Hypoxia and training-induced adaptation of hormonal responses to exercise in humans.
To establish whether or not hypoxia influences the training-induced adaptation of hormonal responses to exercise, 21 healthy, untrained subjects (2) years, mean (SE)] 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 (VO2max), 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 sampled before, during and at the end of exhaustive cycling at sea level (85% of pretraining VO2max). VO2max increased by 12 (2)% with no significant difference between groups, whereas endurance improved most in group 1 (P < 0.05). Training-induced changes in response to exercise of noradrenaline, adrenaline, growth hormone, beta-endorphin, glucagon, and insulin were similar in the three groups. Concentrations of erythropoietin and 2,3-diphosphoglycerate at rest did not change over the training period. In conclusion, within 5 weeks of training, no further adaptation of hormonal exercise responses takes place if intensity is increased above 70% VO2max. Furthermore, hypoxia per se does not add to the training-induced hormonal responses to exercise.
Engfred
K
K
Department of Anaesthesia, Rigshospitalet, Copenhagen, Denmark.
Kjaer
M
M
Secher
N H
NH
Friedman
D B
DB
Hanel
B
B
Nielsen
O J
OJ
Bach
F W
FW
Galbo
H
H
Levine
B D
BD
D000222:Adaptation, Physiological; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002395:Catecholamines / Q000097:blood; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000097:blood; D006728:Hormones / Q000097:blood*; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology*; D007328:Insulin / Q000097:blood; D008297:Male; D010806:Physical Education and Training; D005082:Physical Exertion
D001786:Blood Glucose; D002395:Catecholamines; D005230:Fatty Acids, Nonesterified; D006728:Hormones; D007328:Insulin; D000324:Adrenocorticotropic Hormone; D013006:Growth Hormone