Endurance exercises such as a marathon consume large quantities of energy. It is essential to depend on fat oxidation for saving body carbohydrate （CHO） fuel sources. Fat oxidation enhances the decline of CHO fuel sources. This study was conducted to estimate energy metabolism during endurance running after high-intensity running. Eight male distance runners （V4 O2max: 68.7±4.5 ml/kg/min） were recruited for this study. The runners underwent three endurance treadmill running tests. After the warming-up running, they undertook high-intensity running （1.5km Test: 1.5km-run for 95% of V4 O2max; Interval Test: 200m-sprint×5 for 110% of V4 O2max） before endurance running （90% of Lactate Threshold）. In addition, they did constant endurance running （90%LT） till the end as a control test. Results revealed no significant differences in energy consumption among the three tests. Both initial high-intensity running tests showed a lower respiratory gas exchange ratio was maintained during endurance running than in Control Test. These results suggest that endurance running with pre high-intensity running was higher dependent on fat oxidation than constant endurance running.
