Effect of a 1-hour single bout of moderate-intensity exercise on fat oxidation kinetics.

Abstract The present study aimed to examine the effects of a prior 1-hour continuous exercise bout (CONT) at an intensity (Fat max ) that elicits the maximal fat oxidation (MFO) on the fat oxidation kinetics during a subsequent submaximal incremental test (IncrC). Twenty moderately trained subjects (9 men and 11 women) performed a graded test on a treadmill (Incr), with 3-minute stages and 1-km·h −1 increments. Fat oxidation was measured using indirect calorimetry and plotted as a function of exercise intensity. A mathematical model (SIN) including 3 independent variables ( dilatation , symmetry , and translation ) was used to characterize the shape of fat oxidation kinetics and to determine Fat max and MFO. On a second visit, the subjects performed CONT at Fat max followed by IncrC. After CONT performed at 57% ± 3% (means ± SE) maximal oxygen uptake (Vo 2max ), the respiratory exchange ratio during IncrC was lower at every stage compared with Incr ( P max (56.4% ± 2.3% vs 51.5% ± 2.4% Vo 2max , P = .013), MFO (0.50 ± 0.03 vs 0.40 ± 0.03 g·min −1 , P 2max ( P dilatation and translation were not significantly different ( P > .05), whereas symmetry tended to be greater in IncrC ( P = .096). This study showed that the prior 1-hour continuous moderate-intensity exercise bout increased Fat max , MFO, and fat oxidation rates over a wide range of intensities during the postexercise incremental test. Moreover, the shape of the postexercise fat oxidation kinetics tended to have a rightward asymmetry.