Abstract
In order to study the long-term effects of prolonged physical training in hypobaric
hypoxia on plasma stress hormone concentrations, male rats (N = 84) were exposed to
progressive running training on a motordriven treadmill for 10, 21 or 56 days, twice
a day and 5 days a week either in hypobaric hypoxic (O2-pressure 740-770 mbar) or in normobaric conditions. The plasma samples were taken
14- 16 hours after the last exercise bout. Plasma corticosterone concentration was
higher in animals trained 10 days in hypobaric conditions than in those trained in
normobaric conditions (1127 ± 158 nmol/l and 710 ± 87 nmol/l, p<0.05, respectively)
while no effect of hypobaric conditions were seen in resting animals. Rats trained
for 21 and 56 days in both normo- and hypobaria had significantly higher plasma corticosterone
levels than the untrained animals. The changes in plasma ACTH and (β-endorphin concentrations
were not significant in any group. According to our corticosterone results, we suggest
that hypobaric hypoxia increases stress of training animals at the beginning of long-erm
training. The absolute work load was the same in both conditions, which probably at
the beginning of training causes more stress to hypobaria trained rats than those
trained in normobaria. Later when the adaptation to hypobaric hypoxia occurs, physical
training itself seems to be responsible for increased plasma corticosterone levels
in hypobaria as well as in normobaria.
Key words
Physical training - hypobaric hypoxia - corticosterone - ACTH - β-endorphin - catecholamines
- rat
