Effects of Maximal and Submaximal Exercise under Normoxic and Hypoxic Conditions on Serum Erythropoietin Level

Abstract

This study was carried out to investigate the influence of different exercise regimens on serum immunoreactive erythropoietin concentration (EPO). The same untrained male subjects performed bouts of maximal and submaximal exercise (60 min at 60% of maximal performance) under normoxia (n = 10) and normobaric hypoxia (PIO₂ 92 mmHg, n = 9). Five of them were exposed to hypoxia for 90 min under resting conditions (RTH). [EPO] was unchanged up to five hours after maximal (MEN) and submaximal (SEN) exercise under normoxia. After RTH, [EPO] increased after 3 hours by 5.0 mU/ml (p < 0.01). Submaximal exercise under hypoxia (SEH) led to a similar increase in [EPO] (after 3 hours: + 5.5 mU/ml), which remained elevated the following days (after 24 h: + 6.1 mU/ml, 48 h: + 5.3 mU/ml; ANOVA p < 0.001). Maximal exercise under hypoxia (MEH) had no significant effect. The results indicate that exercise has no immediate effect on serum [EPO], whereas the higher EPO level one and two days after SEH could result from the occurring hemodilution as is indicated by a slight negative correlation between [EPO] and Hct (r = 0.59, p < 0.001). The number of reticulocytes increased after all hypoxic experiments and after MEN without any correlation to [EPO].

Key words

Immunoreactive erythropoietin - hypoxia - renal blood flow - plasma volume - reticulocytes