Purpose This study evaluated whether recombinant human erythropoietin (rhEpo) treatment combined with hypoxia provided an additive effect on hemoglobin mass (Hbmass) and peak oxygen uptake (VO2peak) compared with altitude or rhEpo alone. Methods Thirty-nine participants underwent two interventions, each containing 4-wk baseline (PRE 1-4), 4-wk exposure at sea level or 2320 m of altitude (INT 1-4), and 4-wk follow-up (POST 1-4). Participants were randomly assigned to 20 IU·kg-1 rhEpo or placebo injections every second day for 3 wk during the exposure period at sea level (SL-EPO, n = 25; SL-PLA, n = 9) or at altitude (ALT-EPO, n = 12; ALT-PLA, n = 27). Results Hbmass displayed a significant time-treatment effect (P < 0.001) when comparing ALT-EPO and ALT-PLA. Specifically, the increase in Hbmass was higher (P < 0.05 to P < 0.001) for ALT-EPO from INT 2 to POST 3 except for POST 2. Similarly, a significant time-treatment effect (P < 0.001) existed for changes in Hbmass when comparing ALT-EPO with SL-EPO, with the increase in Hbmass being higher (P < 0.01 to P < 0.001) for ALT-EPO from INT 2 to POST 4. A significant time-treatment effect was present when SL-PLA was compared with ALT-PLA (P < 0.05) and SL-EPO (P < 0.05). For VO2peak, the time-treatment interaction was not significant when comparing ALT-EPO to ALT-PLA. However, when ALT-EPO was compared with SL-EPO, a significant time-treatment interaction existed (P < 0.001) due to a decrease in VO2peak during altitude. Conclusions The combined treatment of microdoses of rhEpo and altitude exposure results in an additive increase in Hbmass but does not significantly enhance VO2peak compared with each treatment alone.
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