Effects of acute or chronic heat exposure, exercise and dehydration on plasma cortisol, IL-6 and CRP levels in trained males. (October 2018)

• Record Type: Journal Article
• Authors: Costello, Joseph T.; Rendell, Rebecca A.; Furber, Matthew; Massey, Heather C.; Tipton, Michael J.; Young, John S.; Corbett, Jo
• Is Part Of: Cytokine. Volume 110(2018)
• Page Start: 277
• Page End: 283
• Publication Date: 2018-10
• Subjects: Thermoregulation -- Stress -- Extreme environments -- Acclimatization -- Acclimation; Cytokines -- Periodicals; 571.844
• DOI: 10.1016/j.cyto.2018.01.018
• Languages: English
• ISSNs: 1043-4666

Abstract

Highlights: Acute exercise in the heat increases IL-6 regardless of hydration status. Acute exercise in the heat increases cortisol only when fluid-intake is restricted. This cortisol response was strongly correlated with whole body sweat loss. Cortisol, IL-6 and CRP were not augmented after heat acclimation. Abstract: 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; V̇O2max : 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.