Exercise Performance Of Middle-age And Young With Similar Vo2max Is Not Different Under Heat Stress

Abstract

The aging process may impair exercise tolerance under heat stress conditions. However, it is not clear if this impairment is due to reduction on aerobic capacity and/or thermoregulatory function. PURPOSE: to compare the exercise tolerance under heat stress between middle-age (MA) and young runners (YO) with similar aerobic capacity using self pace or fixed workload intensity. METHODS: 7 middle-age and 7 young male (age 54 ± 2 and 28 ± 1 years old; VO2max 58 ± 4 and 61 ± 5 ml·kg-1·min-1, body fat 12 ± 1 and 10 ± 2%, respectively, mean ± SD) runners with similar aerobic capacity underwent to two trials on counterbalanced order: 10 km of self-pace run (RSelf) and fixed work load (RFixed, 90% of the best race speed) until fatigue on a treadmill in a hot environment (40 °C and 30% RH). Total time to exhaustion (TT), average speed (AS), final rectal temperature (Tre), heat storage rate (HS), total sweat rate (SR), sweat sensitivity (SR/ΔTre), number of activated sweat glands (ASG) and sweat rate per sweat gland (SR/SG) were measured or calculated. ANOVA two-way with repeated measures and Bonferroni's post hoc test were used to compare the results. RESULTS: We observed no differences between YO and MA for TT, AS, final Tre, HS and SR (p>0.05) on RSelf and RFixed. SR/SG and SR/ΔTre were smaller for MA than YO on RSelf or RFixed and ASG were higher for MA than YO on RSelf or RFixed (p <0.05).TableCONCLUSION: We concluded that exercise tolerance in a hot environment of young and middle age runners with same aerobic capacity is similar probably by the higher number of recruited sweat glands, despite of smaller SR/SG on MA. Supported by CAPES/SETEC, CNPq and FAPEMIG.