Erythropoietin (EPO) is a hormone produced by the kidneys when a low oxygen pressure is detected in the blood. EPO release in the blood circulation triggers new red blood cells production and this results in hemoglobin (Hb) levels elevation. An elevation in Hb concentration in the blood will increase oxygen carrying capacity. Studies in athletes have shown that increased Hb concentration is associated with improved endurance.
The search for new methods to increase EPO concentration, that do not violate the rules of WADA, has been of interest to scientists. Five years ago, a research group from Belgium showed that breathing 100% normobaric oxygen for 2 h resulted in 60% increase in EPO after 36 h (Ballestra et al., 2006). Although no data in performance were published in this study, we can assume that this elevation in EPO would have produced a substantial improvement in performance. Few days ago, another group of researcher from Slovenia and Sweden reported totally different results in aerobically fit males (Keramidas et al., 2011). The results suggested that a short period of normobaric oxygen breathing does not increase EPO concentration.
Whatever the reasons for this debate, the area remains of high interest with, potentially, practical applications in the future.