Amateur runners: hop or hope for better performance?

Which aspects of fitness really matter for recreational endurance athletes? Once upon a time, the key yardstick of endurance performance was maximum aerobic capacity – more technically known as ‘VO2max’ (measured in millilitres of oxygen per kilo of bodyweight per minute – ml/kg/min). This describes the maximum capacity of the body to absorb, transport and deliver oxygen to exercising muscles – crucial because unlike carbohydrate and fat (the other components of fuelling), oxygen cannot be stored in the body. In short this means the faster oxygen can be absorbed and delivered to working muscles, the higher the intensity of exercise that can be sustained.

Not just oxygen amounts

As our understanding of sports physiology has progressed however, we now know that while important, VO2max is not necessarily the be all and end all for endurance performance. Evidence has accumulated that a much better measure of an individual’s aptitude for success in endurance events is something called ‘maximal lactate steady state’ –or MLSS for short^(1,2). This measure is defined as the maximum workload that the body can sustain without the rapid accumulation of lactate in the bloodstream (which would otherwise force the person to slow down or stop)⁽³⁾. In short, an athlete with a high MLSS value is better able to sustain a high workload for long periods of time than another athlete with a higher VO2max but lower MLSS.

Efficiency matters too

While MLSS is a good measure of endurance performance, it’s not enough because there’s another key factor at play – efficiency. Muscle efficiency (more correctly known as muscle economy) refers to how efficient the muscles are in terms of oxygen usage at producing force during sub-maximal exercise (ie not flat out). The higher the economy of muscles during exercise, the less oxygen is needed to propel the athlete at a given sub-maximal speed.

Because endurance events such as marathons and triathlons are not run flat out all the way, but at a sustainable sub-maximal speed, muscle economy actually plays a very important role in determining overall endurance performance. Moreover, studies unequivocally demonstrate that elite athletes have much higher levels of muscle economy than their amateur or recreational counterparts. In other words – muscle economy and high levels of endurance go hand in hand.

To give you an idea of the importance of muscle economy, one study of collegiate cross-country team members discovered that just two factors – maximum aerobic capacity (VO2max) and running economy - could account for 92% of the variance in performance during an 8000m running race⁽⁴⁾. Also, running economy has been used as a key parameter (along with oxygen uptake figures) to predict marathon pace in elite runners⁽⁵⁾.

Perhaps even more persuasive is another study in which researchers compared elite Eritrean runners with elite Spanish runners⁽⁶⁾. Although both groups had very similar maximum aerobic capacities, the researchers were mystified as to why the performances of the Eritrean runners were consistently better than those of the Spaniards. 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)!

From the above, you might assume that improving running economy is only important for elite runners. However, this is not true. A 2017 study on recreational runners found that running performance was very closely related to running economy⁽⁷⁾. In other words, higher levels of running economy in these amateur runners were very strongly associated with superior running performance. So while excellent muscle economy is a hallmark of elite runners, even recreational and amateur runners can expect better performance with improved economy.

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