Effects of High-Intensity Interval Training After Stroke (The HIIT Stroke Study) on Physical and Cognitive Function: A Multicenter Randomized Controlled Trial

To assess the effects of high-intensity interval training (HIIT) on physical, mental, and cognitive functioning after stroke. The HIIT Stroke Study was a single-blind, multicenter, parallel-group randomized controlled trial. Specialized rehabilitation units at 3 Norwegian hospitals. Adult stroke survivors (N=70) 3 months to 5 years after a first-ever stroke. Mean age was 57.6±9.2 years and 58.7±9.2 years in the intervention and control groups, respectively. Participants were randomized to standard care in combination with 4×4 minutes of treadmill HIIT at 85%-95% of peak heart rate or standard care only. Outcomes were measured using physical, mental, and cognitive tests and the FIM and Stroke Impact Scale. Linear mixed models were used to analyze differences between groups at posttest and 12-month follow-up. The intervention group showed a significant treatment effect (95% confidence interval [CI]) from baseline to posttest on a 6-minute walk test of 28.3 (CI, 2.80-53.77) meters (P=.030); Berg Balance Scale 1.27 (CI, 0.17-2.28) points (P=.025); and Trail Making Test Part B (TMT-B; −24.16 [CI, −46.35 to −1.98] s, P=.033). The intervention group showed significantly greater improvement on TMT-B at the 12-month follow-up (25.44 [CI, −49.01 to −1.87] s, P=.035). The control group showed significantly greater improvement in total Functional Independence Measure score with a treatment effect of −2.37 (CI, −4.30 to −0.44) points (P=.016) at 12-month follow-up. No significant differences were identified between groups on other outcomes at any time point. HIIT combined with standard care improved walking distance, balance, and executive function immediately after the intervention compared with standard care only. However, only TMT-B remained significant at the 12-month follow-up.