Abstract
Rapid cooling techniques are essential for populations that are active in the heat. In attempt to reduce overheating, the vasomotor reflex increases blood flow to the skin for radiative heat loss, causing peripheral vasodilation. Cooling of the extremities can be a strategy to reduce core temperature (Tc) due to their large surface area and the increased blood flow during elevations of Tc. PURPOSE: To examine the effects of four hand-cooling methods on physiological strain following two interval blocks of cycling in the heat. METHODS: Twelve participants [mean ± SD; age, 24 ± 4 years; maximal oxygen consumption; 44.5 ± 6.4 ml/kg/min; body mass, 75.7 ± 8.2 kg; height, 177.3 ± 8.4 cm] performed two 40-min blocks of cycling at 6 Watts per kilogram of body mass (W/kg) to 15 W/kg in the heat (36 °C, 30 °C relative humidity). Metabolic heat production (Hprod) was used to prescribe this exercise intensity. Each 40-min exercise block was followed by 20-min of cooling. Participants completed four trials on four separate days that included four different cooling modalities during the rest block: 1) hand mist-fan cooling (FAN), 2) forearm ice-water immersion (IMM), 3) forearm ice-towel cooling (TOW), and 4) passive cooling (PAS). Heart rate (HR) and rectal temperature (Tc) were measured throughout each trial. Repeated measures analysis of variance (ANOVA) tests were used to identify differences between experimental groups. Statistical significance was set at p ≤ 0.05. RESULTS: There were no differences between the three cooling modalities compared to passive cooling for Tc and HR. There were no significant differences between HR and Tc at any time points from block 1 and 2 of exercise. CONCLUSION: The cooling modalities FAN, IMM, and TOW provided no additional cooling benefits on Tc and HR compared to PAS. Populations that are exposed to environmental heat-stress should consider alternative cooling strategies or mixed methods cooling modalities that will improve heat loss and attenuate Tc.
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