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

Background: 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).

Aims: To assess the clinical effectiveness and safety of low-volume HIIT compared with moderate-intensity steady-state (MISS) exercise training for people with CAD.

Methods and results: 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 × 1 min intervals of vigorous exercise (>85% maximum capacity) interspersed with 1 min 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 (VO_{2 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, VO_{2 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.

Conclusions: 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.

Trial registration: ClinicalTrials.gov: NCT02784873. https://clinicaltrials.gov/ct2/show/NCT02784873.