medRxiv · Mar 19, 2026

Submaximal Exercise Testing to Dose High-Intensity Interval Training After Stroke: The FAST Randomized Clinical Trial

By Bartsch BL, Engler A, Schneider N et al.

IMPORTANCE: High-intensity interval training (HIIT) improves peak oxygen uptake (VO 2 peak) and walking post-stroke. However, previous HIIT trials have primarily implemented maximal exercise testing, limiting clinical implementation. OBJECTIVE: Evaluate the preliminary efficacy of HIIT, compared to moderate-intensity continuous training (MICT) using a submaximal exercise test. Hypothesis: HIIT will produce greater improvements than MICT in VO 2 peak, vascular measures, and walking outcomes. DESIGN: This was a randomized preliminary efficacy trial conducted between July 2023 and December 2025. SETTING: University of Kansas Medical Center. PARTICIPANTS: Participants with chronic stroke, 20-85 years of age, were randomized to HIIT or MICT. INTERVENTION: HIIT and MICT were performed on a total-body recumbent stepper 3 times per week for 4 weeks, with intensity prescribed using peak power output (PPO) to achieve target heart rate zones derived from a submaximal exercise test. HIIT was performed for 25 minutes with 1-minute vigorous-intensity intervals (65-95% PPO) interspersed with 1-minute active recovery intervals. MICT was performed continuously at 45-65% PPO for 25 minutes. MAIN OUTCOMES: The primary outcome was change in predicted VO 2 peak. Secondary outcomes included middle cerebral artery velocity, peripheral vascular function, and arterial stiffness with gait speed and walking endurance as tertiary outcomes. RESULTS: Forty-nine participants (HIIT: n=25, MICT: n=24) were randomized (62.4(12.5) years, 42.9% female), attended 99.5(2.0)% of sessions, and achieved target intensity zones. No study-related serious adverse events occurred. Our results showed no significant between-group differences (p=0.54) for study outcomes. Both groups significantly improved VO 2 peak (HIIT: +1.13 mL•kg⁻¹•min⁻¹ (95% CI: 0.05-2.21), p=0.04; MICT: +1.58 mL•kg⁻¹•min⁻¹ (95% CI: 0.18-2.97), p=0.03) and with fast gait speed and walking endurance. Peripheral vascular function significantly improved following HIIT. CONCLUSIONS AND RELEVANCE: HIIT can be safely implemented in individuals with chronic stroke using a submaximal exercise test. Both HIIT and MICT elicited clinically meaningful gains in VO₂peak and walking. However, only HIIT led to a significant improvement in peripheral vascular function, suggesting a biologic signal for intensity-dependent vascular adaptation. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT05936008.

doi.org/10.64898/2026.03.17.26348646Open accessPubMed 41891032Interventions