Regional Surface Temperature Responses During a High Intensity Heat Acclimation Protocol

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0573 Mean skin temperature (MST) response to heat acclimation is vital to thermal regulation given the skin's role as an interface between the body's core and the environment. Quantification of MST must account for regional differences as well as the temperature range across the body surface. Previous studies have generally relied upon single site contact measurements of regional skin temperatures. However, contact measures may alter the skin temperature at site of contact, whereas single site measures may not accurately represent the range of temperatures that exist within a region. PURPOSE: To assess effect of age on regional surface thermal and sweating responses among highly fit males across a 14 day high intensity heat acclimation protocol. METHODS: Nine younger (20.4 ± 0.8 years) and eight older (45.8 ± 1.9 years) aerobically fit males ran daily for 30 minutes at 75% VO2max in a hot, humid (35°C, 35% RH) environment. Core temperature (Tc) and heart rate (HR) were monitored continuously; perceived exertion (RPE), thermal sensation (TS) and sweat volume were measured during each trial. Plasma volume, MST and regional surface (RST) temperatures and core to skin thermal gradient were measured across the protocol. MST and RST measures were obtained from infrared thermographic imaging. RESULTS: VO2max did not significantly differ across protocol or between groups (55.2 ± 2.4 older vs. 57.1 ± 1.3 ml.kg−1.min−1 younger pre-acclimation, 56.1 ± 2.3 older vs. 58.5 ± 1.2 ml.kg−1.min−1 younger post-acclimation). Tc, MST and RST significantly decreased across protocol for both groups (P < 0.05). Older runners demonstrated significantly lower post-trial MST and RST than younger participants. Core to skin thermal gradient significantly increased across time; older participants demonstrated a significantly greater gradient than younger runners on day 1. Post-trial forehead and torso RST were significantly greater than upper and lower limb RST for both groups. CONCLUSIONS: Infrared thermographic imaging provided an accurate surface temperature measure that accounted for the range of temperatures existing within each region. Decreases in Tc, MST and RST indicate an improved heat transfer capacity given consistent metabolic heat production resulting from a set workload across protocol. Despite MST and RST differences between groups, younger and older participants responded similarly across the protocol. This suggests that the highly fit older male participants improved their heat transfer capacities to a similar extent as their younger counterparts. Supported by Gatorade Sports Science Institute.