Original articles  ENDOCRINOLOGY 

The Journal of Sports Medicine and Physical Fitness 2003 December;43(4):554-8

Copyright © 2009 EDIZIONI MINERVA MEDICA

lingua: Inglese

Acute exposure to moderate high altitude decreases growth hormone response to physical exercise in untrained subjects

Gutiérrez A., González-Gross M., Ruiz J. R., Mesa J. L. M., Castillo M. J.

Department of Physiology, School of Medicine and School of Sport Sciences, University of Granada, Granada, Spain

Aim. Phys­ical exer­cise in rec­re­a­tional moun­tain ­sports is fre­quently per­formed ­without accli­mat­iza­tion to ­hypoxic con­di­tions. ­Hypoxia may ­modify the hor­monal and meta­bolic adap­tive ­response to exer­cise ­depending on the ­type of exer­cise and on the phys­ical fit­ness of the sub­ject. ­This ­study ­aims at inves­ti­gating the ­growth hor­mone (GH) ­response to sub­max­imal exer­cise ­after ­acute expo­sure to mod­erate ­high alti­tude.
­Methods. Ten ­trained (T) and 10 ­untrained (UT) ­male vol­un­teers (­mean age 23.8±3.2 ­y) under­went, in ­random ­order, 2 sub­max­imal exer­cise (ergoc­ycle) ­tests of the ­same abso­lute inten­sity. One ­test was per­formed at ­their ­habitual ­living alti­tude (690 m ­above sea ­level); the ­other, ­after ­acute expo­sure to 2325 m ­above sea ­level. ­Plasma ­levels of GH, ­Insulin-­like ­growth ­factor-1 (IGF-1) and lac­tate ­were meas­ured ­before and imme­di­ately ­after the exer­cise ­tests.
­Results. ­Plasma GH ­levels ­increased ­after exer­cise (p<0.05) in ­both experi­mental con­di­tions, and for ­both T and UT sub­jects. ­Hypoxia ­decreased the GH-IGF-1 ­response to exer­cise in the UT ­group. By con­trast, the GH-IGF-1 ­response to exer­cise was not mod­i­fied in the T ­group. The ­increase in ­plasma lac­tate ­levels ­induced by exer­cise was ­much ­higher in the UT ­than in the T ­group, and it was not ­affected by ­hypoxia.
Con­clu­sion. ­Acute expo­sure to ­hypoxia ­blunts the GH ­response to sub­max­imal phys­ical exer­cise in ­untrained indi­vid­uals.