K. Engfred et al., HYPOXIA AND TRAINING-INDUCED ADAPTATION OF HORMONAL RESPONSES TO EXERCISE IN HUMANS, European journal of applied physiology and occupational physiology, 68(4), 1994, pp. 303-309
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.