Controlling rectal and muscle temperatures: Can we offset diurnal variation in repeated sprint performance?

摘要

The present study investigated whether increasing morning rectal temperatures (T-rec) to resting.evening levels, or decreasing evening T-rec or muscle (T-m) temperatures to morning values, would influence repeated sprint (RS) performance in a causal manner. Twelve trained males underwent five sessions [age (mean +/- SD) 21.8 +/- 2.6yr, peak oxygen uptake (VO2 peak) 60.6 +/- 4.6mL kg min(-1), stature 1.78 +/- 0.07m and body mass 76.0 +/- 6.3kg]. These included a control morning (M, 07:30h) and evening (E, 17:30h) session (5-min warm-up), and three further sessions consisting of a warm-up morning trial (M-E, on a motorised treadmill) until T-rec reached evening levels; and two cool-down evening trials (in 16-17 degrees C water) until T-rec (E-Mrec) or T-m (E-Mmuscle) values reached morning temperatures, respectively. All sessions included a 3 x 3-s task-specific warm-up followed by 10 x 3-s RS with 30-s recoveries performed on a non-motorised treadmill. T-rec and T-m measurements were taken at the start of the protocol and following the warm-up or cool-down period. Values for T-rec and T-m were higher in the evening compared to morning values (0.45 degrees C and 0.57 degrees C, P<0.05). RS performance was lower in the M for distance covered (DC), average power (AP) and average velocity (AV) (9-10%, P<0.05). Pre-cooling T-rec and T-m in the evening reduced RS performance to levels observed in the morning (P<0.05). However, an active warm-up resulted in no changes in morning RS performance. Diurnal variation in T-rec and T-m is not wholly accountable for time-of-day oscillations in RS performance on a non-motorised treadmill; the exact mechanism(s) for a causal link between central temperature and human performance are still unclear and require more research.