Purpose: The aim of this study was to examine whether lipid oxidation predominates during 3 h of postexercise recovery in high-intensity interval exercise as compared with moderate-intensity continuous exercise on a cycle ergometer in fit young men (n = 12; 24.6 ± 0.6 yr).
Methods: The energy substrate partitioning was evaluated during and after high-intensity submaximal interval exercise (INT, 1-min intervals at 80% of maximal aerobic power output [W˙max] with an intervening 1 min of active recovery at 40% W˙max) and 60-min moderate-intensity continuous exercise at 45% of maximal oxygen uptake (C45%) as well as a time-matched resting control trial (CON). Exercise bouts were matched for mechanical work output.
Results: During exercise, a significantly greater contribution of CHO and a lower contribution of lipid to energy expenditure were found in INT (512.7 ± 26.6 and 41.0 ± 14.0 kcal, respectively) than in C45% (406.3 ± 21.2 and 170.3 ± 24.0 kcal, respectively; P < 0.001) despite similar overall energy expenditure in both exercise trials (P = 0.13). During recovery, there were no significant differences between INT and C45% in substrate turnover and oxidation (P > 0.05). On the other hand, the mean contribution of lipids to energy yield was significantly higher after exercise trials (C45% = 61.3 ± 4.2 kcal; INT = 66.7 ± 4.7 kcal) than after CON (51.5 ± 3.4 kcal; P < 0.05).
Conclusions: These findings show that lipid oxidation during postexercise recovery was increased by a similar amount on two isoenergetic exercise bouts of different forms and intensities compared with the time-matched no-exercise control trial.