• o ₂ max
• blood doping
• erythropoietin
• haemoglobin

By the 1930s it was clear that champion endurance athletes had remarkably high maximal O₂ uptake (o₂max).¹ In the 1950s, 1960s, and 1970s, classic studies were performed on the physiological determinants of o₂max and on its key role in endurance performance.^2–4 During this time there was much debate on O₂ delivery versus O₂ extraction as the “limiting factor” for o₂max.^5,6 Observations during this era clearly established the role of maximal cardiac output as a determinant of o₂max, and very high maximal cardiac output values were seen in champion endurance athletes.² In addition, the important role of blood volume and total body haemoglobin as determinants of o₂max also emerged (fig 1).^2,7–9 In an effort to better understand the physiological determinants of o₂max, studies were then conducted that attempted to manipulate O₂ delivery using a variety of approaches including altered concentrations of inspired O₂, drugs that speed or slow the heart, and, as will be discussed here, techniques that altered total body haemoglobin and haemoglobin concentration.^10,11

In general, by the 1970s it was clear that manoeuvres that increased total body haemoglobin increased o₂max and manoeuvres that reduced total body haemoglobin reduced o₂max. …