Ftaiti, Foued, Jemni, Monèm, Kacem, Asma, Tabka, Zouhair, Zbidi, Abdelkarim and Grelot, Laurent (2007) Effect of hyperthermia and dehydration on circulating growth hormone concentration. In: 12th annual congress of the European College of Sport Science : book of abstracts. Book of Abstracts of the 12th Annual Congress of the European College of Sport Science in Jyväskylä, Finland 11-14 July 2007, Jyvaskyla, Finland. ISBN 9789517902427

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Abstract

Objective – The aim of this study was to differentiate the effects of dehydration and increased body temperature on growth hormone (GH) secretion during exercise or during passive sitting in either heat or in thermo-neutral conditions.

Methods – Nine healthy volunteer adults (males, 24 61617; 2 yrs, 68 61617; 3 kg, 177 61617; 3 cm, 16 61617; 2 % body fat) performed two 40 min exercise trials and two 50 min passive exposure trials. The exercise trial was 40 min submaximal run on 400 m Astroturf athletic track. It was performed under two conditions: either in thermoneutral conditions (N-Ex, air temperature 18 degree C, air humidity 40%) or in hot environmental conditions (H-Ex, air temperature 33 �degree ��C, air humidity 33%). The passive exposure trials were also performed under two conditions: either in comfortable (N-S, air temperature 18 degrees C, air humidity 40%) or in hot climatic chamber (H-S, air temperature 40 degrees C, air humidity 100%). Plasma growth hormone (GH), plasma volume (PV), tympanic temperature (Tty) and body mass loss (BML) were measured pre and post each trial. Results – The decrease in plasma volume was significantly higher during H-Ex (-9.6 61617; 3%) and H-S (-10.4 61617; 4%) sessions compared to N-Ex and N-S sessions [(-4.5 61617; 2%, p<0.05) and (-0.4 61617; 0.42%, p<0.001)] respectively. The rise in Tty was significantly higher during H-S session (2.9 61617; 0.4 degrees C) (p<0.001) when compared to the other sessions. Plasma GH concentration increased significantly in all trials; only one significant level was reached, that of the H-Ex session (45 61617; 7 ng.ml- 1) (p<0.01). Plasma GH rise was significantly correlated to the increase in Tty, to the increase of BML and the decrease of PV (p<0.01). Conclusions – Our results suggest that core temperature increase has a greater effect on the GH release than water loss and/or plasma volume decrease.

Discussion- Although the rise of temperature in the present study was higher in H-S (+2.5 degrees C) as compared to the N-Ex session (+0.8 degrees C), the increases in GH were statistically the same. Similarly, the rise in GH was higher after H-Ex than after H-S whereas the core temperature was lower (+2.1 vs. 2.9 degrees C). This suggests that core temperature increase (might be associated with other factors) has a greater effect on the GH release than water loss and/or plasma volume decrease. In this line, Stosky et al. (1989) suggested that metabolic factors play a role in the exercise induced GH release even in the absence of hypoglycemia. Furthermore, a positive correlation between maximal difference in glucose level and maximal difference in GH secretory
rate was found during 3-h submaximal cycling exercise (Scheen et al., 1998).

Item Type:	Conference Proceedings
Title of Proceedings:	12th annual congress of the European College of Sport Science : book of abstracts
Additional Information:	[1] Proceedings of the annual congress - European College of Sport Science. [2] On paper author appears as "Jemni Monem"
Uncontrolled Keywords:	Growth hormone, thermoregulation, endurance, dehydration, body temperature
Faculty / School / Research Centre / Research Group:	Faculty of Education, Health & Human Sciences > School of Human Sciences (HUM)
Related URLs:	Publisher Organisation
Last Modified:	09 Oct 2021 04:46
URI:	http://gala.gre.ac.uk/id/eprint/4393

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