The purpose of the study was to examine the effects of sprint interval training (SIT) and moderate-intensity continuous cycle training (MICT), with equal estimated energy expenditure during training on body composition and aerobic capacity. Body composition measured via dual-energy x-ray absorptiometry and aerobic capacity were assessed following 6 weeks of training in previously inactive overweight/obese young women (n = 52; age 20.4 +/- 1.5 years; body mass index 30.3 +/- 4.5 kg/m2, 67.3% white). Training was performed in a group-exercise format that mimicked cycling classes offered by commercial fitness facilities, and included 3 weekly sessions of either 30-s 'all-out' sprints followed by 4 min of active recovery (SIT), or continuous cycling at 60% to 70% heart rate reserve to expend a similar amount of energy. Participants were randomized to SIT or MICT, attended a similar number of sessions (15.0 +/- 1.5 sessions versus 15.8 +/- 1.9 sessions, p = 0.097) and expended a similar amount of energy (541.8 +/- 104.6 kJ/session versus 553.5 +/- 138.1 kJ/session, p = 0.250). Without significant changes in body mass (p > 0.05), greater relative reductions occurred in SIT than in MICT in total fat mass (3.6% +/- 5.6% versus 0.6% +/- 3.9%, p = 0.007), and android fat mass (6.6% +/- 6.9% versus 0.7% +/- 6.5%, p = 0.002). Aerobic capacity (mL/kg/min) increased significantly following both interventions (p < 0.05), but the relative increase was 2-fold greater in SIT than in MICT (14.09% +/- 10.31% versus 7.06% +/- 7.81%, p < 0.001). In conclusion, sprint-interval cycling reduces adiposity and increases aerobic capacity more than continuous moderate-intensity cycling of equal estimated energy expenditure in overweight/obese young women.

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