Effect of Two Doses of Interval Training on Maximal Fat Oxidation in Sedentary Women

Introduction: The primary aim of the current study was to determine the effect of two doses of chronic high-intensity interval training (HIT) on changes in maximal fat oxidation (MFO) and body composition. Methods: Sedentary women (N = 23, age and (V) over dotO(2max) = 24.2 +/- 6.2 yr and 30.3 +/- 5.2 mL.kg(-1).min(-1), respectively) completed either high (HI) (80%-90% maximal workload) or moderate (MOD) intensity (60%-80% maximal workload) HIT on a cycle ergometer 3 d.wk(-1) for 12 wk consisting of 6-10 sixty-second bouts interspersed with active recovery. Seven women of similar age and fitness level served as controls. Every 3 wk, substrate oxidation was assessed during progressive exercise via indirect calorimetry to determine MFO and minimum fat oxidation, and body composition was assessed every 6 wk. Repeated-measures ANOVA was used to examine changes in substrate oxidation in response to training, with training group used as a between-subjects variable. Results: Results revealed improved MFO (P = 0.04, 19%-25%) and minimum fat oxidation (P = 0.001, 22-24 W) in response to HIT, yet the magnitude of improvement was similar (P > 0.05) between training paradigms. No change (P > 0.05) in body weight, percent body fat, or waist-hip circumference was revealed with training. Conclusion: These data suggest that 12 wk of either moderate or more strenuous interval training similarly enhance fat oxidation in sedentary women but do not alter body weight or body composition.