Cardiorespiratory Fitness Benefits of High-Intensity Interval Training After Stroke: A Randomized Controlled Trial

BACKGROUND: Limited evidence supports the effects of short-interval high-intensity interval training (HIIT) for improving cardiorespiratory fitness (V̇O 2 peak) after stroke. We aimed to compare the effects of 12 weeks of short-interval HIIT versus moderate-intensity continuous training (MICT) on V̇O 2 peak, cardiovascular risk factors, and mobility outcomes among individuals ≥6 months poststroke. METHODS: This study was a multi-site, 12-week randomized controlled trial (NCT03614585) with an 8-week follow-up. Participants were randomized into 3 d/wk of HIIT (10×1 minute 80%–100% heart rate reserve interspersed with 1 minute 30% heart rate reserve [19 minutes]) or MICT (20–30 minutes 40%–60% heart rate reserve). Secondary outcomes of the trial, including V̇O 2 peak, cardiovascular risk factors (carotid-femoral pulse wave velocity, blood pressure, and waist-hip ratio), and mobility (6-minute walk test, 10 m gait speed), were reported. Linear mixed model analyses with a group×study time point interaction evaluated between-group differences. RESULTS: Of the 305 potential participants, 82 consented (mean [SD] age 64.9 [9.3] years, 32 females [39%], 1.8 [1.2] years poststroke) and were randomized to HIIT (n=42, mean [SD] baseline V̇O 2 peak 17.3 [5.9] mL/kg·min) or MICT (n=40, mean [SD] baseline V̇O 2 peak 17.2 [6.0] mL/kg·min). Participants attended 82% of visits (n=2417/2952). No adverse events occurred during the study period. A significant group×study time point interaction was found (χ 2 =8.46; P =0.015) for V̇O 2 peak at 12 weeks (mean difference, 1.81 [95% CI, 0.58–3.04]; P =0.004) whereby the HIIT group had greater gains in V̇O 2 peak (∆3.52 mL/kg·min [95% CI, 2.47–4.57]; P <0.001) compared with the MICT group (∆1.71 mL/kg·min [95% CI, 0.55–2.86]; P =0.001). There was no between-group difference in V̇O 2 peak (mean difference, 1.08 [95% CI, −0.26 to 2.42]; P =0.11) at 8-week follow-up. No group×study time point interactions were found for cardiovascular risk factors or mobility outcomes. CONCLUSIONS: Short-interval HIIT may be an effective alternative to MICT for improving V̇O 2 peak at 12 weeks postintervention. REGISTRATION: URL: https://clinicaltrials.gov ; Unique identifier: NCT03614585.