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The determinants of endurance performance

Sport scientists are constantly trying to understand how physiological variables measured in the laboratory can help explain endurance performance. It is important not only in helping to identify performance potential, but also for prescribing training loads and monitoring training adaptations. Broadly, the ‘big three’ have been identified as

  • The maximal oxygen uptake (VO2max)
  • The ability to utilize a high fraction of VO2max for a very long time – aerobic endurance
  • The economy of movement during exercise (E)

Here, we aim to introduce these three parameters. Two others can help understanding performances of athletes of similar VO2max, aerobic endurance, and economy levels. Another factsheet on (a) the speed at which the oxygen uptake responds at exercise onset, and (b) the anaerobic capacity or ability to produce energy via non oxidative pathways, is available in our PBscience library.

The upper ceiling – the maximal oxygen uptake

Endurance_determinants_graphsThe VO2max reflects an individual’s maximal rate of aerobic energy expenditure1 and is traditionally determined from the performance of an incremental test to exhaustion (see figure right), although other tests have been proposed to estimate this variable in the field. The associated power output or running speed can be estimated providing the exercise economy of the athlete is known (= VO2max x E).

Fractional utilization and the ’lactate threshold’

The ability to maintain a high fraction of VO2max for a long period of time, i.e. a high aerobic endurance is required to perform well in long events2.

More specifically, this can be pinpointed by the exercise intensity corresponding to an increase in blood lactate above resting levels, the ‘lactate threshold’ (LT). This intensity is important since it indicates the powerfulness of the oxidative capacities of the body (i.e. utilisation of oxygen) and it represents the boundary between the moderate and heavy intensity domains (see our factsheet on this).

A little higher up on the exercise intensity scale we meet the upper boundary of the heavy exercise intensity domain: the maximal lactate steady state3. The MLSS is another ‘threshold’ phenomenon but differs to the first LT as it represents the highest exercise intensity at which blood lactate (though elevated) does not accumulate over time. The MLSS is particularly well related (and not very far off) to one hour performances in cycling exercise4.

It’s not the size of your car engine, but its fuel economy!

Exercise economy has been defined as the VO2 required at a given absolute exercise intensity5 (it is represented as an angle on the VO2-intensity relationship displayed on the Figure above: The lower the VO2, more economical you are at a given intensity).

There is considerable inter-individual variability in the oxygen cost of sub-maximal exercise, even in individuals of similar aerobic fitness or similar performance capability, probably in part due to inter-individual muscle fibre distribution.

What is the most important to develop?

When you first start endurance training, all three will improve, but the greatest changes will occur in your lactate threshold and VO2max: hence why performance improves dramatically over the first season. However, it gets harder and harder to build upon these improvements year by year. It is then exercise economy, the speed of your oxygen uptake response and your anaerobic capabilities, which add to performance gains. For instance, you may have come across the adage that it takes “10 years to build a champion”? It is quite possibly true! Economy seems to be highly related to years in a sport, and the total training volume an athlete has completed6.

Take home message

Broadly speaking, training in endurance sport will increase LT and VO2max early on, with these gains reducing the more time you have in the sport. Economy improvement appears to be a ‘side effect’ of accumulating years in a sport – specifics can be done, but less research is available to prove conclusively the worth of such approaches. It is perhaps fair to say that since top class performers have comparatively similar aerobic fitness (LT and VO2max), it might only be improved economy that allows performance differentiation.

Endurance_determinants_schematic

REFERENCES

1.   Bassett, D. R. Jr & Howley, E. T. Med Sci Sports Exerc 2000, 32, 70-84.

2.   Coyle, E. F. et al. J Appl Physiol 1988, 64, 2622-2630.

3.   Beneke, R. Med Sci Sports Exerc 1995, 27, 863-867.

4.   Coyle, E. F. et al. Med Sci Sports Exerc 1991, 23, 93-107.

5.   Coyle, E. F. et al. Med Sci Sports Exerc 1992, 24, 782-788.

6.   Lucia, A. et al. Med Sci Sports Exerc 2002, 34, 2079-2084.