Despite the established therapeutic potential of moderate-intensity to vigorous-intensity physical activity, 31.1% of the adult worldwide (43% US population) fails to meet the minimum physical activity guidelines. The WHO 1 and the American College of Sports Medicine (ACSM) 2 recommend at least 150 min of moderate-intensity physical activity (40–60% maximum oxygen uptake (VO 2 max) 3) or 75 min of vigorous-intensity physical activity (60–85% VO 2 max) per week for healthy adults to maintain or improve health. Current evidence suggests that ST-HIIT and LT-HIIT can increase VO 2 max and improve some cardiometabolic risk factors in overweight/obese populations. In normal weight populations, ST-HIIT and LT-HIIT significantly improved VO 2 max, but no other significant effects were observed. HIIT demonstrated no effect on insulin, lipid profile, C reactive protein or interleukin 6 in overweight/obese populations. Outcomes with at least 5 effect sizes were synthesised using a random-effects meta-analysis of the standardised mean difference (SMD) in cardiometabolic health markers (baseline to postintervention) using Review Manager 5.3. Studies were classified by intervention duration and body mass index classification. Sixty-five intervention studies were included for review and the methodological quality of included studies was assessed using the Downs and Black score.

A systematic search (PubMed) examining HIIT and cardiometabolic health markers was completed on 15 October 2015. The current review clarifies the cardiometabolic health effects of high-intensity interval training (HIIT) in adults.

High intensity workouts