Vol. 2, Issue 2, Part A (2025)

Background: High-intensity interval training (HIIT) has emerged as a time-efficient alternative to moderate-intensity continuous training (MICT) within cardiac rehabilitation, but data specific to post-coronary artery bypass grafting (CABG) patients remain limited. This study compared the effects of a HIIT-centred versus MICT-based phase II cardiac rehabilitation programme on functional capacity and health-related quality of life (HRQol) in stable post-CABG patients.

Methods: In this single-centre, parallel-group randomized controlled trial, 120 adults 4-8 weeks post-isolated CABG were allocated to either supervised HIIT (n=60) or MICT (n=60) for 12 weeks (three sessions/week) as part of comprehensive cardiac rehabilitation. The HIIT protocol comprised 4 × 4-minute intervals at 85-95% heart rate reserve (HRR) interspersed with 3-minute active recovery at 60-70% HRR, while MICT involved continuous exercise at 60-70% HRR for 30-40 minutes. Primary outcomes were changes in peak oxygen uptake (VO₂peak) and six-minute walk test (6MWT) distance from baseline to 12 weeks. Secondary outcomes included changes in HRQoL (MacNew questionnaire and SF-36), resting haemodynamic, and safety events. Analyses were performed on an intention-to-treat basis.

Results: Baseline characteristics were similar between groups. Exercise adherence was high and comparable. Both groups showed significant within-group improvements in VO₂peak and 6MWT distance, but gains were greater with HIIT. Mean VO₂peak increased by 4.2±2.1 mL·kg⁻¹·min⁻¹ in the HIIT group versus 2.3±1.9 mL·kg⁻¹·min⁻¹ in the MICT group (between-group difference 1.9 mL·kg⁻¹·min⁻¹; 95% CI 1.2-2.6; p<0.001). Mean 6MWT distance improved by 72±38 m (HIIT) and 44±34 m (MICT) (between-group difference 28 m; 95% CI 15-41; p<0.001). HIIT also produced larger improvements in MacNew global score and SF-36 physical functioning and vitality domains. No major adverse cardiovascular events occurred in either group; minor, self-limited events were infrequent and similar between arms.

Conclusion: In clinically stable post-CABG patients, a 12-week supervised HIIT programme within phase II cardiac rehabilitation yields superior and clinically meaningful improvements in functional capacity and HRQoL compared with conventional MICT, without increasing adverse events. HIIT represents a safe, effective, and practical training option that could be routinely offered to suitable post-CABG patients in contemporary cardiac rehabilitation practice.