lactate testing

Lactate analysis has been used by many athletes and physiologists over the last decade as a tool for predicting endurance performance. Specifically, the higher the percentage of VO2max, or the higher the pace at which the lactate threshold occurs, the fitter the athlete. Many researchers have placed the lactate threshold - the maximum concentration that an athlete can maintain during a steady state effort - at around 4mmol/L. But others have found that lactate concentrations can vary widely, with some athletes capable of maintaining concentrations as high as 8mmol/L over sustained periods.

A new study has measured the lactate response to a cycling time trial in which the participants were instructed to cycle as far as they could in a period of one hour, with lactate samples collected every 10 minutes. The athletes averaged 40.8k during the trial at an average 83% of maximum heart rate. Lactate concentrations ranged between

5 and 12mmol/L, with an overall average of 7.6mmol/L. Mean lactate concentrations and pace remained relatively stable throughout, suggesting the athletes were maintaining a constant maximum steady state effort.

The implication is that when athletes select their own pace, a constant effort can be maintained despite high lactate concentrations. This raises serious doubts not just over whether 4mmol/L can be regarded as the lactate threshold point but whether the concept of a lactate threshold is relevant to athletic performance. It may be that the long-term accumulation of lactate during a race or time trial is much higher than the levels found during incremental tests in the laboratory, which questions the validity of lab-based lactate testing as a way of predicting performance.

The study found a wide degree of variation in lactate concentrations between athletes. Since there was no correlation between lactate concentration and performance, this suggests a link with individual muscle fibre type. For example, an athlete with a greater proportion of type IIa fibres will produce more lactate than one with more type I fibres, even with identical performances.

So is there any point in lactate testing? Certainly the observed variations in concen-trations that can be maintained for long periods would cast doubt on its use for predicting performance. And there may be little association between lactate found in the lab and that found in competition conditions.

Lactate testing may need to be restricted to individual longitudinal tests at a fixed workloads. For example, testing the lactate response to a 20-minute run at 12kph would be an objective measure of aerobic fitness for an individual athlete which, if repeated regularly, could be used to determine training status and assess the effects of a training programme on the aerobic system.

Medicine and Science in Sport and Exercise 33(1), 152-156

Raph Brandon