HYPOXIA AND TRAINING-INDUCED ADAPTATION OF HORMONAL RESPONSES TO EXERCISE IN HUMANS

To establish whether or not hypoxia influences the training-induced ad aptation of hormonal responses to exercise, 21 healthy, untrained subj ects [26 (2) years, mean (SE)I were studied in three groups before and after 5 weeks' training (cycle ergometer, 45 min.day(-1), 5 days.week (-1)). Group 1 trained at sea level at 70% maximal oxygen uptake (VO2m ax), group 2 in a hypobaric chamber at a simulated altitude of 2500 m at 70% of altitude VO2max, and group 3 at a simulated altitude of 2500 m at the same absolute work rate as group 1. Arterial blood was sampl ed before, during and at the end of exhaustive cycling at sea level (8 5% of pretraining VO2max). VO2max increased by 12 (2)% with no signifi cant difference between groups, whereas endurance improved most in gro up 1 (P<0.05). Training-induced changes in response to exercise of nor adrenaline, adrenaline, growth hormone, beta-endorphin, glucagon, and insulin were similar in the three groups. Concentrations of erythropoi etin and 2,3-diphosphoglycerate at rest did not change over the traini ng period. In conclusion, within 5 weeks of training, no further adapt ation of hormonal exercise responses takes place if intensity is incre ased above 70% VO2max. Furthermore, hypoxia per se does not add to the training-induced hormonal responses to exercise.