# Submaximal Exercise Testing to Dose High-Intensity Interval Training After Stroke: The FAST Randomized Clinical Trial PMID: 41891032 Journal: medRxiv : the preprint server for health sciences Published: 2026-03-19 Authors: Bartsch BL, Engler A, Schneider N, Britton-Carpenter AJ, Baldridge T, Montgomery RN, Vidoni ED, Moores A, Vetter ES, Hazen EM, Abraham M, Billinger SA ## Question In adults with chronic stroke, does HIIT dosed from a total-body recumbent-stepper submaximal exercise test improve predicted VO2peak, vascular measures, and walking outcomes more than moderate-intensity continuous training? ## Summary In 49 adults with chronic stroke, 4 weeks of supervised recumbent-stepper HIIT prescribed from a submaximal exercise test was compared with moderate continuous training. Both groups trained 3 times weekly, attended nearly all sessions, achieved target intensity, improved predicted VO2peak and walking outcomes, and had no study-related serious adverse events. HIIT did not outperform MICT for the primary fitness outcome over 4 weeks, but HIIT showed within-group improvement in peripheral flow-mediated dilation. ## Population - Community-dwelling adults with chronic ischemic or hemorrhagic stroke at least 6 months prior to enrollment. - Sample size: 49 - Age: Mean 62.4 years (SD 12.5), range 35-82. - Sex: 42.9% female overall. - Fitness level: Post-stroke clinical cohort with baseline predicted VO2peak about 22-25 mL/kg/min by group. - Health status: Chronic stroke with frequent cardiovascular risk factors. ## Methodology - Single-site randomized parallel-group preliminary efficacy trial comparing HIIT with MICT. - 4 weeks of training, with post-intervention assessment within 1 week. - University of Kansas Medical Center. - Randomized and controlled study design. ## Protocol - HIIT. - Modality: Total-body recumbent stepper. - Work intervals: 1 minute at 65%-95% PPO and 90-100 spm. - Recovery: 1 minute active recovery at 10% PPO and about 50 spm. - Sets or repetitions: Repeated for 25 minutes. - Intensity: Vigorous-intensity intervals prescribed from PPO derived from a TBRS submaximal exercise test. - Session duration: 25-minute main set plus standardized warm-up and cool-down. - Frequency: 3 sessions/week. - Program length: 4 weeks. - Progression: Not explicitly reported beyond individualized PPO-based prescription. - MICT. - Modality: Total-body recumbent stepper. - Work intervals: Continuous exercise. - Sets or repetitions: 25 minutes continuous. - Intensity: 45%-65% PPO at 90-100 spm. - Session duration: 25-minute main set plus standardized warm-up and cool-down. - Frequency: 3 sessions/week. - Program length: 4 weeks. - Progression: Not explicitly reported beyond individualized PPO-based prescription. ## Outcomes ### Predicted VO2peak Status: improved Both groups improved from baseline, but HIIT was not superior to MICT. Between-group beta=-0.58, SE 0.93, p=0.54; HIIT +1.13 mL/kg/min (95% CI 0.05 to 2.21), p=0.04; MICT +1.58 (95% CI 0.18 to 2.97), p=0.03. ### Peripheral vascular function Status: mixed No significant between-group effect, but HIIT improved flow-mediated dilation within group in both stroke-affected and non-affected arms. Stroke-affected arm beta=0.48, SE 1.09, p=0.66; non-affected arm beta=0.42, SE 0.85, p=0.62. HIIT within-group changes: +1.43%, p=0.02 and +1.60%, p=0.04. ### Walking outcomes Status: improved No significant between-group differences; both groups improved fast gait speed and walking endurance, and MICT improved comfortable gait speed. Comfortable gait speed beta=-0.06, SE 0.04, p=0.19; fast gait speed beta=0.03, SE 0.04, p=0.53; 6-minute walk beta=9.04, SE 10.32, p=0.39. ### Treatment fidelity and adherence Status: improved Attendance was near complete and HIIT achieved vigorous-intensity heart rates during most prescribed intervals. Attendance 99.5% overall; HIIT achieved vigorous HR during 80.6% of prescribed high-intensity intervals; HIIT lactate higher than MICT by 0.735 mmol/L (95% CI 0.353 to 1.117), p<0.001. ### Safety Status: mixed Adverse events occurred, but no serious adverse events were study-related. 24 AEs among 17 participants; 6 possibly/definitely intervention-related; 1 hospitalization SAE unrelated. ## Practical Insights - In supervised chronic-stroke rehabilitation, a 1-minute on/1-minute active recovery HIIT format can be delivered with high adherence when prescribed from submaximal testing and monitored. - Early 4-week improvements in fitness and walking may depend on adequate aerobic dosing rather than interval format alone. - HIIT superiority claims should be avoided for short-term predicted VO2peak based on this trial. - Clinical HIIT safety evidence depends on screening, individualized dosing, continuous monitoring, and clinician oversight. ## Limitations - Modest sample size. - Preliminary efficacy design not powered for definitive comparison. - Single-site study. - Short 4-week intervention. - Predicted rather than directly measured VO2peak primary outcome. - No objective monitoring of outside physical activity. - No long-term maintenance assessment. - Chronic stroke population only. ## Safety And Adherence - No study-related serious adverse events occurred. - 17 participants had 24 adverse events: 10 in HIIT and 14 in MICT. - Six AEs were possibly or definitely related to the intervention. - Study-related AEs led to one dose reduction and three temporary pauses. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/41891032/) (pubmed) - [DOI](https://doi.org/10.64898/2026.03.17.26348646) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13015686/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.