Effect of hydration on exercise-induced growth hormone response.
METHODS
Growth hormone (GH) has demonstrated water-retaining effects in subjects at rest, whereas other research has indicated that GH may stimulate sweating. Thus, the aim of this study was to investigate the effect of fluid intake on the exercise-induced GH response.


METHODS
Seven healthy male volunteers (age: 27.4+/-1.3 years, weight: 74.5+/-1.1 kg, height: 179.3+/-2.3 cm) performed a 40-min submaximal rectangular cycling exercise in two different sessions. The first session (Session 1) was performed without water intake, and the second (Session 2) involved the ingestion of spring water (four intakes) corresponding to the volume of water lost during the first session.


RESULTS
In session 1, the water loss was 568+/-32 ml. In Session 2, the volume of water loss was not significantly different from the volume of fluid intake (524+/-16 versus 568+/-32 ml respectively). The decrease in plasma volume was significantly reduced in Session 2 (-6.69+/-1.59% versus -11.3+/-1.89%; P<0.05). In Session 1, the GH concentration was significantly lower than that during Session 2 after 25 min (3.04+/-1.05 versus 5.26+/-1.81; P<0.05) and after 40 min (13.7+/-3.55 versus 17.60+/-4.14 ng/ml; P<0.05) of exercise. The total GH response was significantly lower in Session 1 than in Session 2 (136.6+/-39.2 versus 202.4+/-58.9 ng/ml x min; P<0.05).


CONCLUSIONS
We conclude that the exercise-induced GH response decreases when exercise is performed without fluid intake.
Peyreigne
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Département de Physiologie, Laboratoire de Physiologie des Interactions, UPRES EA 701, Institut de Biologie, Faculté de Médecine, Boulevard Henri IV 34060 Montpellier, France. secphysio@medecine.univ-montp1.fr
Bouix
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Fédou
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Mercier
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D000328:Adult; D001642:Bicycling; D001834:Body Water / Q000378:metabolism*; D004326:Drinking; D015444:Exercise / Q000502:physiology*; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D010953:Plasma Volume; D013997:Time Factors; D014870:Water Loss, Insensible
D019382:Human Growth Hormone