Hannan AL, et al. - This meta-analysis was performed to examine cardiorespiratory fitness changes resulting from high-intensity interval training (HIIT) vs moderate-intensity continuous training (MICT) within the cardiac population and to collate adverse events. Compared to MICT, HIIT was superior in improving cardiorespiratory fitness in participants of cardiac rehabilitation (CR). Improvements in cardiorespiratory fitness were significant for CR programs of >6-week duration. For patients with coronary artery disease, programs of 7–12 weeks’ duration resulted in the largest improvements in cardiorespiratory fitness. For CR participants, HIIT seemed to be as safe as MICT.