Morning versus evening power output and repeated-sprint ability

摘要

We investigated the effect of time-of-day on both maximal sprint power and repeated-sprint ability (RSA). Nine volunteers (22 +/- 4 yrs) performed a RSA test both in the morning ( 07: 00 to 09: 00 h) and evening ( 17: 00 to 19: 00 h) on different days in a random order. The RSA cycle test consisted of five, 6 sec maximal sprints interspersed by 24 sec of passive recovery. Both blood lactate concentration and heart rate were higher in the evening than morning RSA ( lactate values post exercise: 13 +/- 3 versus 11 +/- 3 mmol/L-1, p <0.05). The peak power developed during the first sprint was higher in the evening than morning (958 +/- 112 vs. 915 +/- 133 W, p< 0.05), but this difference was not apparent in subsequent sprints, leading to a higher power decrement across the 5 x 6 sec test in the evening (11 +/- 2 vs. 7 +/- 3%, p< 0.05). Both the total work during the RSA cycle test and the power developed during bouts 2 to 5 failed to be influenced by time-of-day. This suggests that the beneficial effect of time-of-day may be limited to a single expression of muscular power and fails to advantage performance during repeated sprints.