PURPOSE: Excess post-exercise energy expenditure (EPEEE) refers to sustained elevation in energy expenditure above resting levels after exercise. This study compared the effect of morning (AM) and evening (PM) resistance exercise on EPEEE, with and without circadian rhythm (CR) adjustments.
METHODS: In this randomized crossover study, 13 men with prior resistance training experience performed six resistance exercises, each with three sets of 10 repetitions at 60% one-repetition maximum, in separate AM and PM sessions. Resting energy expenditure (REE) and post-exercise energy expenditure (PEEE) were measured via exhaled gas analysis; EPEEE was calculated by subtracting REE from PEEE. CR-adjusted values were calculated using a sinusoidal model of energy expenditure across the day to derive REE-CR, PEEE-CR, and EPEEE-CR.
RESULTS: REE did not differ significantly between AM and PM. Mean REE-CR values for AM and PM were similar. PEEE-CR in AM (194.4 ± 27.5 kcal/2 h) was significantly higher than that in PM (183.5 ± 32.2 kcal/2 h; P = 0.030), though insignificant in unadjusted PEEE. EPEEE was significantly higher in AM (49.8 ± 21.0 kcal/2 h) than in PM (30.1 ± 18.8 kcal/2 h; P = 0.049). CR adjustment attenuated EPEEE enhancement at AM; moreover, the difference in EPEEE-CR between AM and PM was no longer significant (AM: 47.3 ± 20.8 kcal/2 h; PM: 31.4 ± 18.9 kcal/2 h; P = 0.100).
CONCLUSION: Compared to evening exercise, morning resistance exercise increases EPEEE; however, this difference diminishes when CRs are considered. These findings offer practical implications for optimizing resistance exercise prescriptions aimed at improving metabolism and cardiometabolic health.
