ImportanceFor walking rehabilitation after stroke, training intensity and duration are critical dosing parameters that lack optimization.ObjectiveTo 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 ParticipantsThis 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.InterventionsParticipants 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 MeasuresThe main outcome was 6-minute walk test distance. Outcomes were assessed by blinded raters after 4, 8, and 12 weeks of training.ResultsOf 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 RelevanceThese 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 RegistrationClinicalTrials.gov Identifier: NCT03760016

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.

Purpose:Physical activity within the hospital poststroke is recommended for cardiovascular and musculoskeletal health, but no studies have examined cerebrovascular health. We hypothesized that individuals who walked farther distances (FARhigh) during the acute phase of stroke recovery in a hospital setting would have a higher resting middle cerebral artery blood velocity (MCAv) and a greater cerebrovascular response (CVR) to moderate-intensity exercise at 3 months poststroke, compared with individuals who walked shorter distances (FARlow).Methods:At 3 months poststroke, we recorded 90 seconds of resting baseline (BL) MCAv, followed by 6 minutes of moderate-intensity exercise. We calculated CVR as the change in MCAv from BL to steady-state exercise. We retrospectively collected the farthest distance walked within the hospital poststroke from the electronic medical record. Participants were classified as FARhigh or FARlow based on the average farthest walking distance.Results:Twenty participants completed the study, aged 63 (15) years. Baseline MCAv was not different between groups (P = .07). In comparison with FARlow, we report a higher CVR in FARhigh's ipsilesional ( truex¯ = 7.38 [5.42] vs  truex¯ = 2.19 [3.53], P = .02)and contralesional hemispheres ( truex¯ = 8.15 [6.37] vs  truex¯ = 2.06 [4.76], P = .04).Conclusions:Physical activity during the hospital stay poststroke may support cerebrovascular health after discharge. Prospective studies are needed to support this finding.