High-intensity interval training in cardiac rehabilitation: a multi-centre randomized controlled trial.

There is a lack of international consensus regarding the prescription of high-intensity interval training (HIIT) for people with coronary artery disease (CAD) attending cardiac rehabilitation (CR). The aim of this study was therefore to assess the clinical effectiveness and safety of low-volume HIIT compared with moderate-intensity steady-state (MISS) exercise training for people with CAD. We conducted a multi-centre RCT, recruiting 382 patients from 6 outpatient CR centres. Participants were randomized to twice-weekly HIIT (n = 187) or MISS (n = 195) for 8 weeks. HIIT consisted of 10 one-minute intervals of vigorous exercise (>85% maximum capacity) interspersed with one-minute periods of recovery. MISS was 20–40 min of moderate-intensity continuous exercise (60–80% maximum capacity). The primary outcome was the change in cardiorespiratory fitness [peak oxygen uptake (VO2 peak)] at 8 week follow-up. Secondary outcomes included cardiovascular disease risk markers, cardiac structure and function, adverse events, and health-related quality of life. At 8 weeks, VO2 peak improved more with HIIT (2.37 mL.kg−1.min−1; SD, 3.11) compared with MISS (1.32 mL.kg−1.min−1; SD, 2.66). After adjusting for age, sex, and study site, the difference between arms was 1.04 mL.kg−1.min−1 (95% CI, 0.38 to 1.69; P = 0.002). Only one serious adverse event was possibly related to HIIT. The study therefore concluded that, in stable CAD, low-volume HIIT improved cardiorespiratory fitness more than MISS by a clinically meaningful margin. Low-volume HIIT is a safe, well-tolerated, and clinically effective intervention that produces short-term improvement in cardiorespiratory fitness. It should be considered by all CR programmes as an adjunct or alternative to MISS. This trial was registered on ClinicalTrials.gov: NCT02784873, https://clinicaltrials.gov/ct2/show/NCT0278487