Fluid replacement and heat stress during exercise alter post-exercise cardiac haemodynamics in endurance exercise-trained men

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Blackwell Science Inc

RESUMO

It has been reported that endurance exercise-trained men have decreases in cardiac output with no change in systemic vascular conductance during post-exercise hypotension, which differs from sedentary and normally active populations. As inadequate hydration may explain these differences, we tested the hypothesis that fluid replacement prevents this post-exercise fall in cardiac output, and further, exercise in a warm environment would cause greater decreases in cardiac output. We studied 14 trained men ( 4.66 ± 0.62 l min−1) before and to 90 min after cycling at 60% for 60 min under three conditions: Control (no water was consumed during exercise in a thermoneutral environment), Fluid (water was consumed to match sweat loss during exercise in a thermoneutral environment) and Warm (no water was consumed during exercise in a warm environment). Arterial pressure and cardiac output were measured pre- and post-exercise in a thermoneutral environment. The fall in mean arterial pressure following exercise was not different between conditions (P= 0.453). Higher post-exercise cardiac output (Δ 0.41 ± 0.17 l min−1; P= 0.027), systemic vascular conductance (Δ 6.0 ± 2.2 ml min−1 mmHg−1; P= 0.001) and stroke volume (Δ 9.1 ± 2.1 ml beat−1; P < 0.001) were seen in Fluid compared to Control, but there was no difference between Fluid and Warm (all P > 0.05). These data suggest that fluid replacement mitigates the post-exercise decrease in cardiac output in endurance-exercise trained men. Surprisingly, exercise in a warm environment also mitigates the post-exercise fall in cardiac output.

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