Distance running: speed matters for endurance

When it comes to improving endurance performance, what are the aspects of fitness that really count, and which athletes should focus on? Regular readers will no doubt be aware that maximal oxygen uptake (VO2max – the maximum capacity that an athlete can absorb, transport and deliver to working muscles for energy release) has long been considered absolutely pivotal⁽¹⁾. This is unsurprising since sustained endurance performance efforts of over ten minutes or so relies very heavily on the aerobic system, where muscular energy is derived directly from burning carbohydrate and fat using oxygen.

Other key factors in endurance performance

Another key component of fitness that is known to be important is ‘muscle economy’. High levels of muscle economy during activities such as running, cycling, swimming etc means that less oxygen is required to sustain a sub-maximal pace, which leads to less energy expenditure and less fatigue – in turn leaving more in the tank for the higher-effort sections of a race. Early research on cross-country runners discovered that just two factors – VO2max and running economy - could account for 92% of the variance in performance during an 8000m race⁽²⁾. Also, running economy, like VO2max, has been used to estimate marathon pace in elite runners⁽³⁾. In another study, researchers were mystified as to why the performances of elite Eritrean runners were consistently better than those of Spanish elites despite a similar VO2 max⁽⁴⁾. Testing on both groups revealed that the key physiological difference was the exceptional running economy of the African runners; at 21kmh (13.0mph), the Eritreans needed to consume just 65.9mls of oxygen per kilo per kilometre - compared with 74.8mls of oxygen for the Spanish runners (see figure 1)!

Figure 1: Oxygen consumption per kilo per kilometre at 21kmh