Effects of Mixed Pre-cooling on Male Middle-and Long-Distance Runner’s Thermoregulation and Aerobic Endurance Performance in the Heat

To investigate the effects of mixed pre-cooling on male middle-and long-distance runner's thermoregulation and endurance performance in the heat. Ten trained male runners were randomly divided into either a control group(PC, n=5) or a mixed pre-cooling group(MP, n=5). A 20 min pre-cooling program was conducted after a 10 min standard warm up, i. e., the PC group ingested 1.5 g/kg sports drinks(25 ℃) at every 5 min; the MP group ingested 1.5 g/kg sports drinks(5 ℃) at every 5 min, and they were cooled by using the cooling gloves called CoreControl^TM at the same time. Each participant performed a 5 km time trial(5 km TT) in the heat(30~31 ℃, 57% relative humidity) after pre-cooling. During pre-cooling, the interactive effects of pre-cooling and time on gastrointestinal temperature(Tgi), body temperature(Tb) and physiological strain index(PSI) were significant(P<0.001,ES=2.96; P<0.001, ES=2.41; P=0.001, ES=1.6), and the Tgi and PSI were significantly different between PC and MP at the end of pre-cooling(P=0.003, P=0.001). No significant interactive effects of pre-cooling and time significance on skin temperature(Tsk),heat storage(HS), and heart rate(HR) were observed(P=0.975, P=0.263, P=0.071). During the 5 km TT, the interactive effects of pre-cooling and time on Tgi, Tsk, Tb, HS, PSI, HR were not significant(P>0.05), and the main effects of pre-cooling on Tgi and PSI was significant(P=0.028, ES=1.68; P=0.013, ES=2.11). There was no significant difference in sweat rate between MP and PC group(P=0.63). There was a significant difference in the 5 km TT between MP and PC group(P=0.035). Cold drink combined with hand cooling can reduce the core temperature and physiological strain index before exercise in the heat, it can also delay the increase of core temperature and physiological strain index during the 5 km TT which resulted in the improvement of the aerobic endurance performance.