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Erschienen in:
01.03.2016 | Original Article
RhEPO improves time to exhaustion by non-hematopoietic factors in humans
Erschienen in: European Journal of Applied Physiology | Ausgabe 3/2016
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Purpose
Erythropoietin (EPO) controls red cell volume (RCV) and plasma volume (PV). Therefore, injecting recombinant human EPO (rhEPO) increases RCV and most likely reduces PV. RhEPO-induced endurance improvements are explained by an increase in blood oxygen (O2) transport capacity, which increases maximum O2 uptake (\(\dot{V}\)O2max). However, it is debatable whether increased RCV or \(\dot{V}\)O2max are the main reasons for the prolongation of the time to exhaustion (t
lim) at submaximal intensity. We hypothesized that high rhEPO doses in particular contracts PV such that the improvement in t
lim is not as strong as at lower doses while \(\dot{V}\)O2max increases in a dose-dependent manner.
Methods
We investigated the effects of different doses of rhEPO given during 4 weeks [placebo (P), low (L), medium (M), and high (H) dosage] on RCV, PV, \(\dot{V}\)O2max and t
lim in 40 subjects.
Results
While RCV increased in a dose-dependent manner, PV decreased independent of the rhEPO dose. The improvements in t
lim (P +21.4 ± 23.8 %; L +16.7 ± 29.8 %; M +44.8 ± 62.7 %; H +69.7 ± 73.4 %) depended on the applied doses (R
2 = 0.89) and clearly exceeded the dose-independent \(\dot{V}\)O2max increases (P −1.7 ± 3.2 %; L +2.6 ± 6.8 %; M +5.7 ± 5.1 %; H +5.6 ± 4.3 %) after 4 weeks of rhEPO administration. Furthermore, the absolute t
lim was not related (R
2 ≈ 0) to RCV or to \(\dot{V}\)O2max.
Conclusions
We conclude that a contraction in PV does not negatively affect t
lim and that rhEPO improves t
lim by additional, non-hematopoietic factors.