Endurance running performance depends on a complex interplay of factors, including: (1) a high maximal oxygen uptake (VO₂max); (2) the ability to sustain a high percentage of VO₂max for long periods of time (fractional utilisation of VO₂max); and (3) the ability to move efficiently (ie, "cost of running" or "running economy").1 2 Although VO₂max and fractional utilisation of VO₂max have been extensively studied as determinants of running performance, by comparison, running economy has been relatively ignored in the scientific literature, though it may be the critical factor determining endurance running performance.1 Differences amongst elite athletes in a variety of endurance sporting events other than running (particularly road cycling) have also been shown to be highly related to differences in economy (or efficiency).3 The physiological index of endurance performance that improved most in seven-time winner of the Tour de France Lance Armstrong as he matured from age 21 to 28 years was gross mechanical efficiency (+8%), whereas his VO₂max remained relatively unchanged.4

Black athletes of East African origin (Kenyans and Ethiopians) dominate most endurance running events, from the 5000 m track event to the marathon. Many of the best performances in these events have been achieved by Kenyans (49%) and Ethiopians (15%). In recent years, other African endurance runners (from South Africa, Tanzania, Zimbabwe and, more recently, Eritrea) have also attained excellent results in international competition. A lower cost of running, that is, better economy, has been demonstrated in some top-level East African runners5 6 and in runners from other parts of Africa compared to their Caucasian counterparts.7 This phenomenon could account, at least in part, for their superior competition performance.

The Cross-Country World Championship provides an …