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

<p> <strong>Background</strong></p> <p>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).</p> <p><strong>Aims</strong></p> <p>To assess the clinical effectiveness and safety of low-volume HIIT compared with moderate-intensity steady-state (MISS) exercise training for people with CAD.</p> <p><strong>Methods and results</strong></p> <p>We conducted a multi-centre RCT, recruiting 382 patients from 6 outpatient CR centres. Participants were randomized to twice-weekly HIIT (<em>n</em> = 187) or MISS (<em>n</em> = 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 (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; <em>P</em> = 0.002). Only one serious adverse event was possibly related to HIIT.</p> <p><strong>Conclusions</strong></p> <p>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.</p>