Background: The relationship between the frequency of high-intensity interval training (HIIT) and the resultant adaptations is largely unclear.
Purpose: This study compared the effects of different frequencies of HIIT with those of moderate-intensity continuous training (MICT) on body composition in overweight or obese adults.
Methods: Fifty-six overweight or obese (body mass index = 26.4 ± 2.9) men between 18 and 30 yr old (age = 22.8 ± 3.1 yr) were randomly assigned to the following groups: no-intervention control (CON; n = 14), MICT performed thrice weekly (MICT×3/wk; n = 9), HIIT performed thrice weekly (HIIT×3/wk; n = 14), HIIT performed twice weekly (HIIT×2/wk; n = 10), and HIIT performed once weekly (HIIT×1/wk; n = 9). Each HIIT session consisted of 12 × 1-min bouts at 90% heart rate reserve, interspersed with 11 × 1-min bouts at 70% heart rate reserve. Aerobic capacity, body composition, resting heart rate, vascular function, insulin resistance, and biomarkers of metabolic syndrome risk factor were examined at baseline, after 4 wk, and after 8 wk of intervention.
Results: Aerobic capacity and percent fat-free mass significantly increased in all exercise groups compared with those in the CON group (CON vs all exercise groups, P < 0.05), whereas body fat mass and systolic blood pressure significantly decreased after 8 wk of intervention in all exercise groups compared with those in the CON group (CON vs all exercise groups, P < 0.05). Body fat mass significantly decreased after 4 wk in all HIIT groups compared with those in the CON group (CON vs all HIIT groups, P < 0.05) but not in the MICT×3/wk group.
Conclusion: These novel results demonstrated that performing HIIT once weekly, even with a lower weekly volume of exercise, improved cardiorespiratory fitness, body composition, and blood pressure in overweight/obese adults. Low-frequency HIIT might be a feasible and effective strategy for the prescription of an initial exercise program for inactive, overweight, or obese young men.