High-intensity interval training within cardiac rehabilitation: a multi-center randomized controlled trial.

High-intensity interval training (HIIT) HIIT consists of 6 weeks x 2 sessions/week (12 sessions), involving stationary cycling of 15-20 repetitions × 30-second intervals at 85-90% HRmax (RPE ~14-17), interspersed with 30-second active recovery. Each session will begin with a 10-minute moderate-intensity warm-up at ~65% HRmax and ended with a 5-minute active recovery cool-down. For the first 3-weeks of training, all patients will complete 15 repetitions per session (including 2 passive rests for BP measurement – after the 5th and 10th repetition); in the final 3-weeks of training, patients will complete 20 repetitions per session (including 1 passive rest – after the 10th repetition). The passive rest periods will be ~30-seconds or until BP measurement has been accurately recorded. Workloads are determined by the clinical staff (physiotherapists and exercise physiologists) to maintain the target HR (and/or RPE) range for the 5- or 10-repetition block (before a passive rest for BP measurement). HR and RPE will be recorded in the last 5 seconds of every 5th work interval. HR and BP will be monitored during the cool-down period to ensure patient safety. The total time commitment for each HIIT session is 30 minutes (for 15 total repetitions) to 35 minutes (for 20 total repetitions), equating to mean across all sessions 32.5 minutes.