Evaluating the Neural Underpinnings of Motivation for Walking Exercise

OBJECTIVE

Motivation is critically important for rehabilitation, exercise, and motor performance, but its neural basis is poorly understood. Recent correlational research suggests that the dorsomedial prefrontal cortex (dmPFC) may be involved in motivation for walking activity and/or descending motor output. This study experimentally evaluated brain activity changes in periods of additional motivation during walking exercise and tested how these brain activity changes relate to self-reported exercise motivation and walking speed.

METHODS

Adults without disability (N = 26; 65% women; 25 [standard deviation = 5] years old) performed a vigorous exercise experiment involving 20 trials of maximal speed overground walking. Half of the trials were randomized to include "extra-motivation" stimuli (lap timer, tracked best lap time, and verbal encouragement). Wearable near-infrared spectroscopy measured oxygenated hemoglobin responses from frontal lobe regions, including the dmPFC, primary sensorimotor, dorsolateral prefrontal, anterior prefrontal, supplementary motor, and dorsal premotor cortices.

RESULTS

Compared with standard trials, participants walked faster during extra-motivation trials (2.43 vs 2.67 m/s; P < .0001) and had higher oxygenated hemoglobin responses in all tested brain regions, including dmPFC (+842 vs +1694 μM; P < .0001). Greater dmPFC activity was correlated with more self-determined motivation for exercise between individuals (r = 0.55; P = .004) and faster walking speed between trials (r = 0.18; P = .0002). dmPFC was the only tested brain region that showed both of these associations.

CONCLUSION

Simple motivational stimuli during walking exercise seem to upregulate widespread brain regions. Results suggest that dmPFC may be a key brain region linking affective signaling to motor output.

IMPACT

These findings provide a potential biologic basis for the benefits of motivational stimuli, elicited with clinically feasible methods during walking exercise. Future clinical studies could build on this information to develop prognostic biomarkers and test novel brain stimulation targets for enhancing exercise motivation (eg, dmPFC).

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 ).

Motivation-related influences on fNIRS signals during walking exercise: a permutation entropy approach

Cortical activity is typically indexed by analyzing functional near-infrared spectroscopy (fNIRS) signals in terms of the mean (e.g., mean oxygenated hemoglobin; HbO). Entropy approaches have been proposed as useful complementary methods for analyzing fNIRS signals. Entropy methods consider the regularity of a time series, and in doing so, may provide additional insights into the underlying dynamics of brain activity. Recent research using fNIRS found that non-disabled adults exhibit widespread increases in cortical activity and walk faster when under "extra motivation" conditions (e.g., verbal encouragement, lap timer) compared to trials without such motivators ("standard motivation"). This ancillary analysis of that study aimed to assess the extent to which fNIRS permutation entropy (PE) was affected by motivational conditions and explained variance in self-reported motivation. No regional PE differences were found between different motivational conditions. However, a greater difference in PE between motivational conditions (higher in standard, lower in extra motivation) in the anterior prefrontal cortex (aPFC) was associated with greater self-determined motivation. PE was also higher (less regular) in the primary sensorimotor cortex lower limb area compared to all other cortical areas analyzed, except the dorsal premotor cortex, regardless of motivational condition. This study provides early evidence to suggest that while different motivational environments during walking activity influence the magnitude of fNIRS signals, they may not influence the regularity of cortical signals. However, the magnitude of PE difference between motivational conditions was related to self-determined motivation in the aPFC, and this is an area warranting further investigation.

Insufficiencies in sensory systems reweighting is associated with walking impairment severity in chronic stroke: an observational cohort study

Background

Walking and balance impairment are common sequelae of stroke and significantly impact functional independence, morbidity, and mortality. Adequate postural stability is needed for walking, which requires sufficient integration of sensory information between the visual, somatosensory, and vestibular centers. "Sensory reweighting" describes the normal physiologic response needed to maintain postural stability in the absence of sufficient visual or somatosensory information and is believed to play a critical role in preserving postural stability after stroke. However, the extent to which sensory reweighting successfully maintains postural stability in the chronic stages of stroke and its potential impact on walking function remains understudied.

Methods

In this cross-sectional study, fifty-eight community-dwelling ambulatory chronic stroke survivors underwent baseline postural stability testing during quiet stance using the modified Clinical test of Sensory Interaction in Balance (mCTSIB) and assessment of spatiotemporal gait parameters.

Results

Seventy-six percent (45/58) of participants showed sufficient sensory reweighting with visual and somatosensory deprivation for maintaining postural stability, albeit with greater postural sway velocity indices than normative data. In contrast, survivors with insufficient reweighting demonstrated markedly slower overground walking speeds, greater spatiotemporal asymmetry, and limited acceleration potential.

Conclusion

Adequate sensory system reweighting is essential for chronic stroke survivors' postural stability and walking independence. Greater emphasis should be placed on rehabilitation strategies incorporating multisensory system integration testing and strengthening as part of walking rehabilitation protocols. Given its potential impact on outcomes, walking rehabilitation trials may benefit from incorporating formal postural stability testing in design and group stratification.

A 3-minute recumbent stepper test in chronic stroke

BACKGROUND

Persons with stroke often have difficulty achieving target heart rate (HR) during graded exercise testing (GXT), which is known to limit test sensitivity for detecting clinically relevant cardiac conditions. A novel Recumbent Stepper 3-minute (RS 3Min) "all out" test may increase sensitivity of stress testing after stroke.

OBJECTIVE

To determine the feasibility of adding the RS 3Min test after GXT among persons after stroke.

DESIGN

A within-participant, nonrandomized, repeated measures design.

SETTING

Rehabilitation research laboratory and cardiovascular stress laboratory PARTICIPANTS: Fifteen participants with chronic stroke (56.7 ± 9.6 years; 6.4 ± 4.3 years post stroke; 8 male).

INTERVENTIONS

All participants randomly completed (1) a symptom-limited treadmill GXT and (2) a symptom-limited RS GXT followed by RS 3Min critical power test.

MAIN OUTCOME MEASURES

HR, ratings of perceived exertion, oxygen consumption, respiratory exchange ratio, and power output measured continuously during each test. Blood pressure measured every 2 minutes and or immediately post exercise. P value set at p < .05 from omnibus test for a significant difference among protocols.

RESULTS

The RS 3Min test had a significantly higher rate of achieving target HR compared to the RS GXT (9/14 vs 4/14, p = .02) and was not significantly different from the treadmill GXT (9/14 vs 5/14, p = .09). Minimum power output during the RS 3Min was significantly higher than peak power output during the RS GXT (110 ± 41 W vs. 84 ± 22 W, p = .02) with 12/15 participants reaching a VO2 plateau.

CONCLUSIONS

Although additional studies with randomized designs are needed, a novel RS 3Min "all out" test appears to be a promising method for enhancing test sensitivity in cardiovascular screening after stroke, while providing a potentially valid measure of critical power.

Distinguishing Distinct Neural Systems for Proximal vs Distal Upper Extremity Motor Control After Acute Stroke

BACKGROUND AND OBJECTIVES

The classic and singular pattern of distal greater than proximal upper extremity motor deficits after acute stroke does not account for the distinct structural and functional organization of circuits for proximal and distal motor control in the healthy CNS. We hypothesized that separate proximal and distal upper extremity clinical syndromes after acute stroke could be distinguished and that patterns of neuroanatomical injury leading to these 2 syndromes would reflect their distinct organization in the intact CNS.

METHODS

Proximal and distal components of motor impairment (upper extremity Fugl-Meyer score) and strength (Shoulder Abduction Finger Extension score) were assessed in consecutively recruited patients within 7 days of acute stroke. Partial correlation analysis was used to assess the relationship between proximal and distal motor scores. Functional outcomes including the Box and Blocks Test (BBT), Barthel Index (BI), and modified Rankin scale (mRS) were examined in relation to proximal vs distal motor patterns of deficit. Voxel-based lesion-symptom mapping was used to identify regions of injury associated with proximal vs distal upper extremity motor deficits.

RESULTS

A total of 141 consecutive patients (49% female) were assessed 4.0 ± 1.6 (mean ± SD) days after stroke onset. Separate proximal and distal upper extremity motor components were distinguishable after acute stroke (p = 0.002). A pattern of proximal more than distal injury (i.e., relatively preserved distal motor control) was not rare, observed in 23% of acute stroke patients. Patients with relatively preserved distal motor control, even after controlling for total extent of deficit, had better outcomes in the first week and at 90 days poststroke (BBT, ρ = 0.51, p < 0.001; BI, ρ = 0.41, p < 0.001; mRS, ρ = 0.38, p < 0.001). Deficits in proximal motor control were associated with widespread injury to subcortical white and gray matter, while deficits in distal motor control were associated with injury restricted to the posterior aspect of the precentral gyrus, consistent with the organization of proximal vs distal neural circuits in the healthy CNS.

DISCUSSION

These results highlight that proximal and distal upper extremity motor systems can be selectively injured by acute stroke, with dissociable deficits and functional consequences. Our findings emphasize how disruption of distinct motor systems can contribute to separable components of poststroke upper extremity hemiparesis.

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.

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.

Abstract 152: Relationship Between Gait Function And Damage To Descending Motor Pathways After Stroke

Introduction: Descending motor pathways, namely the corticospinal (CST) and corticoreticular tracts (CRT), are important for normal gait function and have been implicated in gait recovery after stroke. However, the relationship of structural injury to these tracts and gait function in the acute and chronic stage post-stroke remains unclear.

Methods: Gait velocity was recorded the first week (acute) after stroke (n=127) and one year later (n= 50). CST and CRT injury were measured using weighted lesion load (wLL). The impact of CST and CRT injury on ambulation status (non-ambulatory vs. ambulatory) and gait velocity was assessed with multivariate logistic and linear regression models, respectively, acutely and chronically, controlling for wLL and lesion size.

Results: Greater CRT injury resulted in a higher odds of ambulation loss acutely post-stroke (odds ratio [95% CI, p value]: CRT wLL, 1.06 [1.02-1.12, 0.007]; CST wLL 0.97 [0.95-0.99, 0.04]; lesion volume 1.00 [0.99-1.00, 0.96]). Conversely, greater CST injury had higher odds of ambulation loss at one-year (CST wLL, 1.09 [1.01-1.21, 0.04]; CRT wLL, 0.98 [0.84-1.13, 0.75]; lesion volume, 1.00 [0.99-1.00, 0.81]). For walkers (N=51 [acute] and 46 [chronic]), gait velocity was not significantly associated with CRT nor CST wLL at either time. Multicollinearity results denoted lesion measures provided independent information (maximum variance inflation factors 3.4 (acute), 4.2 (one-year)).

Conclusion: Results suggest CRT injury is the dominant correlate of ambulation loss acutely, with CST the dominant correlate of persistent loss after one-year. Gait velocity is not well explained by damage to either tract. The results imply that the CRT may be the primary cortical projection for normal (pre-stroke) gait. Yet, the nervous system has sufficient redundancy to compensate for unilateral CRT injury, while CST injury may have a more enduring negative impact on gait function.

Walk the Talk: Current Evidence for Walking Recovery After Stroke, Future Pathways and a Mission for Research and Clinical Practice

Achieving safe, independent, and efficient walking is a top priority for stroke survivors to enable quality of life and future health. This narrative review explores the state of the science in walking recovery after stroke and potential for development. The importance of targeting walking capacity and performance is explored in relation to individual stroke survivor gait recovery, applying a common language, measurement, classification, prediction, current and future intervention development, and health care delivery. Findings are summarized in a model of current and future stroke walking recovery research and a mission statement is set for researchers and clinicians to drive the field forward to improve the lives of stroke survivors and their carers.

Serial Backward Locomotor Treadmill Training Improves Bidirectional Walking Performance in Chronic Stroke

Background and Research Question

Walking impairment remains a major limitation to functional independence after stroke. Yet, comprehensive and effective strategies to improve walking function after stroke are presently limited. Backward Locomotor Treadmill Training (BLTT) is a promising training approach for improving walking function; however, little is known about its mechanism of effect or the relationship between backward walking training and resulting overground forward walking performance. This study aims to determine the effects of serial BLTT on spatial aspects of backward and forward walking in chronic post-stroke individuals with residual walking impairment.

Methods

Thirty-nine adults (>6 months post-stroke) underwent 6 days of BLTT (3 × /week) over 2 weeks. Outcome measures included PRE-POST changes in backward and forward walking speeds, paretic and non-paretic step lengths, and single-support center of pressure distances. To determine the association between BLTT and overground walking, correlation analyses comparing training-related changes in these variables were performed.

Results

We report an overall improvement in BLTT and overground walking speeds, bilateral step lengths, and single-support center of pressure distances over six training sessions. Further, there were weak positive associations between PRE-POST changes in BLTT speed, BLTT paretic step length, and overground forward walking speed.

Conclusion and Significance

Our findings suggest that individuals with chronic post-stroke walking impairment experience improvements in spatial walking measures during BLTT and overground. Therefore, BLTT may be a potential adjunctive training approach for post-stroke walking rehabilitation.

Mapping the human corticoreticular pathway with multimodal delineation of the gigantocellular reticular nucleus and high-resolution diffusion tractography

The corticoreticular pathway (CRP) is a major motor tract that transmits cortical input to the reticular formation motor nuclei and may be an important mediator of motor recovery after central nervous system damage. However, its cortical origins, trajectory and laterality are incompletely understood in humans. This study aimed to map the human CRP and generate an average CRP template in standard MRI space. Following recently established guidelines, we manually delineated the primary reticular formation motor nucleus (gigantocellular reticular nucleus [GRN]) using several group-mean MRI contrasts from the Human Connectome Project (HCP). CRP tractography was then performed with HCP diffusion-weighted MRI data (N = 1065) by selecting diffusion streamlines that reached both the cortex and GRN. Corticospinal tract (CST) tractography was also performed for comparison. Results suggest that the human CRP has widespread origins, which overlap with the CST across most of the motor cortex and include additional exclusive inputs from the medial and anterior prefrontal cortices. The estimated CRP projected through the anterior and posterior limbs of the internal capsule before partially decussating in the midbrain tegmentum and converging bilaterally on the pontomedullary reticular formation. Thus, the CRP trajectory appears to partially overlap the CST, while being more distributed and anteromedial to the CST in the cerebrum before moving posterior to the CST in the brainstem. These findings have important implications for neurophysiologic testing, cortical stimulation and movement recovery after brain lesions. We expect that our GRN and tract maps will also facilitate future CRP research.

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.

Abstract TP10: Inflammatory And Neurodegenerative Gene Expression Changes Occur Long-term After ICH

Objective: There is a high prevalence of progressive cognitive impairment in intracerebral hemorrhage (ICH) survivors. We sought to identify gene expression changes, in association with long-term neurodegeneration, among patients 12-24 months post-ICH.

Methods: The Recovery and Outcomes from StrokE (ROSE) study prospectively recruits patients with spontaneous, supratentorial ICH, collecting baseline peripheral blood samples and MRI with diffusion tract imaging (DTI). The Recovery of StrokE-Longitudinal Assessment with Neuroimaging (ROSE-LAWN) study performs long term follow-up at 12-24 months on cases enrolled in ROSE. We report on the first five cases enrolled in the ROSE-LAWN study from December 2020 to March 2021. Controls were matched to an overall ICH population by age, sex, and race. RNA-sequencing, aligned to human genome assembly GRCh38, was tested for differential gene expression. Canonical pathway enrichment and network analyses were computed for differentially expressed genes using Ingenuity Pathway Analysis, STRING and MCODE.

Results: RNA-seq analysis of 5 ICH cases [male, 80%; median age, 61 (45 - 73); black, 40%; ICH volume, 14.88cc ± 13.07] and 13 controls [male, 54%; median age, 74 (69 - 79); black, 15%] identified 554 differentially expressed genes (genomic control adjusted p < 0.01), of which 24 met the false discovery rate correction for multiple comparisons (FDR < 0.05). The most significant difference was observed in hypoxia up-regulated 1 ( HYOU1), a heat shock protein related gene (p = 2.64E-11). Pathway analysis identified enrichment of dopamine and serotonin receptor signaling (p = 8.74E-03, 2.23E-02), cell cycle regulation (p = 1.75E-02) and agranulocyte adhesion pathways (p = 2.18E-02). Comparison of baseline and follow-up MRI DTI demonstrated extensive cortical tract degeneration, beyond the initial injury.

Conclusion: These results provide novel evidence of significant gene expression changes occurring years after the initial ICH. Despite resolution of the ICH, persistent inflammation may correlate with progressive neurodegeneration and subsequent cognitive impairment in ICH survivors. Future studies with greater sample sizes are supported by this work.

Backward Locomotor Treadmill Training Differentially Improves Walking Performance across Stroke Walking Impairment Levels

Background: Post-stroke walking impairment is a significant cause of chronic disability worldwide and often leads to loss of life roles for survivors and their caregivers. Walking impairment is traditionally classified into mild (>0.8 m/s), moderate (0.41–0.8 m/s), and severe (≤0.4 m/s), and those categorized as “severe” are more likely to be homebound and at greater risk of falls, fractures, and rehospitalization. In addition, there are minimal effective walking rehabilitation strategies currently available for this subgroup. Backward locomotor treadmill training (BLTT) is a novel and promising training approach that has been demonstrated to be safe and feasible across all levels of impairment; however, its benefits across baseline walking impairment levels (severe (≤0.4 m/s) vs. mild–moderate (>0.4 m/s)) have not been examined. Methods: Thirty-nine adults (>6 months post-stroke) underwent 6 days of BLTT (3×/week) over 2 weeks. Baseline and PRE to POST changes were measured during treadmill training and overground walking. Results: Individuals with baseline severe walking impairment were at a more significant functional disadvantage across all spatiotemporal walking measures at baseline and demonstrated fewer overall gains post-training. However, contrary to our working hypothesis, both groups experienced comparable increases in cadence, bilateral percent single support times, and step lengths. Conclusion: BLTT is well tolerated and beneficial across all walking impairment levels, and baseline walking speed (≤0.4 m/s) should serve as a covariate in the design of future walking rehabilitation trials.

Mapping the corticoreticular pathway from cortex-wide anterograde axonal tracing in the mouse

The corticoreticular pathway (CRP) has been implicated as an important mediator of motor recovery and rehabilitation after central nervous system damage. However, its origins, trajectory and laterality are not well understood. This study mapped the mouse CRP in comparison with the corticospinal tract (CST). We systematically searched the Allen Mouse Brain Connectivity Atlas (© 2011 Allen Institute for Brain Science) for experiments that used anterograde tracer injections into the right isocortex in mice. For each eligible experiment (N = 607), CRP and CST projection strength were quantified by the tracer volume reaching the reticular formation motor nuclei (RF_motor ) and pyramids, respectively. Tracer density in each brain voxel was also correlated with RF_motor versus pyramids projection strength to explore the relative trajectories of the CRP and CST. We found significant CRP projections originating from the primary and secondary motor cortices, anterior cingulate, primary somatosensory cortex, and medial prefrontal cortex. Compared with the CST, the CRP had stronger projections from each region except the primary somatosensory cortex. Ipsilateral projections were stronger than contralateral for both tracts (above the pyramidal decussation), but the CRP projected more bilaterally than the CST. The estimated CRP trajectory was anteromedial to the CST in the internal capsule and dorsal to the CST in the brainstem. Our findings reveal a widespread distribution of CRP origins and confirm strong bilateral CRP projections, theoretically increasing the potential for partial sparing after brain lesions and contralesional compensation after unilateral injury.

Moderate-intensity exercise versus high-intensity interval training to recover walking post-stroke: protocol for a randomized controlled trial

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.govNCT03760016. Registered on November 30, 2018.

Functional magnetic resonance brain imaging of imagined walking to study locomotor function after stroke

OBJECTIVE

Imagined walking has yielded insights into normal locomotor control and could improve understanding of neurologic gait dysfunction. This study evaluated brain activation during imagined walking in chronic stroke.

METHODS

Ten persons with stroke and 10 matched controls completed a walking test battery and a magnetic resonance imaging session including imagined walking and knee extension tasks. Brain activations were compared between tasks and groups. Associations between activations and composite gait score were also calculated, while controlling for lesion load.

RESULTS

Stroke and worse gait score were each associated with lesser overall brain activation during knee extension but greater overall activation during imagined walking. During imagined walking, the stroke group significantly activated the primary motor cortex lower limb region and cerebellar locomotor region. Better walking function was associated with less activation of these regions and greater activation of medial superior frontal gyrus area 9.

CONCLUSIONS

Compared with knee extension, imagined walking was less sensitive to stroke-related deficits in brain activation but better at revealing compensatory changes, some of which could be maladaptive.

SIGNIFICANCE

The identified associations for imagined walking suggest potential neural mechanisms of locomotor adaptation after stroke, which could be useful for future intervention development and prognostication.

The Impact of Sleep Disorders on Functional Recovery and Participation Following Stroke: A Systematic Review and Meta-Analysis

Background

Adequate sleep is vital for health and quality of life. People with stroke and a concomitant sleep disorder may have poorer outcomes than those without a sleep disorder.

Objective

To systematically evaluate the published literature to determine the impact of sleep disorders on physical, functional recovery at the activity and participation level after stroke.

Methods

A systematic review was conducted using PubMed, CINAHL, Scopus, and PsycINFO. Studies were selected that reported outcomes on physical, functional recovery at the activity and participation levels in participants with stroke and a diagnosed sleep disorder. A meta-analysis was performed on included studies that reported Barthel Index (BI) and modified Rankin Scale (mRS) scores. Results: A total of 33 studies were included in the systematic review with 9 of them in the meta-analysis. The mean mRS score was 0.51 points higher in participants with stroke and sleep disorders versus participants with stroke without sleep disorder [95% CI: 0.23-0.78]. The mean BI score was 10.2 points lower in participants with stroke and sleep disorders versus participants with stroke without sleep disorder [95% CI: −17.9 to −2.6].

Conclusions

People with stroke and a sleep disorder have greater functional limitations and disability than those without a sleep disorder. Rehabilitation professionals should screen their patients with stroke for potential sleep disorders and further research is needed to develop sleep and rehabilitation interventions that can be delivered in combination. PROSPERO registration number: CRD42019125562.

Backward locomotor treadmill training combined with transcutaneous spinal direct current stimulation in stroke: a randomized pilot feasibility and safety study

Walking impairment impacts nearly 66% of stroke survivors and is a rising cause of morbidity worldwide. Despite conventional post-stroke rehabilitative care, the majority of stroke survivors experience continued limitations in their walking speed, temporospatial dynamics and walking capacity. Hence, novel and comprehensive approaches are needed to improve the trajectory of walking recovery in stroke survivors. Herein, we test the safety, feasibility and preliminary efficacy of two approaches for post-stroke walking recovery: backward locomotor treadmill training and transcutaneous spinal direct current stimulation. In this double-blinded study, 30 chronic stroke survivors (>6 months post-stroke) with mild-severe residual walking impairment underwent six 30-min sessions (three sessions/week) of backward locomotor treadmill training, with concurrent anodal (N = 19) or sham transcutaneous spinal direct current stimulation (N = 11) over the thoracolumbar spine, in a 2:1 stratified randomized fashion. The primary outcomes were: per cent participant completion, safety and tolerability of these two approaches. In addition, we collected data on training-related changes in overground walking speed, cadence, stride length (baseline, daily, 24-h post-intervention, 2 weeks post-intervention) and walking capacity (baseline, 24-h post-intervention, 2 weeks post-intervention), as secondary exploratory aims testing the preliminary efficacy of these interventions. Eighty-seven per cent (N = 26) of randomized participants completed the study protocol. The majority of the study attrition involved participants with severe baseline walking impairment. There were no serious adverse events in either the backward locomotor treadmill training or transcutaneous spinal direct current stimulation approaches. Also, both groups experienced a clinically meaningful improvement in walking speed immediately post-intervention that persisted at the 2-week follow-up. However, in contrast to our working hypothesis, anodal-transcutaneous spinal direct current stimulation did not enhance the degree of improvement in walking speed and capacity, relative to backward locomotor treadmill training + sham, in our sample. Backward locomotor treadmill training and transcutaneous spinal direct current stimulation are safe and feasible approaches for walking recovery in chronic stroke survivors. Definitive efficacy studies are needed to validate our findings on backward locomotor treadmill training-related changes in walking performance. The results raise interesting questions about mechanisms of locomotor learning in stroke, and well-powered transcutaneous spinal direct current stimulation dosing studies are needed to understand better its potential role as a neuromodulatory adjunct for walking rehabilitation.

Locomotor training intensity after stroke: Effects of interval type and mode

Background and Objectives: High-intensity interval training (HIIT) is a promising strategy for improving gait and fitness after stroke, but optimal parameters remain unknown. We tested the effects of short vs long interval type and over-ground vs treadmill mode on training intensity. Methods: Using a repeated measures design, 10 participants with chronic hemiparesis performed 12 HIIT sessions over 4 weeks, alternating between short and long-interval HIIT sessions. Both protocols included 10 minutes of over-ground HIIT, 20 minutes of treadmill HIIT and another 10 minutes over-ground. Short-interval HIIT involved 30 second bursts at maximum safe speed and 30-60 second rest periods. Long-interval HIIT involved 4-minute bursts at ~90% of peak heart rate (HR_peak) and 3-minute recovery periods at ~70% HR_peak. Results: Compared with long-interval HIIT, short-interval HIIT had significantly faster mean overground speeds (0.75 vs 0.67 m/s) and treadmill speeds (0.90 vs 0.51 m/s), with similar mean treadmill HR (82.9 vs 81.8%HR_peak) and session perceived exertion (16.3 vs 16.3), but lower overground HR (78.4 vs 81.1%HR_peak) and session step counts (1481 vs 1672). For short-interval HIIT, training speeds and HR were significantly higher on the treadmill vs. overground. For long-interval HIIT, the treadmill elicited HR similar to overground training at significantly slower speeds. Conclusions: Both short and long-interval HIIT elicit high intensities but emphasize different dosing parameters. From these preliminary findings and previous studies, we hypothesize that overground and treadmill short-interval HIIT could be optimal for improving gait speed and overground long-interval HIIT could be optimal for improving gait endurance.

Effects of Exercise Intensity on Acute Circulating Molecular Responses Poststroke

Background. Exercise intensity can influence functional recovery after stroke, but the mechanisms remain poorly understood. Objective. In chronic stroke, an intensity-dependent increase in circulating brain-derived neurotrophic factor (BDNF) was previously found during vigorous exercise. Using the same serum samples, this study tested acute effects of exercise intensity on other circulating molecules related to neuroplasticity, including vascular-endothelial growth factor (VEGF), insulin-like growth factor-1 (IGF1), and cortisol, with some updated analyses involving BDNF. Methods. Using a repeated-measures design, 16 participants with chronic stroke performed 3 exercise protocols in random order: treadmill high-intensity interval training (HIT-treadmill), seated-stepper HIT (HIT-stepper), and treadmill moderate-intensity continuous exercise (MCT-treadmill). Serum molecular changes were compared between protocols. Mediation and effect modification analyses were also performed. Results. VEGF significantly increased during HIT-treadmill, IGF1 increased during both HIT protocols and cortisol nonsignificantly decreased during each protocol. VEGF response was significantly greater for HIT-treadmill versus MCT-treadmill when controlling for baseline. Blood lactate positively mediated the effect of HIT on BDNF and cortisol. Peak treadmill speed positively mediated effects on BDNF and VEGF. Participants with comfortable gait speed ≥0.4 m/s had significantly lower VEGF and higher IGF1 responses, with a lower cortisol response during MCT-treadmill. Conclusions. BDNF and VEGF are promising serum molecules to include in future studies testing intensity-dependent mechanisms of exercise on neurologic recovery. Fast training speed and anaerobic intensity appear to be critical ingredients for eliciting these molecular responses. Serum molecular response differences between gait speed subgroups provide a possible biologic basis for previously observed differences in training responsiveness.

Effect of subthalamic deep brain stimulation on posture in Parkinson's disease: A blind computerized analysis

INTRODUCTION

We sought to assess the effect of subthalamic deep brain stimulation (STN DBS) on Parkinson's disease (PD)-associated postural abnormalities.

METHODS

A computerized analysis of posture was used to quantify the thoracolumbar, thoracic, and cervical-occipital ventral angles, as well as the thoracolumbar and cervical-occipital lateral angles from the video-repository of three specialized movement disorder centers (n = 158 patients). Data was extracted from frames from video-recordings in the pre-surgical medication-ON (dopaminergic therapy) and post-surgical stimulation-ON/medication-ON states (STN DBS plus dopaminergic therapy). The sum of the five postural angles (global postural angle) was used to compare pre-vs. post-surgical trunk posture alterations. A multivariate analysis was used to examine the association between changes in the postural angles and demographic or clinical variables.

RESULTS

There was a 6.7% amelioration in the global postural angle between the pre- and post-surgical assessments (p = 0.031). Motor response to and pre-surgical dosage of levodopa, male gender, and shorter PD duration were identified as predictors for posture improvement after STN DBS. Cases meeting criteria for lower (n = 2) or upper (n = 1) camptocormia respectively improved by 48.1% in the ventral thoracolumbar angle (from 36.4 ± 0.0° to 18.9 ± 4.2°) and 13.8% in the ventral thoracic angle (from 49.1° to 42.3°). Cases meeting criteria for Pisa syndrome (n = 2) improved by 67.5% in the lateral thoracolumbar angle (from 16.9 ± 2.0° to 5.5 ± 4.7°).

CONCLUSIONS

STN DBS has a relatively small but significant effect on PD-associated postural abnormalities, potentially enhancing the effect of dopaminergic medications alone.

Exercise intensity affects acute neurotrophic and neurophysiological responses poststroke

Aerobic exercise may acutely prime the brain to be more responsive to rehabilitation, thus facilitating neurologic recovery from conditions like stroke. This aerobic priming effect could occur through multiple mechanisms, including upregulation of circulating brain-derived neurotrophic factor (BDNF), increased corticospinal excitability, and decreased intracortical inhibition. However, optimal exercise parameters for targeting these mechanisms are poorly understood. This study tested the effects of exercise intensity on acute BDNF and neurophysiological responses. Sixteen ambulatory persons >6 mo poststroke performed three different 20-min exercise protocols in random order, approximately 1 wk apart, including the following: 1) treadmill high-intensity interval training (HIT-treadmill); 2) seated-stepper HIT (HIT-stepper); and 3) treadmill moderate-intensity continuous exercise (MCT-treadmill). Serum BDNF and transcranial magnetic stimulation measures of paretic lower limb excitability and inhibition were assessed at multiple time points during each session. Compared with MCT-treadmill, HIT-treadmill elicited significantly greater acute increases in circulating BDNF and corticospinal excitability. HIT-stepper initially showed BDNF responses similar to HIT-treadmill but was no longer significantly different from MCT-treadmill after decreasing the intensity in reaction to two hypotensive events. Additional regression analyses showed that an intensity sufficient to accumulate blood lactate appeared to be important for eliciting BDNF responses, that the interval training approach may have facilitated the corticospinal excitability increases, and that the circulating BDNF response was (negatively) related to intracortical inhibition. These findings further elucidate neurologic mechanisms of aerobic exercise and inform selection of optimal exercise-dosing parameters for enhancing acute neurologic effects. NEW & NOTEWORTHY Acute exercise-related increases in circulating BDNF and corticospinal excitability are thought to prime the brain for learning. Our data suggest that these responses can be obtained among persons with stroke using short-interval treadmill high-intensity interval training, that a vigorous aerobic intensity sufficient to generate lactate accumulation is needed to increase BDNF, that interval training facilitates increases in paretic quadriceps corticospinal excitability, and that greater BDNF response is associated with lesser intracortical inhibition response.

Resting-state functional connectivity of subcortical locomotor centers explains variance in walking capacity

Walking capacity influences the quality of life and disability in normal aging and neurological disease, but the neural correlates remain unclear and subcortical locomotor regions identified in animals have been more challenging to assess in humans. Here we test whether resting-state functional MRI connectivity (rsFC) of midbrain and cerebellar locomotor regions (MLR and CLR) is associated with walking capacity among healthy adults. Using phenotypic and MRI data from the Nathan Kline Institute Rockland Sample (n =119, age 18-85), the association between walking capacity (6-min walk test distance) and rsFC was calculated from subcortical locomotor regions to 81 other gait-related regions of interest across the brain. Additional analyses assessed the independence and specificity of the results. Walking capacity was associated with higher rsFC between the MLR and superior frontal gyrus adjacent to the anterior cingulate cortex, higher rsFC between the MLR and paravermal cerebellum, and lower rsFC between the CLR and primary motor cortex foot area. These rsFC correlates were more strongly associated with walking capacity than phenotypic variables such as age, and together explained 25% of the variance in walking capacity. Results were specific to locomotor regions compared with the other brain regions. The rsFC of locomotor centers correlates with walking capacity among healthy adults. These locomotion-related biomarkers may prove useful in future work aimed at helping patients with reduced walking capacity.

Preliminary safety analysis of high-intensity interval training (HIIT) in persons with chronic stroke

The purpose of this study was to assess safety via electrocardiographic (ECG), blood pressure (BP), heart rate (HR), and orthopedic responses to 3 different high-intensity interval training (HIIT) protocols in persons with stroke. Eighteen participants (10 male; 61.9 + 8.3 years of age; 5.8 + 4.2 years poststroke) completed a symptom-limited graded exercise test (GXT) with ECG monitoring to screen for eligibility and determine HR peak. The 3 HIIT protocols involved repeated 30 s bursts of treadmill walking at maximum speed alternated with rest periods of 30 s (P30), 1 min (P60), or 2 min (P120). Sessions were performed in random order and included 5 min warm up, 20 min HIIT, and 5 min cool down. Variables measured included ECG activity, BP, HR, signs and symptoms of cardiovascular intolerance, and orthopedic concerns. Generalized linear mixed models and Tukey–Kramer adjustment were used to compare protocols using p < 0.05. No signs or symptoms of cardiovascular intolerance, significant arrhythmias, ST segment changes, or orthopedic responses resulted in early termination of any HIIT session. HIIT elicited HRs in excess of 88% of measured HRpeak including 6 (P30), 8 (P60), and 2 (P120) participants eliciting a HR response above their GXT HRpeak. Both maximum BP and HR were significantly higher in P30 and P60 relative to P120. Preliminary data indicate that persons with chronic stroke who have been prescreened with an ECG stress test, a symptom-limited GXT, and a harness for fall protection may safely participate in HIIT, generating substantially higher HRs than what is seen in traditional moderate intensity training.

Abstract WP170: Identifying the "New Norm" of Cardiac Rehabilitation after Stroke

Background and Purpose: Physical inactivity after stroke stymies motor recovery, perpetuates further deconditioning, and contributes to a high long-term risk of cardiac events and recurrent stroke. This study used stakeholder input to develop a cardiac rehabilitation program specific to stroke.

Methods: An exploratory qualitative study was performed consisting of separate focus groups of stroke survivors, caregivers, rehabilitation clinicians, nurse practitioners along with individual physician interviews. Two experienced researchers in qualitative research methodology independently identified themes, patterns, and issues prioritized by participants.

Results: Four major themes emerged: safety, individualization of the cardiac rehabilitation program, return to function and living at highest potential, and need to maintain prolonged activity. Major components identified in developing the cardiac rehabilitation program included: Individualized stroke survivor education pertaining to fall prevention, safe aerobic exercise and learning how to live well after stroke (e.g., fitness, nutrition, chronic disease management, etc.); Exercise/stress testing prior to aerobic exercise; Determine when to begin cardiac rehabilitation post stroke (e.g., readiness, needs, resources, benefit, etc.), individualize approach and timing after holistic assessment; Education/training of cardiac rehabilitation professionals regarding best care practices for stroke survivors; Interdisciplinary approach to assure safety and continuum of care; Referral programs for IADLs, driving, sexual function, etc.; Motivational interviewing to overcome barriers with inclusion of peer mentoring/coaching; Discharge to cost effective community programs or a sustainable home program.

Conclusions: Addressing safety concerns along with the creation of an individualized cardiac rehabilitation program that enables stroke survivors to achieve and maintain their highest level of function long-term are fundamental components. Partnering with the major stakeholders and incorporating a coordinated interdisciplinary approach are crucial to the creation of a feasible and cost effective cardiac rehabilitation program for stroke survivors.

Predicting Home and Community Walking Activity Poststroke

BACKGROUND AND PURPOSE

Walking ability poststroke is commonly assessed using gait speed categories developed by Perry et al. The purpose of this study was to reexamine factors that predict home and community ambulators determined from real-world walking activity data using activity monitors.

METHODS

Secondary analyses of real-world walking activity from 2 stroke trials. Home (100-2499 steps/d), most limited community (2500-4499 steps/d), least limited community (5000-74 999), and full community (≥7500 steps/d) walking categories were developed based on normative data. Independent variables to predict walking categories were comfortable and fast gait speed, 6-minute walk test, Berg Balance Scale, Fugl Meyer, and Stroke Impact Scale. Data were analyzed using multivariate analyses to identify significant variables associated with walking categories, bootstrap method to select the most stable model and receiver-operating characteristic to identify cutoff values.

RESULTS

Data from 441 individuals poststroke were analyzed. The 6-minute walk test, Fugl Meyer, and Berg Balance Scale combined were the strongest predictors of home versus community and limited versus unlimited community ambulators. The 6-minute walk test was the strongest individual variable in predicting home versus community (receiver-operating characteristic area under curve=0.82) and limited versus full community ambulators (receiver-operating characteristic area under curve=0.76). A comfortable gait speed of 0.49 m/s discriminated between home and community and a comfortable gait speed of 0.93 m/s discriminated between limited community and full community ambulators.

CONCLUSIONS

The 6-minute walk test was better able to discriminate among home, limited community, and full community ambulators than comfortable gait speed. Gait speed values commonly used to distinguish between home and community walkers may overestimate walking activity.

Factors Influencing the Efficacy of Aerobic Exercise for Improving Fitness and Walking Capacity After Stroke: A Meta-Analysis With Meta-Regression

OBJECTIVE

To assess the influence of dosing parameters and patient characteristics on the efficacy of aerobic exercise (AEX) poststroke.

DATA SOURCES

A systematic review was conducted using PubMed, MEDLINE, Cumulative Index of Nursing and Allied Health Literature, Physiotherapy Evidence Database, and Academic Search Complete.

STUDY SELECTION

Studies were selected that compared an AEX group with a nonaerobic control group among ambulatory persons with stroke.

DATA EXTRACTION

Extracted outcome data included peak oxygen consumption (V˙o₂peak) during exercise testing, walking speed, and walking endurance (6-min walk test). Independent variables of interest were AEX mode (seated or walking), AEX intensity (moderate or vigorous), AEX volume (total hours), stroke chronicity, and baseline outcome scores.

DATA SYNTHESIS

Significant between-study heterogeneity was confirmed for all outcomes. Pooled AEX effect size estimates (AEX group change minus control group change) from random effects models were V˙o₂peak, 2.2mL⋅kg^-1⋅min^-1 (95% confidence interval [CI], 1.3-3.1mL⋅kg^-1⋅min^-1); walking speed, .06m/s (95% CI, .01-.11m/s); and 6-minute walk test distance, 29m (95% CI, 15-42m). In meta-regression, larger V˙o₂peak effect sizes were significantly associated with higher AEX intensity and higher baseline V˙o₂peak. Larger effect sizes for walking speed and the 6-minute walk test were significantly associated with a walking AEX mode. In contrast, seated AEX did not have a significant effect on walking outcomes.

CONCLUSIONS

AEX significantly improves aerobic capacity poststroke, but may need to be task specific to affect walking speed and endurance. Higher AEX intensity is associated with better outcomes. Future randomized studies are needed to confirm these results.

Ventilatory threshold may be a more specific measure of aerobic capacity than peak oxygen consumption rate in persons with stroke

BACKGROUND

After stroke, aerobic deconditioning can have a profound impact on daily activities. This is usually measured by the peak oxygen consumption rate achieved during exercise testing (VO2-peak). However, VO2-peak may be distorted by motor function. The oxygen uptake efficiency slope (OUES) and VO2 at the ventilatory threshold (VO2-VT) could more specifically assess aerobic capacity after stroke, but this has not been tested.

OBJECTIVES

To assess the differential influence of motor function on three measures of aerobic capacity (VO2-peak, OUES, and VO2-VT) and to evaluate the inter-rater reliability of VO2-VT determination post-stroke.

METHODS

Among 59 persons with chronic stroke, cross-sectional correlations with motor function (comfortable gait speed [CGS] and lower extremity Fugl-Meyer [LEFM]) were compared between the different aerobic capacity measures, after adjustment for covariates, in order to isolate any distorting effect of motor function. Reliability of VO2-VT determination between three raters was assessed with intra-class correlation (ICC).

RESULTS

CGS was moderately correlated with VO2-peak (r = 0.52, p < 0.0001) and weakly correlated with OUES (r = 0.41, p = 0.002) and VO2-VT (r = 0.37, p = 0.01). LEFM was weakly correlated with VO2-peak (r = 0.26, p = 0.055) and very weakly correlated with OUES (r = 0.19, p = 0.17) and VO2-VT (r = 0.14, p = 0.31). Compared to VO2-peak, VO2-VT was significantly less correlated with CGS (r difference = -0.16, p = 0.02). Inter-rater reliability of VO2-VT determination was high (ICC: 0.93, 95% CI: 0.89-0.96).

CONCLUSIONS

Motor dysfunction appears to artificially lower measured aerobic capacity. VO2-VT seemed to be less distorted than VO2-peak and had good inter-rater reliability, so it may provide more specific assessment of aerobic capacity post-stroke.

Abstract TP143: Effects of Aerobic Exercise Intensity on Novel Blood Biomarkers of Neuroplasticity After Stroke

Introduction: Aerobic exercise (AEX) may facilitate neurologic stroke recovery. Among healthy adults, intense AEX is known to upregulate brain-derived neurotrophic factor (BDNF), a critical facilitator of neuroplasticity, motor learning and cognition. Increased blood lactate during AEX appears to be a key mechanism underlying this effect. Intense AEX also increases blood ionized calcium (Ca++). In animal studies, some of this increased Ca++ has been shown to be transported to the brain and enhance synthesis of monoamine neurotransmitters (e.g. dopamine) that are associated with neuroplasticity and motor learning. Thus, increased blood lactate and Ca++ during AEX represent potentially important biomarkers of central neurologic benefits, but neither has been previously studied in persons with stroke.

Hypothesis: High intensity AEX will elicit significantly larger lactate and Ca++ responses than moderate intensity in chronic stroke.

Methods: Using a crossover design, eight subjects (mean ± SD age, 57 ± 8 years; years post stroke, 8.7 ± 2.7) performed one 20 minute session each of moderate and high intensity treadmill AEX in random order. Blood lactate and Ca++ were measured at baseline and multiple time points during and after AEX. Mixed effects models were used to examine changes within and between protocols using an alpha of 0.05.

Results: Blood lactate response was significantly greater for high vs moderate intensity AEX (p<0.0001). While moderate intensity showed no significant changes with time (p=0.60), high intensity showed significant increases during and immediately after AEX (all p<0.0001). Blood Ca++ showed no significant protocol by time interaction (p=0.08) but did show a significant time effect (p<0.0001) with increases during (p<0.0001) and immediately after (p=0.01) AEX.

Conclusions: Unlike moderate intensity AEX, high intensity elicited a robust lactate response. This has promising implications for the effects of high-intensity AEX on BDNF post-stroke. Both protocols combined showed an increase in Ca++, which has promising implications for the effects of AEX on monoamine neurotransmitter synthesis after stroke.

Predicting Heart Rate at the Ventilatory Threshold for Aerobic Exercise Prescription in Persons With Chronic Stroke

BACKGROUND AND PURPOSE

Treadmill aerobic exercise improves gait, aerobic capacity, and cardiovascular health after stroke, but a lack of specificity in current guidelines could lead to underdosing or overdosing of aerobic intensity. The ventilatory threshold (VT) has been recommended as an optimal, specific starting point for continuous aerobic exercise. However, VT measurement is not available in clinical stroke settings. Therefore, the purpose of this study was to identify an accurate method to predict heart rate at the VT (HRVT) for use as a surrogate for VT.

METHODS

A cross-sectional design was employed. Using symptom-limited graded exercise test (GXT) data from 17 subjects more than 6 months poststroke, prediction methods for HRVT were derived by traditional target HR calculations (percentage of HRpeak achieved during GXT, percentage of peak HR reserve [HRRpeak], percentage of age-predicted maximal HR, and percentage of age-predicted maximal HR reserve) and by regression analysis. The validity of the prediction methods was then tested among 8 additional subjects.

RESULTS

All prediction methods were validated by the second sample, so data were pooled to calculate refined prediction equations. HRVT was accurately predicted by 80% HRpeak (R, 0.62; standard deviation of error [SDerror], 7 bpm), 62% HRRpeak (R, 0.66; SDerror, 7 bpm), and regression models that included HRpeak (R, 0.62-0.75; SDerror, 5-6 bpm).

DISCUSSION AND CONCLUSIONS

Derived regression equations, 80% HRpeak and 62% HRRpeak, provide a specific target intensity for initial aerobic exercise prescription that should minimize underdosing and overdosing for persons with chronic stroke. The specificity of these methods may lead to more efficient and effective treatment for poststroke deconditioning.Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A114).

Within-session responses to high-intensity interval training in chronic stroke

Poststroke hemiparesis often leads to a vicious cycle of limited activity, deconditioning, and poor cardiovascular health. Accumulating evidence suggests that exercise intensity is a critical factor determining gains in aerobic capacity, cardiovascular protection, and functional recovery after stroke. High-intensity interval training (HIT) is a strategy that augments exercise intensity using bursts of concentrated effort alternated with recovery periods. However, there was previously no stroke-specific evidence to guide HIT protocol selection.

PURPOSE

This study aimed to compare within-session exercise responses among three different HIT protocols for persons with chronic (>6 months after) stroke.

METHODS

Nineteen ambulatory persons with chronic stroke performed three different 1-d HIT sessions in a randomized order, approximately 1 wk apart. HIT involved repeated 30-s bursts of treadmill walking at maximum tolerated speed, alternated with rest periods. The three HIT protocols were different on the basis of the length of the rest periods, as follows: 30 s (P30), 60 s (P60), or 120 s (P120). Exercise tolerance, oxygen uptake (V˙O2), HR, peak treadmill speed, and step count were measured.

RESULTS

P30 achieved the highest mean V˙O2, HR, and step count but with reduced exercise tolerance and lower treadmill speed than P60 or P120 (P30: 70.9% V˙O2peak, 76.1% HR reserve (HRR), 1619 steps, 1.03 m·s(-1); P60: 63.3% V˙O2peak, 63.1% HRR, 1370 steps, 1.13 m·s(-1); P120: 47.5% V˙O2peak, 46.3% HRR, 1091 steps, 1.10 m·s(-1)). P60 achieved treadmill speed and exercise tolerance similar to those in P120, with higher mean V˙O2, HR, and step count.

CONCLUSIONS

For treadmill HIT in chronic stroke, a combination of P30 and P60 may optimize aerobic intensity, treadmill speed, and stepping repetition, potentially leading to greater improvements in aerobic capacity and gait outcomes in future studies.

Does aerobic exercise and the FITT principle fit into stroke recovery?

Sedentary lifestyle after stroke is common which results in poor cardiovascular health. Aerobic exercise has the potential to reduce cardiovascular risk factors and improve functional capacity and quality of life in people after stroke. However, aerobic exercise is a therapeutic intervention that is underutilized by healthcare professionals after stroke. The purpose of this review paper is to provide information on exercise prescription using the FITT principle (frequency, intensity, time, type) for people after stroke and to guide healthcare professionals to incorporate aerobic exercise into the plan of care. This article discusses the current literature outlining the evidence base for incorporating aerobic exercise into stroke rehabilitation. Recently, high-intensity interval training has been used with people following stroke. Information is provided regarding the early but promising results for reaching higher target heart rates.

Abstract W MP58: High Intensity Interval Training May Be Superior to Moderate Intensity Continuous Exercise in Chronic Stroke

Introduction: Aerobic deconditioning is a major barrier to stroke recovery. Post stroke guidelines recommend moderate intensity continuous exercise (MICE) to improve aerobic fitness and mobility. High-intensity interval training (HIT) has been shown to be more effective than MICE for improving aerobic fitness among healthy adults and persons with heart disease. However, no previous study has compared HIT and MICE among persons with stroke. We hypothesized that HIT would elicit significantly greater improvement in both aerobic fitness and gait function relative to MICE in this population.

Methods: Fourteen subjects (mean ± SD age, 58 ± 10 years; years post stroke, 4.3 ± 2.9) were randomized to HIT (n=11) or MICE (n=5); each 25 min, 3x/week for 4 weeks. HIT involved repeated 30 sec bursts of treadmill (TM) gait at maximum tolerated speed (based on gait stability), alternated with 30-60 sec rest periods. MICE involved continuous TM gait at 45-50% heart rate reserve. Outcomes were measured by a blinded rater before and after intervention, including peak oxygen uptake and ventilatory threshold during graded exercise testing, energy cost of gait, 10m walk test (comfortable and fastest speeds) and TM speed (comfortable and fastest). Mixed effects models tested for significant (p<0.05) differences over time within groups and between the groups. Standardized effect sizes were also calculated.

Results: In the HIT group, significant improvement was found for all outcomes save peak oxygen uptake. No significant differences were found in the MICE group. Ventilatory threshold and fastest TM speed improved significantly more in HIT compared to MICE and moderate to large effect sizes were found for all outcomes.

Conclusion: HIT is a potent intervention for improving aerobic fitness and gait function in chronic stroke that appears to be more effective than MICE. Further study with a larger sample is warranted.

High-intensity interval training in stroke rehabilitation

After stroke, people with weakness enter a vicious cycle of limited activity and deconditioning that limits functional recovery and exacerbates cardiovascular risk factors. Conventional aerobic exercise improves aerobic capacity, function, and overall cardiometabolic health after stroke. Recently, a new exercise strategy has shown greater effectiveness than conventional aerobic exercise for improving aerobic capacity and other outcomes among healthy adults and people with heart disease. This strategy, called high-intensity interval training (HIT), uses bursts of concentrated effort alternated with recovery periods to maximize exercise intensity. Three poststroke HIT studies have shown preliminary effectiveness for improving functional recovery. However, these studies were varied in approach and the safety of poststroke HIT has received little attention. The objectives of this narrative review are to (1) propose a framework for categorizing HIT protocols; (2) summarize the safety and effectiveness evidence of HIT among healthy adults and people with heart disease and stroke; (3) discuss theoretical mechanisms, protocol selection, and safety considerations for poststroke HIT; and (4) provide directions for future research.

Tongue-based biofeedback for balance in stroke: results of an 8-week pilot study

OBJECTIVE

To assess balance recovery and quality of life after tongue-placed electrotactile biofeedback training in patients with stroke.

DESIGN

Prospective multicenter research design.

SETTING

Outpatient rehabilitation clinics.

PARTICIPANTS

Patients (N=29) with chronic stroke.

INTERVENTIONS

Patients were administered 1 week of therapy plus 7 weeks of home exercise using a novel tongue based biofeedback balance device.

MAIN OUTCOME MEASURES

The Berg Balance Scale (BBS), Timed Up and Go (TUG), Activities-Specific Balance Confidence (ABC) Scale, Dynamic Gait Index (DGI), and Stroke Impact Scale (SIS) were performed before and after the intervention on all subjects.

RESULTS

There were statistically and clinically significant improvements from baseline to posttest in results for the BBS, DGI, TUG, ABC Scale, and some SIS domains (Mobility, Activities of Daily Living/Instrumental Activities of Daily Living, Social, Physical, Recovery domains). Average BBS score increased from 35.9 to 41.6 (P<.001), and DGI score, from 11.1 to 13.7 (P<.001). Time to complete the TUG decreased from 24.7 to 20.7 seconds (P=.002). Including the BBS, DGI, TUG, and ABC Scale, 27 subjects improved beyond the minimal detectable change with 95% certainty (MDC-95) or minimal clinically important difference (MCID) in at least 1 outcome and 3 subjects improved beyond the MDC-95 or MCID in all outcomes.

CONCLUSIONS

Electrotactile biofeedback seems to be a promising integrative method to balance training. A future randomized controlled study is needed.

Longitudinal study of serum thyroid hormone levels during normal pregnancy

We undertook a prospective longitudinal study of thyroid function in 60 normal pregnant women and measured serum concentrations of T4, triiodothyronine (T3), T-uptake, thyroxine binding globulin (TBG), free thyroxine index (FTI), free T4, albumin and thyrotropin (TSH). From these data we established reference ranges for each of these analytes for each trimester and examined the inter-relationships between laboratory measurements of thyroid function tests. We observed significant increases in serum concentrations of thyrotropin and decreases in free T4, assays commonly used as first line investigations of thyroid activity during pregnancy. However, the 95th centile intervals for both analytes remained within the reference range for nonpregnant women.

State of the art in oral and maxillofacial surgery: treatment of maxillary hypoplasia and anterior palatal and alveolar clefts

As the new millennium approaches, it seems appropriate to look back at where we have been and where we are going with the care of patients with facial deformities. None of us can deny that although changes have been made, many current treatment modalities are no more than modifications of old techniques. We are, however, poised to make dramatic improvements in the management of facial abnormalities as we enter the new century and millennium. Biotechnology, genetic manipulation, and new surgical technology will become pervasive, and perhaps we will move from "modification" of the old into a completely new era of therapeutic approaches to the care of dentofacial deformities. "Opportunities multiply as they are seized" (from Sun Tzu), and the time of opportunity is approaching. This review will attempt to look at the state of the art in cleft care and in oral and maxillofacial surgery: where we have been and where we are going. It will be clear that there is overlap between specialties and that these overlaps will become greater as new regimens in the care of facial deformities come to the forefront.