LAUSR

In humans, elevated body temperatures can markedly increase the ventilatory response to exercise. However, the impact of changing the effective body surface area for sweat evaporation on such responses is unclear. Ten healthy adults (9 Male, 1 Female) performed eight exercise trials cycling at 6 W/kg of metabolic heat production for 60 minutes. Four conditions were used where the effective body surface area for sweat evaporation (BSAeff) corresponded to 100, 80, 60, and 40% of BSA using vapor impermeable material. Four trials (one at each BSAeff) were performed at 25°C air temperature, and four trials (one at each BSAeff) at 40°C air temperature, each with 20% humidity. The slope of the relation between minute ventilation and carbon dioxide elimination (V̇E/V̇CO2 slope) assessed the ventilatory response. At 25°C, the V̇E/V̇CO2 slope was elevated by 1.9 and 2.6 units when decreasing BSAeff from 100 to 80 and to 40% (ps = 0.033 and 0.004, respectively). At 40°C, V̇E/V̇CO2 slope was` elevated by 3.3 and 4.7 units, when decreasing BSAeff from 100 to 60 and to 40% (ps = 0.016 and < 0.001, respectively). Linear regression analyses using group average data from each condition demonstrated that end-exercise mean body temperature (integration of core and mean skin temperatures) was better associated with the end-exercise ventilatory response, compared with core temperature alone. Overall, we show that impeding regional sweat evaporation increases the ventilatory response to exercise in temperate and hot environmental conditions, and the effect is mediated primarily by increases in mean body temperature.