Endocrine responses during exercise-heat stress: effects of prior isotonic and hypotonic intravenous rehydration

European Journal of Applied Physiology and Occupational Physiology
J W CastellaniV D Castracane

Abstract

Exercise following exercise-induced dehydration (EID) has been shown to elevate concentrations of plasma norepinephrine (NE) and hypothalamic-pituitary-adrenal axis hormones. However, it is not known how intravenous (i.v.) rehydration (Rh) with isotonic (ISO) or hypotonic (HYPO) saline affects these hormone concentrations. It was hypothesized that HYPO, versus ISO, would lead to lower plasma NE and cortisol concentrations ([CORT]) during subsequent exercise following EID due to a decrease in plasma sodium concentration [Na+]. Eight non-heat acclimated men completed three experimental treatments (counterbalanced design) immediately following EID (33 degrees C) to -4% body mass loss. The Rh treatments were i.v. 0.9% NaCl (ISO, 25 ml x kg[-1]), i.v. 0.45% NaCl (HYPO, 25 ml x kg[-1]), and no fluid (NF). After Rh and rest (2 h total), the subjects walked at 53-54 percent of maximal O2 uptake for 45 min at 36 degrees C. After Rh, the following observations were made before/during exercise: percentage change in plasma volume (PV) was lower in NF compared to ISO and HYPO but similar between ISO and HYPO; delta[Na+] was similar between ISO and NF and higher in ISO compared to HYPO; delta plasma NE was higher in NF compared to ISO and HY...Continue Reading

Citations

Jan 17, 2002·Neurotoxicology and Teratology·S E Chia, K J Teo
Apr 27, 2011·Clinical Journal of Sport Medicine : Official Journal of the Canadian Academy of Sport Medicine·Elliot J Pellman
Jun 6, 2006·Nutrition Journal·Wataru AoiToshikazu Yoshikawa
Oct 23, 2013·Journal of Athletic Training·Brendon P McDermottCarl Maresh
Apr 7, 2010·Sports Medicine·Simon Piet van RosendalJeff Scott Coombes
Jul 23, 2016·Advances in Physiology Education·Roger A L Dampney
Oct 7, 2017·Journal of Athletic Training·Brendon P McDermottWilliam O Roberts

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