2019 Volume 49 Issue 5 Pages 191-200
Objectives: This study aimed to investigate the substrate metabolism response to moderateand high-intensity equicaloric exercises in endurance-trained men.
Methods: Ten male endurance-trained runners (mean ± standard error: age, 22 ± 1 years; body mass index, 19.3 ± 0.7 kg/m2; ⩒O2max, 64.1 ± 2.1 mL/kg/min) performed a graded exercise test on a treadmill to determine the exercise intensity at which elicits maximal fat oxidation (Fatmax) and subsequently completed two equicaloric exercises (53 min at Fatmax and 30 min at 65％⩒O2max). Substrate oxidation rates during exercise and 2-h post-exercise recovery period were determined using indirect calorimetry. Blood samples were collected before exercise; immediately post-exercise; and at 30 min, 1 h, and 2 h post-exercise to determine plasma noradrenaline, serum growth hormone (GH), and free fatty acid (FFA) concentrations.
Results: Mean Fatmax was observed at 37.3 ± 4.6 ％⩒O2max. Fat oxidation volume during exercise was significantly higher in the Fatmax trial than in the 65％⩒O2max trial (15.2 ± 1.5 g vs 8.5 ± 0.7 g, P ＜ 0.01). No significant difference in fat oxidation occurred in the post-exercise recovery period. Serum GH and plasma noradrenaline concentrations were higher at 65％⩒O2max than at Fatmax immediately post-exercise (P ＜ 0.05). However, there was no difference in serum FFA levels between exercise intensities.
Conclusions: Exercise at Fatmax oxidized more fat than exercise at 65％⩒O2max when matched for energy expenditure during exercise in endurance-trained men.