Effect of hyperthermia and physical activity on circulating growth hormone

Foued Ftaiti, Monèm Jemni, Asma Kacem, Zaouali Monia, Zouhair Tabka, Abdelkarim Zbidi, Laurent Grelot

Research output: Contribution to journalJournal Articlepeer-review

7 Citations (Scopus)

Abstract

The aim of this study was to differentiate the effects of hyperthermia and physical activity on circulating growth hormone (GH) secretion. Nine healthy volunteer adults performed two 40 min exercise trials and two 50 min passive standing trials. The exercise was performed in either thermo-neutral (N-Ex: air temperature 18 degrees C, air humidity 40%, and wet bulb globe temperature (WBGT) 17.7 degrees C) or hot environmental conditions (H-Ex: air temperature 33 degrees C, air humidity 30%, and WBGT 34.6 degrees C). The passive exposure trials were also performed in either a comfortable (N-P: air temperature 18 degrees C, air humidity 40%, and WBGT 17.7 degrees C) or a hot climatic chamber (H-P: air temperature 40 degrees C, air humidity 100%, and WBGT 97.1 degrees C). Plasma GH, plasma volume (PV), tympanic temperature (Tty), and body mass loss (BML) were measured before and after each trial. The decrease in PV was significantly higher during H-Ex and H-P sessions than during N-Ex and N-P sessions. Comparisons showed significantly lower BML in the N-Ex session (1.5% +/- 0.3%) than in the H-Ex and H-P sessions (2.1% +/- 0.3% and 1.9% +/- 0.2%, respectively) (p < 0.001). The rise in Tty was significantly higher during the H-P session (2.9 +/- 0.4 degrees C) (p < 0.001) when compared with the other sessions. Plasma GH concentration increased significantly during all the trials, particularly during the H-Ex session (45 +/- 7 ng.mL-1) (p < 0.01). Both exercise and heat exposure, separately, are sufficient to increase significantly the plasma GH concentration, and their combined effect induced a highly synergistic rise in GH.
Original languageEnglish
Pages (from-to)880-887
Number of pages8
JournalApplied physiology, nutrition, and metabolism = Physiologie appliquée, nutrition et métabolisme
Volume33
DOIs
Publication statusPublished - 2008
Externally publishedYes

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