Wright, H. E., Phinney, C. N., Hardcastle, S. G., McLellan, T. M., Larose, J., Boulay, P., & Kenny, G. P. (2013). Young versus older males’ thermoregulatory responses to exercise in humid heat under two air velocities. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 349.

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This study examined the effects of exercise in warm/humid heat under two different levels of air velocity that modified the level of evaporative cooling on the heat stress responses of young versus older adults. Young (~24.1 years; N = 10) and older (~59.1 years; N = 10) males matched for body-surface area and wearing work coveralls, performed four successive 15-minute cycling bouts (15 minutes rest) at a fixed rate of heat production (400 W) in humid hot conditions (35°C, 60% relative humidity) with 0.5 (Low) and 3.0 m/s (High) air velocity. Rectal temperature was measured continuously. Blood and urine were analyzed prior to exercise and the end of final recovery for hemoglobin, hematocrit, and Interleukin, and urine specific gravity.

Rectal temperature changes were similar between age groups under both air velocities. Plasma volume changes were similar between both groups. No age-related differences were seen for Interleukin. No age or condition differences in urine specific gravity were seen.

Implication. Young and older males show similar thermal strain and changes in hydration status following intermittent exercise in humid heat. High air-velocity reduced strain within both age groups.

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