We investigated whether single or combined methods of pre-cooling could affect high-intensity exercise performance in a hot environment. Seven male athletes were subjected to four experimental conditions for 30 min in a randomised order. The four experimental conditions were: 1) wearing a vest cooled to a temperature of 4 °C (Vest), 2) consuming a beverage cooled to a temperature of 4 °C (Beverage), 3) simultaneous usage of vest and consumption of beverage (Mix), and 4) the control trial without pre-cooling (CON). Following those experimental conditions, they exercised at a speed of 80% VO2max until exhaustion in the heat (38.1 ± 0.6 °C, 55.3 ± 0.3% RH). Heart rate (HR), rectal temperature (Tcore), skin temperature (Tskin), sweat loss (SL), urine specific gravity (USG), levels of sodium (Na+) and potassium (K+), rating of perceived exertion (RPE), thermal sensation (TS), and levels of blood lactic acid ([Bla]) were monitored. Performance was improved using the mixed pre-cooling strategy (648.43 ± 77.53 s, p = 0.016) compared to CON (509.14 ± 54.57 s). Tcore after pre-cooling was not different (Mix: 37.01 ± 0.27 °C, Vest: 37.19 ± 0.33 °C, Beverage: 37.03 ± 0.35 °C) in all cooling conditions compared to those of CON (37.31 ±0.29 °C). A similar Tcore values was achieved at exhaustion in all trials (from 38.10 °C to 39.00 °C). No difference in the level of USG was observed between the conditions. Our findings suggest that pre-cooling with a combination of cold vest usage and cold fluid intake can improve performance in the heat. Key Points Precooling strategies with 30 min independent or simultaneous precooling maneuvers could improve running performance of 80% VO2max in hot and humid climatic conditions compared with the control condition. Wearing a 4 °C vest might augment the capacity of heat dissipation by decreasing Tskin. Ingesting a 4 °C beverage might increase the capacity of heat storage and maintain homeostasis by reducing Tcore, HR and [Bla]. The mix method-precooling maneuver seems to be more effective than others by maintaining core-to-skin thermal gradient and fortifying heat storage to relieve thermophysiological strain.
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