Effects of acute or chronic heat exposure, exercise and dehydration on plasma cortisol, IL-6 and CRP levels in trained males

摘要

This study examined the acute and chronic effects of euhydrated and hypohydrated heat exposure, on biomarkers of stress and inflammation. Eight trained males [mean (SD) age: 21 (3) y; mass: 77.30 (4.88)?kg; V?O2max: 56.9 (7.2)?mL?kg?1?min?1] undertook two heat acclimation programmes (balanced cross-over design), once drinking to maintain euhydration and once with restricted fluid-intake (permissive dehydration). Days 1, 6, and 11 were 60?min euhydrated exercise-heat stress tests (40?°C; 50% RH, 35% peak power output), days 2–5 and 7–10 were 90?min, isothermal-strain (target rectal temperature: 38.5?°C) exercise-heat sessions. Plasma was obtained pre- and post- exercise on day 1, 2, and 11 and analysed for cortisol, interleukin-6 (IL-6), and C-reactive protein (CRP). Cortisol and CRP were also assessed on day 6. IL-6 was elevated following the initial (acute) 90?min isothermal heat strain exercise-heat exposure (day 2) with permissive dehydration ((pre exercise: 1.0?pg?mL?1[0.9], post-exercise: 1.8?pg?mL?1[1.0], P?=?.032) and when euhydrated (pre-exercise: 1.0?pg?mL?1[1.4], post-exercise: 1.6?pg?mL?1[2.1], P?=?.048). Plasma cortisol levels were also elevated but only during permissive dehydration (P?=?.032). Body mass loss was strongly correlated with Δcortisol (r?=??0.688, P?=?.003). Although there was a trend for post-exercise cortisol to be decreased following both heat acclimation programmes (chronic effects), there were no within or between intervention differences in IL-6 or CRP. In conclusion, acute exercise in the heat increased IL-6 and cortisol only when fluid-intake is restricted. There were no chronic effects of either intervention on biomarkers of inflammation as evidenced by IL-6 and CRP returning to basal level at the end of heat acclimation.