A Multicenter Randomized Comparison of High-Intensity Interval Training and Moderate-Intensity Exercise to Recover Walking Post-Stroke: Results of the HIT-Stroke Trial

Abstract

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

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

“…Like previous research, 58 this suggests that optimal LT mv delivery may include both treadmill and overground training. Our results also hinted that vigorous LT mv intensity may be superior to moderate intensity (like other research 59 ), but training intensity was difficult to determine from many of the reports, could only be tested for its association with 6MWT effect sizes and was not a significant factor (p=0.08).…”

Aerobic exercise training selectively improves cortical inhibitory function after stroke

“…Reporting of primary and secondary clinical outcomes for the full participant cohort are detailed in Boyne et al (2022). 31 The subset of participants in the present ancillary study produced a mean blood lactate level of 2.42±1. 35…”

“…31 A detailed trial protocol has been described in Miller et al (2021) 35 and primary endpoint analyses for the full participant cohort are described in Boyne et al, 2022. 31 Briefly, participants (40-80 years old) sustained a single stroke 6mo-5yrs prior to consent, could walk at least 10 meters with no physical assistance, were of stable cardiovascular condition, and possessed no other neurologic diagnoses or significant musculoskeletal pain with exercise. 31 The experimental protocols for the primary and ancillary study protocols were approved by the University of Kansas Medical Center Institutional Review Board and all participants provided written, informed consent (UC IRB 2017-5325; KUMC IRB MOD00023271; STUDY00143669).…”

“…The exercise intervention methods are thoroughly detailed in the protocol and primary outcomes papers for the present study. 31,35 Briefly, following baseline assessments participants were randomized to exercise training consisting of either high-intensity interval or moderate-intensity continuous walking exercise intervention arms. The aim of this ancillary study was to investigate behavioral and neurophysiologic metrics of cortical function with exercise training, thus participants from both intensity groups were pooled together.…”

“…No long-term follow-up testing occurred to determine whether improved inhibitory response time cost was further enhanced with additional training as part of the primary study RCT (e.g. 8-weeks, 12-weeks of training) 31 or whether there were sustained effects after completing the intervention. Thus, results should be interpreted cautiously and a larger RCT with controls, additional assessments, and follow-up retention testing would be needed to confirm and expand these findings.…”