Abstract
Increases in core temperature (T (c)) augment stress hormones and neurotransmitters; however, the effect of different T (c) tolerated with varying fitness levels during uncompensable exertional heat stress (EHS) is unclear. The purpose was to examine the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic-adrenomedullary system (SAS) responses during uncompensable EHS in trained (TR) versus untrained (UT) males. Twelve TR and 11 UT (VO(2peak) = 70 +/-2 and 50 +/- 1 mL kg of lean body mass(-1) min(-1)) walked on a treadmill to exhaustion (EXH) in 40 degrees C (dry), dressed in protective clothing. PRE and 0.5 degrees C T (c) increments from 38.0-40.0 degrees C/EXH venous blood was obtained. Cortisol responded to absolute thermal strain, increasing throughout EHS and independent of fitness. Adrenocorticotropic Hormone, Norepinephrine, and Dehydroepiandrosterone-Sulphate responded to relative thermal strain with similar EXH values, despite higher T (c) tolerated for TR (39.7 degrees C) than UT (39.0 degrees C). Epinephrine, Growth Hormone (GH), and Aldosterone increased initially, with a plateau above 38.5 degrees C T (c). Findings demonstrate the complexity of the HPA axis, SAS, and T (c) relationship, with the stress pathways responding largely to relative thermal strain, although some hormones exhibited a clamping response likely as a protective mechanism. For the TR, evidence existed for a reduced pituitary sensitivity to glucocorticoids and the amplified GH may have contributed to their greater T (c) tolerated.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.