Active warm-up and time-of-day effects on repeated-sprint performance and post-exercise recovery

Purpose This study investigated the effects of both an active warm-up and the time-of-day variation on repeated-sprint performance. A second objective was to compare the post-exercise recovery between the experimental conditions. Methods Eleven male participants performed ten maximal cycling sprints (6 s each, with a 30-s interval between them) in the morning and late afternoon, either after a warm-up or control condition. The warm-up consisted of cycling for 10 min at 50% of the peak aerobic power. Results Rest measurements of rectal, muscle, and skin temperatures were higher in the afternoon compared to the morning ( p < 0.05), with no significant differences in heart rate ( p = 0.079) and blood lactate concentration ( p = 0.300). Warm-up increased muscle temperature, heart rate, and lactate, and reduced skin temperature (all p < 0.001), though no significant differences were observed for rectal temperature ( p = 0.410). The number of revolutions ( p = 0.034, η p 2 = 0.375), peak ( p = 0.034, η p 2 = 0.375), and mean ( p = 0.037, η p 2 = 0.365) power of the first sprint (not the average of ten sprints) were higher in the afternoon compared to the morning, regardless of warm-up. However, beneficial performance effects of warming up were evident for the first ( p < 0.001) and the average of ten sprints ( p < 0.05), regardless of time of day. More remarkable changes during the 60-min post-exercise were observed for rectal temperature ( p = 0.005) and heart rate ( p = 0.010) in the afternoon than in the morning. Conclusion Warming-up and time-of-day effects in enhancing muscular power are independent. Although warm-up ensured further beneficial effects on performance than the time-of-day variation, a faster post-exercise recovery was observed in the late afternoon.