- to 60-second rest periods, targeting a mean aerobic intensity above 60% of the heart rate reserve (HRR). The MAT protocol used continuous walking with speed adjusted to maintain an initial target of 40% of the HRR, progressing up to 60% of the HRR as tolerated. Main Outcomes and Measures The main outcome was 6-minute walk test distance. Outcomes were assessed by blinded raters after 4, 8, and 12 weeks of training. Results Of 55 participants (mean [SD] age, 63 [10] years; 36 male [65.5%]), 27 were randomized to HIIT and 28 to MAT. The mean (SD) time since stroke was 2.5 (1.3) years, and mean (SD) 6-minute walk test distance at baseline was 239 (132) m. Participants attended 1675 of 1980 planned treatment visits (84.6%) and 197 of 220 planned testing visits (89.5%). No serious adverse events related to study procedures occurred. Groups had similar 6-minute walk test distance changes after 4 weeks (HIIT, 27 m [95% CI, 6-48 m]; MAT, 12 m [95% CI, -9 to 33 m]; mean difference, 15 m [95% CI, -13 to 42 m]; P = .28), but HIIT elicited greater gains after 8 weeks (58 m [95% CI, 39-76 m] vs 29 m [95% CI, 9-48 m]; mean difference, 29 m [95% CI, 5-54 m]; P = .02) and 12 weeks (71 m [95% CI, 49-94 m] vs 27 m [95% CI, 3-50 m]; mean difference, 44 m [95% CI, 14-74 m]; P = .005) of training; HIIT also showed greater improvements than MAT on some secondary measures of gait speed and fatigue. Conclusions and Relevance These findings show proof of concept that vigorous training intensity is a critical dosing parameter for walking rehabilitation. In patients with chronic stroke, vigorous walking exercise produced significant and meaningful gains in walking capacity with only 4 weeks of training, but at least 12 weeks were needed to maximize immediate gains. Trial Registration ClinicalTrials.gov Identifier: NCT03760016.

ABSTRACT Introduction For walking rehabilitation after stroke, training intensity and duration are critical dosing parameters that lack optimization. This trial aimed to determine the optimal training intensity (vigorous vs moderate) and minimum training duration (4, 8 or 12 weeks) needed to maximize immediate improvement in walking capacity in chronic stroke. Methods Persons with chronic post-stroke gait dysfunction at three centers were randomized to high-intensity interval training (HIT) or moderate intensity aerobic training (MAT), each involving 45 minutes of treadmill and overground walking exercise with a physical therapist, 3 times per week for 12 weeks. The HIT protocol used repeated 30 second bursts of walking at maximum safe speed, alternated with 30-60 second recovery periods, targeting an average aerobic intensity above 60% heart rate reserve (HRR). The MAT protocol used continuous walking with speed adjusted to maintain an initial target of 40 ± 5% HRR, progressing by 5% HRR every 2 weeks, up to 60% HRR as tolerated. Blinded assessment at baseline and after 4, 8 and 12 weeks of training included the 6-minute walk test (6MWT) as the primary measure of walking capacity. Results Randomized participants (N=55) attended 1,675 (85%) of 1,980 planned treatment sessions and 197 (90%) of 220 planned testing sessions. No serious adverse events related to study procedures occurred. Compared with MAT, HIT involved significantly higher training speeds (161% vs 96% baseline fastest 10-meter speed, p<0.0001) and mean aerobic intensity (61% vs 46% HRR, p<0.0001) across treatment visits. There was no significant between-group difference in 6MWT changes after 4 weeks of training (HIT +27 meters [95% CI: 6-48], MAT +12 meters [-9-33], p=0.28), but randomization to HIT resulted in significantly greater gains than MAT after 8 weeks (+58 [39-76] vs +29 [9-48] meters, p=0.02) and 12 weeks (+71 [49-94] vs +27 [3-50] meters, p=0.005) of training. HIT also showed significantly greater improvements than MAT on some measures of gait speed, fatigue and exercise capacity. Discussion These findings show proof of concept that vigorous training intensity is a critical dosing parameter for walking rehabilitation. In chronic stroke, vigorous walking exercise can produce significant and meaningful gains in walking capacity with only 4 weeks of training, but at least 12 weeks are needed to maximize immediate gains.

Supplemental Digital Content is Available in the Text. Background and Purpose: The transtheoretical model is a health behavior model used to understand an individual's readiness to change their behavior. This study aims to apply the transtheoretical model in understanding a person with stroke's readiness to change their activity level, as it relates to physical capacity, physical health, depressive symptoms, self-efficacy, and daily stepping activity. Methods: This was a cross-sectional analysis of baseline data from a clinical trial. Participants' readiness to change their activity levels was measured via self-report and daily stepping activity was measured using a step activity monitor. Robust regression (M-estimation with robust standard errors) was used to test the relationship between readiness to change and measures of physical capacity (6-minute walk test, self-selected walking speed), physical health (body mass index, age-adjusted Charlson Comorbidity Index), depressive symptoms (Patient Health Questionnaire-9), self-efficacy (Activities-Specific Balance Confidence Scale), and daily stepping (steps per day). Results: A total of 274 individuals were included in the analysis. Adjusted for age, readiness to change was positively related to daily stepping (β = 0.29, P < 0.001) and negatively related to depressive symptoms (β = −0.13, P = 0.01). Readiness to change was not significantly associated with measures of physical capacity, physical health, or self-efficacy. Discussion: These results suggest that individuals with stroke in the later stages of change may demonstrate greater daily stepping activity and lower depressive symptoms compared with those in earlier stages. Conclusions: Understanding the relationship between readiness to change, daily stepping, and depressive symptoms will help clinicians implement appropriate stage-specific intervention strategies and facilitate greater improvement in activity levels. Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A333).

Background: Standing postural sway is often quantified from center of pressure trajectories. During assessments of longer durations, children may fidget, thus limiting the feasibility and validity of sway recordings. Research question: Do postural sway sample durations less than 30 s maintain construct and concurrent validity? Methods: In this case-control, observational study, we measured postural sway in 41 children (age 5-12 years, 23 typically developing (TD); 18 with spastic cerebral palsy (CP), 13 diplegic and 5 hemiplegic, 11 GMFCS level I and 7 level II) for 30-second eyes-opened and eyes-closed conditions. From a single recording, 5-second incremental durations of 5 30 s were considered in this analysis. We quantified anteroposterior, mediolateral, and transverse-plane sway using seven time-domain variables: root-mean-square error, total excursion, mean frequency, mean distance, sway area, and 95 % confidence circle and ellipse areas. Variables were calculated in eyes-opened and eyes-closed conditions, as well as the ratio of the two. Construct validity was evaluated by the persistence of large effect sizes (Glass's Delta >= 0.80) between CP and TD participants at shorter durations than 30 s. Concurrent validity was evaluated by the correlations of shorter duration measures to the 30 s measure. Results: Seven sway measures had large between-group effects (Glass's Delta >= 1.02) for the 30 s measure that persisted (Glass's Delta >= 0.81) at shorter durations (5 - 25 s) and also maintained concurrent validity (r >= 0.83). Six of these seven measures were taken in the eyes-closed condition, and all seven measures were in the mediolateral direction or transverse plane. Significance: Our analysis suggests that sway durations less than 30 s can uphold construct and concurrent validity. These measures were primarily in the eyes-closed conditions and mediolateral direction. These results are a promising indicator that shorter-duration sway measures may be of utility when fidgeting prevents longer recordings.

Recumbent stationary cycling is a potential exercise modality for individuals with cerebral palsy (CP) that lack the postural control needed for upright exercises. Functional electrical stimulation (FES) of lower extremity muscles can help such individuals reach the cycling intensities that are required for aerobic benefits. The aim of this study was to examine the effect of cycling with and without FES assistance to that of a no-intervention control group on the cardiorespiratory fitness of children with CP. Thirty-nine participants were randomized to a FES group that underwent an 8-week FES-assisted cycling program, the volitional group (VOL), who cycled without FES, or a no-intervention control group (CON) (15 FES, 11 VOL, 13 CON). Cadence, peak VO2, and net rise in heart rate were assessed at baseline, end of training, and washout (8-weeks after cessation of training). Latent growth curve modeling was used for analysis. The FES group showed significantly higher cycling cadences than the VOL and CON groups at POST and WO. There were no differences in improvements in the peak VO2 and peak net HR between groups. FES-assisted cycling may help children with CP attain higher cycling cadences and to retain these gains after training cessation. Higher training intensities may be necessary to obtain improvements in peak VO2 and heart rate.

Abstract Background Stroke results in neurologic impairments and aerobic deconditioning that contribute to limited walking capacity which is a major barrier post-stroke. Current exercise recommendations and stroke rehabilitation guidelines recommend moderate-intensity aerobic training post-stroke. Locomotor high-intensity interval training is a promising new strategy that has shown significantly greater improvements in aerobic fitness and motor performance than moderate-intensity aerobic training in other populations. However, the relative benefits and risks of high-intensity interval training and moderate-intensity aerobic training remain poorly understood following stroke. In this study, we hypothesize that locomotor high-intensity interval training will result in greater improvements in walking capacity than moderate-intensity aerobic training. Methods Using a single-blind, 3-site randomized controlled trial, 50 chronic (> 6 months) stroke survivors are randomly assigned to complete 36 locomotor training sessions of either high-intensity interval training or moderate-intensity aerobic training. Main eligibility criteria are age 40–80 years, single stroke for which the participant received treatment (experienced 6 months to 5 years prior to consent), walking speed ≤ 1.0 m/s, able to walk at least 3 min on the treadmill at ≥ 0.13 m/s (0.3 mph), stable cardiovascular condition (American Heart Association class B), and the ability to walk 10 m overground without continuous physical assistance. The primary outcome (walking capacity) and secondary outcomes (self-selected and fast gait speed, aerobic fitness, and fatigue) are assessed prior to initiating training and after 4 weeks, 8 weeks, and 12 weeks of training. Discussion This study will provide fundamental new knowledge to inform the selection of intensity and duration dosing parameters for gait recovery and optimization of aerobic training interventions in chronic stroke. Data needed to justify and design a subsequent definitive trial will also be obtained. Thus, the results of this study will inform future stroke rehabilitation guidelines on how to optimally improve walking capacity following stroke. Trial registration ClinicalTrials.gov NCT03760016 . Registered on November 30, 2018.

Cerebral palsy is a neurodevelopmental movement disorder that affects coordination and balance. Therapeutic treatments for balance deficiencies in this population primarily focus on the musculoskeletal system, whereas the neural basis of balance impairment is often overlooked. Magnetic resonance elastography (MRE) is an emerging technique that has the ability to sensitively assess microstructural brain health through in vivo measurements of neural tissue stiffness. Using magnetic resonance elastography, we have previously measured significantly softer grey matter in children with cerebral palsy as compared with typically developing children. To further allow magnetic resonance elastography to be a clinically useful tool in rehabilitation, we aim to understand how brain stiffness in children with cerebral palsy is related to dynamic balance reaction performance as measured through anterior and posterior single-stepping thresholds, defined as the standing perturbation magnitudes that elicit anterior or posterior recovery steps. We found that global brain stiffness is significantly correlated with posterior stepping thresholds ( P = .024) such that higher brain stiffness was related to better balance recovery. We further identified specific regions of the brain where stiffness was correlated with stepping thresholds, including the precentral and postcentral gyri, the precuneus and cuneus, and the superior temporal gyrus. Identifying brain regions affected in cerebral palsy and related to balance impairment can help inform rehabilitation strategies targeting neuroplasticity to improve motor function.

Aim To compare anterior and posterior standing balance reactions, as measured by single-stepping thresholds, in children with and without spastic cerebral palsy (CP). Method Seventeen ambulatory children with spastic CP (eight males, nine females) and 28 typically developing children (13 males, 15 females; age range 5-12y, mean [SD] 9y 2mo [2y 3mo]), were included in this cross-sectional, observational study. Balance reaction skill was quantified as anterior and posterior single-stepping thresholds, or the treadmill-induced perturbations that consistently elicited a step in that direction. In order to understand the underlying mechanisms of between-group differences in stepping thresholds, dynamic stability was quantified using the minimum margin of stability. Ankle muscle activation latency, magnitude, and co-contraction were assessed with surface electromyography. Results We observed an age and group interaction for anterior thresholds (p=0.001, partial eta(2)=0.24). At older (approximate to 11y; p<0.001, partial eta(2)=0.48), but not younger (approximate to 7y; p=0.33, partial eta(2)=0.02) ages, typically developing children had larger anterior thresholds than those with CP. In response to near-threshold anterior perturbations, older typically developing children recovered from more instability than their peers with CP (p=0.004, partial eta(2)=0.18). Older children had no between-group differences in ankle muscle activity. No between-group differences were observed in posterior thresholds. Interpretation The effects of CP on balance reactions are age- and direction-specific. Older typically developing children are more able or willing to withhold a step when unstable.

Video- and sensor-based gait analysis systems are rapidly emerging for use in ‘real world’ scenarios outside of typical instrumented motion analysis laboratories. Unlike laboratory systems, such systems do not use kinetic data from force plates, rather, gait events such as initial contact (IC) and terminal contact (TC) are estimated from video and sensor signals. There are, however, detection errors inherent in kinematic gait event detection methods (GEDM) and comparative study between classic laboratory and video/sensor-based systems is warranted. For this study, three kinematic methods: coordinate based treadmill algorithm (CBTA), shank angular velocity (SK), and foot velocity algorithm (FVA) were compared to ‘gold standard’ force plate methods (GS) for determining IC and TC in adults (n = 6), typically developing children (n = 5) and children with cerebral palsy (n = 6). The root mean square error (RMSE) values for CBTA, SK, and FVA were 27.22, 47.33, and 78.41 ms, respectively. On average, GED was detected earlier in CBTA and SK (CBTA: −9.54 ± 0.66 ms, SK: −33.41 ± 0.86 ms) and delayed in FVA (21.00 ± 1.96 ms). The statistical model demonstrated insensitivity to variations in group, side, and individuals. Out of three kinematic GEDMs, SK GEDM can best be used for sensor-based gait event detection.

Functional electrical stimulation systems are used as neuroprosthetic devices in rehabilitative interventions such as gait training. Stimulator triggers, implemented to control stimulation delivery, range from open- to closed-loop controllers. Finite-state controllers trigger stimulators when specific conditions are met and utilize preset sequences of stimulation. Wearable sensors provide the necessary input to differentiate gait phases during walking and trigger stimulation. However, gait phase detection is associated with inherent system delays. In this study, five stimulator triggers designed to compensate for gait phase detection delays were tested to determine which trigger most accurately delivered stimulation at the desired times of the gait cycle. Motion capture data were collected on seven typically-developing children while walking on an instrumented treadmill. Participants wore one inertial measurement unit on each ankle and gyroscope data were streamed into the gait phase detection algorithm. Five triggers, based on gait phase detection, were used to simulate stimulation to five muscle groups, bilaterally. For each condition, stimulation signals were collected in the motion capture software via analog channels and compared to the desired timing determined by kinematic and kinetic data. Results illustrate that gait phase detection is a viable finite-state control, and appropriate system delay compensations, on average, reduce stimulation delivery delays by 6.7% of the gait cycle.

A recently designed gait phase detection (GPD) system, with the ability to detect all seven phases of gait in healthy adults, was modified for GPD in children with cerebral palsy (CP). A shank-attached gyroscope sent angular velocity to a rule-based algorithm in LabVIEW to identify the distinct characteristics of the signal. Seven typically developing children (TD) and five children with CP were asked to walk on treadmill at their self-selected speed while using this system. Using only shank angular velocity, all seven phases of gait (Loading Response, Mid-Stance, Terminal Stance, Pre-Swing, Initial Swing, Mid-Swing and Terminal Swing) were reliably detected in real time. System performance was validated against two established GPD methods: (1) force-sensing resistors (GPD-FSR) (for typically developing children) and (2) motion capture (GPD-MoCap) (for both typically developing children and children with CP). The system detected over 99% of the phases identified by GPD-FSR and GPD-MoCap. Absolute values of average gait phase onset detection deviations relative to GPD-MoCap were less than 100 ms for both TD children and children with CP. The newly designed system, with minimized sensor setup and low processing burden, is cosmetic and economical, making it a viable solution for real-time stand-alone and portable applications such as triggering functional electrical stimulation (FES) in rehabilitation systems. This paper verifies the applicability of the GPD system to identify specific gait events for triggering FES to enhance gait in children with CP.