Boning, D., Maassen, N., & Pries, A. (2009). Mechanisms of doping with erythropoietin or blood infusion. ACSM 56th Annual Meeting, Seattle, Washington. Presentation number 744.

"It is usually believed that doping with erythropoietin or blood infusion is only effective by increasing the oxygen content of arterial blood because of a rise in hemoglobin concentration."

This speculative study analyzed the simple hypothesis underlying erythropoietin and blood infusion to see if there are any possible additional factors. Publications on the physiological relevance of accompanying hematocrit (hct) increases and on additional effects of erythropoietin were evaluated.

An improvement of aerobic performance by an augmented hemoglobin concentration can only result if the optimal hct is not transgressed; above this value maximal cardiac output is reduced by the steep increase of blood viscosity. Therefore, the enlarged oxygen content of blood might only be useful if the normal hct of man during exercise is suboptimal. Investigations on this topic in man seem not to exist, but one may speculate that lower hct values were selected because of health risks. Other factors for a performance improvement by erythropoietin and partly by blood infusion might be: an augmented diffusion capacity for oxygen in lungs and tissues, an increased percentage of young red cells with good functional properties, an increase of the blood volume, a vasoconstriction, a reduction of damage by radicals, an improvement of mood by cerebral effects of the hormone, and placebo effects. The importance of the latter is unknown since perfect double blind studies are rare. Perfect “natural” blood dopers (horses, dogs, lamas), which increase hct only during exercise to 60 % by pumping a red cell concentrate from the spleen into the systemic circulation, possess very small erythrocytes preventing a large increase in viscosity. At the same time they increase the circulating blood volume by approximately 40% and their maximal oxygen uptake reaches nearly twice the value of human athletes.

Implication. Blood doping in the natural world is multifactorial and not restricted to the increase in arterial oxygen content. Until adequately controlled studies are performed on humans, which of the hypothetical factors can be established as fact for improving physical performance remain in the domain of speculation.

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