The influence of thermal factors on postexercise haemodynamics in trained and untrained men

Abstract

Previous work suggests that the cardiovascular mechanisms underlying the postexercise reduction in mean arterial pressure (MAP) differ between exercise‐trained and untrained men. However, these studies compared responses based on the same percentage of peak oxygen consumption (VO2peak) resulting in different rates of heat production during exercise. Thus, we evaluated if exercise‐induced differences in the requirement for heat loss, and therefore sweat loss, may influence postexercise haemodynamics. Twelve trained (T60) (VO2peak, 64 ± 4 mL/kg/min) and twelve untrained (UT60) (VO2peak, 49 ± 3 mL/kg/min) males, individually matched for body surface area, cycled for 60 min at 60% of VO2peak­. On a separate day the untrained group performed an additional 60 min of cycling at the same heat production as their trained match in T60 (UTMatch). Sweat loss was assessed by change in body weight (ΔBW). MAP and cardiac output (CO) were measured at baseline and every 10 min during 60 min of postexercise recovery. ΔBW was similar between T60 and UT­Match (T60: ‐1.32 ± 0.36 kg; UTMatch: ‐1.32 ± 0.32 kg) and greater in these conditions relative to UT60 (‐0.95 ± 0.13 kg; both P < 0.05). Further, MAP was ~5 mmHg below baseline following 20 min of recovery in each condition (all P < 0.05). Postexercise CO was ~7% below baseline in T60 (P < 0.05) whereas it was elevated relative to T60 (both P < 0.05) and similar to baseline (both P > 0.05) in UT60 and UTMatch. We show that the differing mechanisms between trained and untrained males underlying the postexercise reduction in MAP are not the result of differences in exercise‐induced heat load and therefore fluid loss. Support: Natural Sciences and Engineering Research Council of Canada.