Paretic propulsion changes with handrail Use in individuals post-stroke.

Background: Roughly 800,000 people experience a stroke every year in the United States, and about 30% of people require walking assistance (walker, cane, etc.) after a stroke. Gait training on a treadmill is a common rehabilitation activity for individuals post-stroke and handrails are typically used to assist with walking during this training, however individual interaction with these handrails are not usually considered and quantitatively reported. Individuals may exert force onto the handrails to aid with propulsive force, but the relationship between limb propulsive force and handrail propulsive force are not known. Research question: How do individuals post-stroke alter paretic propulsive force when using an assistive device, such as handrails on a treadmill? Methods: Twenty-one individuals post-stroke (eight current assistive device users and thirteen individuals who do not use an assistive device) walked on a treadmill for 3 min during three conditions: no handrail use, light handrail use (<5% BW) and self-selected handrail use. Three multilevel models were used to compare percent handrail, paretic and nonparetic propulsion between handrail conditions and assistive device groups. Results: The handrail propulsive impulse was more during the self-selected handrail condition compared to the light handrail condition (p = 0.002). The assistive device use group and the handrail condition fixed effects significantly improved the model fit for paretic propulsive impulse (p = 0.01). The interaction between assistive device use group and handrail condition significantly improved the model fit for nonparetic propulsive impulse (p < 0.001). Significance: These results suggest that handrail use may impact paretic propulsive impulse. Our initial results suggest that if the goal of rehabilitation treadmill training is to increase the paretic propulsive impulse, having the clinician encourage walking with the handrails may be optimal to promote paretic propulsion.

Explicit and implicit locomotor learning in individuals with chronic hemiparetic stroke.

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 computational modeling to determine the individual contributions of explicit and implicit processes 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.

Limitations in utilization and prioritization of standardized somatosensory assessments after stroke: A cross-sectional survey of neurorehabilitation clinicians.

BACKGROUND AND PURPOSE: Somatosensory impairments are common after stroke, but receive limited evaluation and intervention during neurorehabilitation, despite negatively impacting functional movement and recovery. OBJECTIVES: Our objective was to understand the scope of somatosensory assessments used by clinicians in stroke rehabilitation, and barriers to increasing use in clinical practice. METHODS: An electronic survey was distributed to clinicians (physical therapists, occupational therapists, physicians, and nurses) who assessed at least one individual with stroke in the past 6 months. The survey included questions on evaluation procedures, type, and use of somatosensory assessments, as well as barriers and facilitators in clinical practice. RESULTS: Clinicians (N = 431) indicated greater familiarity with non-standardized assessments, and greater utilization compared to standardized assessments (p < 0.0001). Components of tactile sensation were the most commonly assessed modality of somatosensation (25%), while proprioception was rarely assessed (1%). Overall, assessments of motor function were prioritized over assessments of somatosensory function (p < 0.0001). DISCUSSION: Respondents reported assessing somatosensation less frequently than motor function and demonstrated a reliance on rapid and coarse non-standardized assessments that ineffectively capture multi-modal somatosensory impairments, particularly for proprioceptive deficits common post-stroke. In general, clinicians were not familiar with standardized somatosensory assessments, and this knowledge gap likely contributes to lack of translation of these assessments into practice. CONCLUSIONS: Clinicians utilize somatosensory assessments that inadequately capture the multi-modal nature of somatosensory impairments in stroke survivors. Addressing barriers to clinical translation has the potential to increase utilization of standardized assessments to improve the characterization of somatosensory deficits that inform clinical decision-making toward enhancing stroke rehabilitation outcomes.

Characterizing the impact of multiple chronic conditions on return to participation in chronic stroke survivors.

BACKGROUND: Each year, 795,000 Americans experience a stroke. As stroke mortality declines, more individuals are in the chronic phase of recovery (>6 months post-stroke). Over 80% of stroke survivors have multiple, chronic health conditions (MCC). While the relationship between MCC and mortality and function during acute recovery has been explored, less is known about how MCC burden affects participation in chronic stroke survivors. OBJECTIVE: This study investigated whether MCC burden is related to participation in those with chronic stroke. METHODS: Two hundred and sixty-six participants with chronic (≥6 months) stroke were included in this cross-sectional and retrospective analysis. Participants had a mean age of 62.2 ± 12.8 years, and time since stroke (TSS) of 36.0 ± 44.6 months (114F/152 M). Participants completed the 6-minute Walk Test (6MWT), Activities-Specific Balance Confidence Scale (ABC), Modified Cumulative Illness Rating Scale (MCIR) to quantify the presence and severity of chronic illness across 14 body systems, and the Stroke Impact Scale - Participation subscale (SIS-P). Participation (SIS-P) was the dependent variable. Independent variables were entered into a sequential regression model in three blocks: demographic variables, physical capacity (6MWT distance) and balance self-efficacy (ABC), and MCC burden (MCIR). RESULTS: After adjusting for age, sex, and time since stroke, physical capacity and balance self-efficacy explained 31.4% (p < 0.001), and the MCC burden explained 2.0% (p = 0.004). Higher participation was related to lower MCC burden. CONCLUSIONS: MCC burden is a significant contributor to variance in participation in chronic stroke survivors, above and beyond demographics, physical capacity, and self-efficacy, and therefore should be considered when creating rehabilitation programs to improve participation.

Aerobic Exercise Improves Cortical Inhibitory Function After Stroke: A Preliminary Investigation.

BACKGROUND AND PURPOSE: Aerobic exercise can elicit positive effects on neuroplasticity and cognitive executive function but is poorly understood after stroke. We tested the effect of 4 weeks of aerobic exercise training on inhibitory and facilitatory elements of cognitive executive function and electroencephalography markers of cortical inhibition and facilitation. We investigated relationships between stimulus-evoked cortical responses, blood lactate levels during training, and aerobic fitness postintervention. METHODS: Twelve individuals with chronic (>6 months) stroke completed an aerobic exercise intervention (40 minutes, 3×/wk). Electroencephalography and motor response times were assessed during congruent (response facilitation) and incongruent (response inhibition) stimuli of a Flanker task. Aerobic fitness capacity was assessed as o2peak during a treadmill test pre- and postintervention. Blood lactate was assessed acutely (<1 minute) after exercise each week. Cortical inhibition (N2) and facilitation (frontal P3) were quantified as peak amplitudes and latencies of stimulus-evoked electroencephalographic activity over the frontal cortical region. RESULTS: Following exercise training, the response inhibition speed increased while response facilitation remained unchanged. A relationship between earlier cortical N2 response and faster response inhibition emerged postintervention. Individuals who produced higher lactate during exercise training achieved faster response inhibition and tended to show earlier cortical N2 responses postintervention. There were no associations between o2peak and metrics of behavioral or neurophysiologic function. DISCUSSION AND CONCLUSIONS: These preliminary findings provide novel evidence for selective benefits of aerobic exercise on inhibitory control during the initial 4-week period after initiation of exercise training and implicate a potential therapeutic effect of lactate on poststroke inhibitory control.

Moderate to Vigorous Intensity Locomotor Training After Stroke: A Systematic Review and Meta-analysis of Mean Effects and Response Variability.

BACKGROUND AND PURPOSE: This meta-analysis quantified mean effects of moderate to vigorous intensity locomotor training (LT mv ) on walking outcomes in subacute and chronic stroke, and the magnitude of variability in LT mv response. METHODS: Databases were searched for randomized trials comparing LT mv with no intervention, nongait intervention, or low-intensity gait training. Comfortable gait speed (CGS), fastest gait speed (FGS), 6-minute walk test (6MWT), walking activity (steps per day), and adverse effect/event (AE) data were extracted. Pooled estimates were calculated for mean changes, AE relative risks, and the standard deviation of response (SD response ) to LT mv versus control groups, stratified by study chronicity where possible. RESULTS: There were 19 eligible studies (total N = 1096): 14 in chronic stroke (N = 839) and 5 in subacute stroke (N = 257). Compared with control interventions, LT mv yielded significantly greater increases in CGS (chronic, +0.06 m/s [95% confidence interval (CI), 0.01-0.10]; subacute, +0.16 [0.12-0.19]; subacute vs chronic, P = 0.03), FGS (chronic, +0.07 m/s [0.02-0.13]; subacute, +0.21 [0.01, 0.41]; P = 0.04), and 6MWT (chronic, +33 m [24-42]; subacute, +51 [26-77]; P = 0.054) but not steps/day (+260 [-1159 to 1679]). There were no treatment-related serious AEs among 398 LT mv participants in 14 AE-reporting studies. SD response estimates indicated substantial response variability: CGS, 0.11 m/s [0.00-0.15]; FGS, 0.14 m/s [-0.00 to 0.20]; and 6MWT, 41 m [27-51]. DISCUSSION AND CONCLUSIONS: LT mv improves mean walking capacity outcomes in subacute and chronic stroke and does not appear to have high risk of serious harm. Response magnitude varies within and between chronicity subgroups, and few studies have tested effects on daily walking activity or non-serious AEs.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A452 ).

Increasing Activity After Stroke: A Randomized Controlled Trial of High-Intensity Walking and Step Activity Intervention.

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.

ICF classification of therapeutic goals for outpatient episodes of neurorehabilitation in post-stroke and Parkinson disease.

PURPOSE: To understand therapeutic priorities, a secondary data analysis on a retrospective cohort was conducted to classify rehabilitation goals according to the International Classification of Functioning, Disability, and Health (ICF). MATERIALS AND METHODS: Therapeutic goals from an initial outpatient physical or occupational therapy evaluation for patients post-stroke or with Parkinson disease, were classified into Level 1 of the ICF. Goals in the Activity and Participation component were further sub-classified as activity capacity or activity performance (self-report or direct) in daily life. RESULTS: 776 goals across 104 participants were classified into Level 1 of the ICF. The majority, 73% (563/776) were classified as Activity and Participation, 20% (155/776) as Body Function and 2% (17/776) as Environmental Factors. Fifty-two percent (400/776) of all goals were classified as activity capacity and 21% (163/776) as activity performance in daily life, with 21% (160/776) of goals measuring self-report activity performance in daily life and less than 1% (3/776) of goals measuring direct activity performance in daily life. CONCLUSIONS: While the majority of therapeutic goals were classified into the Activity and Participation component, less than 1% of goals measured direct activity performance in daily life. If people seek outpatient rehabilitation to improve functioning in their real-world environment, therapeutic goal setting should reflect this.

The majority of therapeutic goals for an episode of outpatient neurorehabilitation were classified into the Activity and Participation component of the International Classification of Functioning, Disability, and Health.However, less than 1% of therapeutic goals measured direct activity performance in daily life.If people with neurological diagnoses seek out outpatient rehabilitation to improve functioning in their real-world environment, than therapeutic goal setting should reflect this.

Increasing activity after stroke: a randomized controlled trial of highintensity walking and step activity intervention.

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 highintensity walking intervention (FAST), a step activity monitoring behavioral intervention (SAM), or a combined intervention (FAST+SAM) on physical activity (i.e., steps per day). We hypothesized the combined intervention would yield the greatest increase in steps per day. Methods: This assessor-blinded multi-site randomized controlled trial was conducted at four university/hospital-based laboratories. Participants were 21-85 years old, walking without physical assistance following a single, unilateral non-cerebellar 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 for 40 minutes/session at 70-80% heart rate reserve, while SAM received daily feedback and goal-setting of walking activity (steps per day). Assessors and study statistician were masked to group assignment.The a priori-determined primary outcome and primary endpoint was change in steps per day from pre- to post-intervention. Adverse events (AEs) were tracked after randomization. All randomized participants were included in the intent-to-treat analysis.This study is registered at ClinicalTrials.gov, NCT02835313. Findings: Participants were enrolled from July 18, 2016-November 16, 2021. Of 250 randomized participants (mean[SE] age 63[0.80], 116F/134M), 89 were assigned to FAST, 81 to SAM, and 80 to FAST+SAM. Steps per day significantly increased in both the SAM (mean[SE] 1542[267], 95%CI:1014-2069, p<0.001) and FAST+SAM groups (1307[280], 752-1861, p<0.001), but not in the FAST group (406[238], 63-876, p=0.09). There were no deaths or serious study-related AEs and all other minor AEs were similar between groups. Interpretation: 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 per day).

Effects of an Acute High Intensity Exercise Bout on Retention of Explicit, Strategic Locomotor Learning in Individuals With Chronic Stroke.

BACKGROUND: Exercise priming, pairing high intensity exercise with a motor learning task, improves retention of upper extremity tasks in individuals after stroke, but has shown no benefit to locomotor learning. This difference may relate to the type of learning studied. Upper extremity studies used explicit, strategic tasks; locomotor studies used implicit sensorimotor adaptation (split-belt treadmill). Since walking is an important rehabilitation goal, it is crucial to understand under which circumstances exercise priming may improve retention of a newly learned walking pattern. OBJECTIVE: Determine the impact of exercise priming on explicit, strategic locomotor learning task retention in chronic stroke survivors. METHODS: Chronic stroke survivors (>6 months) performed 2 treadmill walking sessions. Visual feedback was used to train increased step length. Participants were assigned to control group (no exercise), continuous exercise (5 minutes high intensity), or long-interval exercise (15 minutes high/moderate intervals). After day 1 learning, participants either rested or performed exercise. On day 2, retention of the learned walking pattern was tested. RESULTS: All groups learned on day 1 (P < .001). The 2 priming groups showed significant changes in blood lactate and heart rate after exercise priming, the resting control group did not (P < .001). On day 2, there was no significant between-group difference in cued or un-cued task retention (P = .963 and .287, respectively). CONCLUSIONS: Exercise priming did not affect retention of an explicit locomotor task in chronic stroke survivors. Further work should explore subgroups of individuals for whom priming may have selective clinical benefit to locomotor learning.ClinicalTrials.gov Identifier: NCT03726047.

Training parameters and longitudinal adaptations that most strongly mediate walking capacity gains from high-intensity interval training post-stroke.

Background: Locomotor high-intensity interval training (HIIT) has been shown to improve walking capacity more than moderate-intensity aerobic training (MAT) after stroke, but it is unclear which training parameter(s) should be prioritized (e.g. speed, heart rate, blood lactate, step count) and to what extent walking capacity gains are the result of neuromotor versus cardiorespiratory adaptations. Objective: Assess which training parameters and longitudinal adaptations most strongly mediate 6-minute walk distance (6MWD) gains from post-stroke HIIT. Methods: The HIT-Stroke Trial randomized 55 persons with chronic stroke and persistent walking limitations to HIIT or MAT and collected detailed training data. Blinded outcomes included 6MWD, plus measures of neuromotor gait function (e.g. fastest 10-meter gait speed) and aerobic capacity (e.g. ventilatory threshold). This ancillary analysis used structural equation models to compare mediating effects of different training parameters and longitudinal adaptations on 6MWD. Results: Net gains in 6MWD from HIIT versus MAT were primarily mediated by faster training speeds and longitudinal adaptations in neuromotor gait function. Training step count was also positively associated with 6MWD gains, but was lower with HIIT versus MAT, which decreased the net 6MWD gain. HIIT generated higher training heart rate and lactate than MAT, but aerobic capacity gains were similar between groups, and 6MWD changes were not associated with training heart rate, training lactate, or aerobic adaptations. Conclusions: To increase walking capacity with post-stroke HIIT, training speed and step count appear to be the most important parameters to prioritize.

Optimal Intensity and Duration of Walking Rehabilitation in Patients With Chronic Stroke: A Randomized Clinical Trial.

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.

Speed-dependent biomechanical changes vary across individual gait metrics post-stroke relative to neurotypical adults.

BACKGROUND: Gait training at fast speeds is recommended to reduce walking activity limitations post-stroke. Fast walking may also reduce gait kinematic impairments post-stroke. However, it is unknown if differences in gait kinematics between people post-stroke and neurotypical adults decrease when walking at faster speeds. OBJECTIVE: To determine the effect of faster walking speeds on gait kinematics post-stroke relative to neurotypical adults walking at similar speeds. METHODS: We performed a secondary analysis with data from 28 people post-stroke and 50 neurotypical adults treadmill walking at multiple speeds. We evaluated the effects of speed and group on individual spatiotemporal and kinematic metrics and performed k-means clustering with all metrics at self-selected and fast speeds. RESULTS: People post-stroke decreased step length asymmetry and trailing limb angle impairment, reducing between-group differences at fast speeds. Speed-dependent changes in peak swing knee flexion, hip hiking, and temporal asymmetries exaggerated between-group differences. Our clustering analyses revealed two clusters. One represented neurotypical gait behavior, composed of neurotypical and post-stroke participants. The other characterized stroke gait behavior-comprised entirely of participants post-stroke with smaller lower extremity Fugl-Meyer scores than the post-stroke participants in the neurotypical gait behavior cluster. Cluster composition was largely consistent at both speeds, and the distance between clusters increased at fast speeds. CONCLUSIONS: The biomechanical effect of fast walking post-stroke varied across individual gait metrics. For participants within the stroke gait behavior cluster, walking faster led to an overall gait pattern more different than neurotypical adults compared to the self-selected speed. This suggests that to potentiate the biomechanical benefits of walking at faster speeds and improve the overall gait pattern post-stroke, gait metrics with smaller speed-dependent changes may need to be specifically targeted within the context of fast walking.

Beyond steps per day: other measures of real-world walking after stroke related to cardiovascular risk.

BACKGROUND: Significant variability exists in how real-world walking has been measured in prior studies in individuals with stroke and it is unknown which measures are most important for cardiovascular risk. It is also unknown whether real-world monitoring is more informative than laboratory-based measures of walking capacity in the context of cardiovascular risk. The purpose of this study was to determine a subset of real-world walking activity measures most strongly associated with systolic blood pressure (SBP), a measure of cardiovascular risk, in people with stroke and if these measures are associated with SBP after accounting for laboratory-based measures of walking capacity. METHODS: This was a cross-sectional analysis of 276 individuals with chronic (≥ 6 months) stroke. Participants wore an activity monitor for ≥ 3 days. Measures of activity volume, activity frequency, activity intensity, and sedentary behavior were calculated. Best subset selection and lasso regression were used to determine which activity measures were most strongly associated with systolic blood pressure. Sequential linear regression was used to determine if these activity measures were associated with systolic blood pressure after accounting for walking capacity (6-Minute Walk Test). RESULTS: Average bout cadence (i.e., the average steps/minute across all bouts of walking) and the number of long (≥ 30 min) sedentary bouts were most strongly associated with systolic blood pressure. After accounting for covariates (ΔR2 = 0.089, p < 0.001) and walking capacity (ΔR2 = 0.002, p = 0.48), these activity measures were significantly associated with systolic blood pressure (ΔR2 = 0.027, p = 0.02). Higher systolic blood pressure was associated with older age (ß = 0.219, p < 0.001), male gender (ß = - 0.121, p = 0.046), black race (ß = 0.165, p = 0.008), and a slower average bout cadence (ß = - 0.159, p = 0.022). CONCLUSIONS: Measures of activity intensity and sedentary behavior may be superior to commonly used measures, such as steps/day, when the outcome of interest is cardiovascular risk. The relationship between walking activity and cardiovascular risk cannot be inferred through laboratory-based assessments of walking capacity.

Split-Belt Adaptation and Savings in People With Parkinson Disease.

BACKGROUND AND PURPOSE: Upper extremity studies suggest that implicit adaptation is less impaired than explicit learning in persons with Parkinson disease (PD). Little work has explored implicit locomotor adaptation and savings in this population, yet implicit locomotor learning is critical for everyday function. This cross-sectional study examined adaptation and savings in individuals with PD during split-belt treadmill walking. METHODS: Fourteen participants completed the following treadmill protocol: Baseline (6 minutes belts tied), Adaptation (10 minutes split), Washout (10 minutes tied), and Readaptation (10 minutes split). Step length and step symmetry index (SSI) were calculated to determine magnitude and rate of adaptation and savings. Rate was calculated as strides to reach SSI plateau during Adaptation and Readaptation. RESULTS: During Early Adaptation and Early Readaptation, SSI was perturbed from Baseline ( P < 0.001 and P = 0.002, respectively). Less perturbation in Early Readaptation ( P < 0.001) demonstrated savings. In Late Adaptation and Late Readaptation, participants returned to Baseline symmetry ( P = 0.026 and P = 0.022, respectively, with adjusted level of significance = 0.007). Adaptation was also seen in reverse asymmetry observed in Early Washout ( P = 0.003 vs Baseline). Readaptation rate was faster than in Adaptation ( P = 0.015), demonstrating savings. DISCUSSION AND CONCLUSIONS: Individuals with PD showed locomotor adaptation in an implicit sensorimotor adaptation task. They also demonstrated savings, with less perturbation and faster adaptation during the second split-belt exposure. However, performance was variable; some individuals showed minimal adaptation. Variations in learning, savings, and clinical presentation highlight the need to further explore characteristics of individuals with PD most likely to benefit from adaptation-based locomotor training.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A395 ).

Relationships Among Environmental Variables, Physical Capacity, Balance Self-Efficacy, and Real-World Walking Activity Post-Stroke.

BACKGROUND: Social and physical environmental factors affect real-world walking activity in individuals with stroke. However, environmental factors are often non-modifiable, presenting a challenge for clinicians working with individuals with stroke whose real-world walking is limited due to environmental barriers. OBJECTIVE: The purpose of this work was to test a model hypothesizing the relationships among environmental factors (specifically, living situation and area deprivation), modifiable factors, and real-world walking activity to understand opportunities for intervention. We hypothesized that balance self-efficacy would mediate the relationship between the environment and real-world walking and that physical capacity would moderate this mediation. METHODS: This was a cross-sectional study of 282 individuals with chronic (≥6 months) stroke. We tested the indirect effect to determine if mediation was present. Multiple group structural equation modeling was used to test if physical capacity moderated this mediation. A χ2 difference test was used to compare the moderation model against the null (no moderation) model. RESULTS: Balance self-efficacy mediated the relationship between area deprivation and real-world walking (indirect effect: ß = -0.04, P = .04). Both the moderation and null models fit the data equally well statistically (χ2(5) = 6.9, P = .23). We therefore accepted the simpler (null) model and concluded that the mediation was not moderated. CONCLUSIONS: Targeting balance self-efficacy may be an effective approach to improving real-world walking in persons with stroke who experience barriers within the physical environment. A stroke survivor's physical capacity may not impact this approach. Future work should consider utilizing more specific measures of the social and physical environment to better understand their influences on real-world walking activity in individuals with stroke. However, the results of this work provide excellent targets for future longitudinal studies targeting real-world walking activity in stroke.

A machine learning approach to identifying important features for achieving step thresholds in individuals with chronic stroke.

BACKGROUND: While many factors are associated with stepping activity after stroke, there is significant variability across studies. One potential reason to explain this variability is that there are certain characteristics that are necessary to achieve greater stepping activity that differ from others that may need to be targeted to improve stepping activity. OBJECTIVE: Using two step thresholds (2500 steps/day, corresponding to home vs. community ambulation and 5500 steps/day, corresponding to achieving physical activity guidelines through walking), we applied 3 different algorithms to determine which predictors are most important to achieve these thresholds. METHODS: We analyzed data from 268 participants with stroke that included 25 demographic, performance-based and self-report variables. Step 1 of our analysis involved dimensionality reduction using lasso regularization. Step 2 applied drop column feature importance to compute the mean importance of each variable. We then assessed which predictors were important to all 3 mathematically unique algorithms. RESULTS: The number of relevant predictors was reduced from 25 to 7 for home vs. community and from 25 to 16 for aerobic thresholds. Drop column feature importance revealed that 6 Minute Walk Test and speed modulation were the only variables found to be important to all 3 algorithms (primary characteristics) for each respective threshold. Other variables related to readiness to change activity behavior and physical health, among others, were found to be important to one or two algorithms (ancillary characteristics). CONCLUSIONS: Addressing physical capacity is necessary but not sufficient to achieve important step thresholds, as ancillary characteristics, such as readiness to change activity behavior and physical health may also need to be targeted. This delineation may explain heterogeneity across studies examining predictors of stepping activity in stroke.

Preliminary Outcomes of Combined Treadmill and Overground High-Intensity Interval Training in Ambulatory Chronic Stroke.

PURPOSE: Locomotor high-intensity interval training (HIIT) is a promising intervention for stroke rehabilitation. However, overground translation of treadmill speed gains has been somewhat limited, some important outcomes have not been tested and baseline response predictors are poorly understood. This pilot study aimed to guide future research by assessing preliminary outcomes of combined overground and treadmill HIIT. MATERIALS AND METHODS: Ten participants >6 months post-stroke were assessed before and after a 4-week no-intervention control phase and a 4-week treatment phase involving 12 sessions of overground and treadmill HIIT. RESULTS: Overground and treadmill gait function both improved during the treatment phase relative to the control phase, with overground speed changes averaging 61% of treadmill speed changes (95% CI: 33-89%). Moderate or larger effect sizes were observed for measures of gait performance, balance, fitness, cognition, fatigue, perceived change and brain volume. Participants with baseline comfortable gait speed <0.4 m/s had less absolute improvement in walking capacity but similar proportional and perceived changes. CONCLUSIONS: These findings reinforce the potential of locomotor HIIT research for stroke rehabilitation and provide guidance for more definitive studies. Based on the current results, future locomotor HIIT studies should consider including: (1) both overground and treadmill training; (2) measures of cognition, fatigue and brain volume, to complement typical motor and fitness assessment; and (3) baseline gait speed as a covariate.