Soccer half-time strategy influences thermoregulation and endurance performance

Aim. In the first 15 min of the second half in professional soccer, there is a reduction of high intensity distance covered and a high incidence of injuries sustained, possibly due to a reduction in body temperature during the half-time (HT). The aim of this study was to investigate the effect of active and passive re-warm-up strategies on cardiovascular (heart rate, HR) and thermoregulatory stress, and second-half soccer-specific endurance performance (SSEP). Methods. Seven professional players performed two intermittent field tests of 16.5 min duration, with a 15 min HT. On separate, randomised occasions, 4 trials were completed during which different HT strategies were undertaken between minutes 7 and 14 of the HT interval. Two passive trials were completed: rest control trial (CON), or players were immersed to the gluteal fold in a hot bath (∼40 °C-passive heating, PH); in the active trials, players performed at 70% maximum HR, either steady-state non-specific active heating (cycling, NSAH) or intermittent soccer-specific active heating (sprinting repeatedly, SSAH). HR and core temperature (T_c) were measured every 5 min, and body weight was recorded pre and post each trial. Results. Active re-warm-up strategies maintained SSEP in the second period with respect to CON (P<0.01), whereas PH did not reduce the decrement in performance (P>0.05). Active heating strategies increased HR during HT in comparison to CON, whereas PH did not. During the HT period in the CON trial, T_c decreased by 0.97±0.29 °C, PH and SSAH trials did not attenuate this decrease (P>0.01), whereas NSAH increased T_c in respect to CON (P<0.01). These differences in HR and T_c between re-warm-up strategies during HT were not apparent at the end of the trials. Conclusion. Active re-warm-up strategies during HT attenuated the decrement in second-half SSEP that was observed during passive trials.