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

Abstract

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.

Figure 1.. CONSORT Flow Diagram

AE indicates adverse event; HIIT, high-intensity interval training; and MAT, moderate-intensity aerobic training. ^aPrior myocardial infarction with peri-infarct ischemia on most recent perfusion scan. ^bFlare-ups of preexisting back pain. ^cRecurring hamstring strain or soreness.

Figure 2.. Treatment Intensity

Values are model estimates for each bout of each session, averaging data across participants. Filled circles indicate overground 1; open circles, overground 2; and crosses, treadmill. A, Speed data are peak values within a bout. B, Steady state mean heart rate (HR) excludes the first 3 minutes of the bout. For treatment monitoring, the percentage of HR reserve (HRR) was relative to the standing resting HR and the most current peak HR, which could increase after sessions 12 and 24. Shading indicates aerobic intensity zones: orange, moderate; gray, vigorous. HIIT indicates high-intensity interval training; MAT, moderate-intensity interval training.

Figure 3.. Primary Outcome of 6-Minute Walk Test Changes During 12 Weeks of High-intensity Interval Training (HIIT) or Moderate-intensity Aerobic Training (MAT) in Patients With Chronic Stroke

Values are model estimates; error bars, 95% CIs; and shading, clinically important difference in distance (20-50 m). ^aP < .05 for the false discovery rate in between-group differences in change from baseline. ^bP < .05 for within-group change from baseline. ^cP < .05 for within-group change between consecutive time points.