Increased air velocity during exercise in the heat leads to equal reductions in hydration shifts and interleukin-6 with age.

Abstract

The effectiveness of increased air velocity in reducing hydration shifts and physiological strain during work in the heat was examined in young and older males. Ten young (mean ± SE, 24 ± 1 years) and 10 older (59 ± 1 years) males, matched for height, mass, and body surface area, cycled 4 × 15-min at moderate-to-heavy heat production (400 W), with 15-min rest separations between exercise bouts (final recovery 30 min), while wearing work clothing in humid heat (35 °C, 60 % relative humidity) under low (~0.5 m s(-1)) and high (~3.0 m s(-1)) air velocity. Rectal temperature (T re) and heart rate were measured continuously, whereas hydration indices and interleukin (IL)-6 were measured at rest (PRE) and following the final recovery (POST). Young and older males experienced similar thermal and cardiovascular strain within the low (T re end-exercise: young = 38.28 ± 0.11, older = 38.31 ± 0.08 °C) and high (T re end-exercise: young = 37.94 ± 0.08, older = 37.87 ± 0.08 °C) air velocity conditions, with a reduced increase in both groups in high compared to low. Percent changes in plasma volume were similarly greater during the low (young = -10.9 ± 1.2, older = -10.8 ± 0.9 %) compared to high (young = -5.7 ± 0.6, older = -6.9 ± 0.7 %) condition for both groups. Despite elevated IL-6 at PRE in the older males, the IL-6 absolute change was similar between young (low = +4.10 ± 0.95, high = +0.99 ± 0.32 pg mL(-1)) and older (low = +3.58 ± 0.83, high = +1.24 ± 0.28 pg mL(-1)) males yet greater during the low compared to high condition. Increased air velocity was effective in reducing the increase in hydration shifts and physiological strain (i.e. IL-6, thermal and cardiovascular strain) equally in young and older males.