Conductive and evaporative precooling lowers mean skin temperature and improves time trial performance in the heat

Self-paced endurance performance is compromised by moderate-to-high ambient temperatures that are evident in many competitive settings. It has become common place to implement precooling prior to competition in an attempt to alleviate perceived thermal load and performance decline. The present study aimed to investigate precooling incorporating different cooling avenues via either evaporative cooling alone or in combination with conductive cooling on cycling time trial performance. Ten trained male cyclists completed a time trial on three occasions in hot (35 °C) ambient conditions with the cooling garment prepared by (a) immersion in water (COOL, evaporative); (b) immersion in water and frozen (COLD, evaporative and conductive); or (c) no precooling (CONT). COLD improved time trial performance by 5.8% and 2.6% vs CONT and COOL, respectively (both P < 0.05). Power output was 4.5% higher for COLD vs CONT (P < 0.05). Mean skin temperature was lower at the onset of the time trial following COLD compared with COOL and CONT (both P < 0.05) and lasted for the first 20% of the time trial. Thermal sensation was perceived cooler following COOL and COLD. The combination of evaporative and conductive cooling (COLD) had the greatest benefit to performance, which is suggested to be driven by reduced skin temperature following cooling.