Running performance is a complex interaction of multiple factors, so how do we measure it, and how do we use the data to improve performance in the real world? Typically, running performance is measured using three major factors that can be assessed in a lab setting; VO2max, Lactate threshold and running economy.
The first factor, VO2max, is a measure of aerobic exercise capacity1. It is defined as the maximum amount of oxygen that the body can utilise during exercise, and is measured in millilitres of oxygen consumed per minute per kilogram of body weight (mL/kg/min). One can increase your VO2max with training, and thus a higher post-training value when compared with pre-training indicates an adaptation of greater aerobic exercise capacity. VO2max Testing becomes important when designing a training programme for someone who has not run any races and who therefore has no race times2. In this case, a VO2max test will give an indication of the current ability of the athlete on which to base training schedules. Additionally, if VO2max testing is done regularly, it can provide information as to how effective a training programme is. It is a myth that your VO2max is a set value determined by genetics, it is trainable, but it may have genetically determined upper limit.
The second factor, lactate threshold, is defined as the exercise intensity and/or blood lactate concentration at which, one can only sustain a high intensity effort for a specific period of time4. The lactate threshold conceptdefines the point at which metabolic acidosis and the associated changes in gas exchange in the lungs, occur during exercise3. This is a result of the rate of lactate accumulation in the muscles exceeding that of lactate removal. A higher lactate threshold will therefore indicate improved performance, i.e. the ability to sustain higher levels of exercise intensity for a longer duration of time.
It might surprise you that lactic acid does not exist as an acid in the body but rather as lactate, and it is this that is actually measured in the blood when lactate threshold is determined5. It is also a myth that lactic acid is the cause of the stiffness felt after an event such as a marathon. Stiffness is due mostly to muscle damage and not an accumulation of lactic acid in the muscle5. It might also be a surprise that lactate does not actually cause fatigue, but rather the hydrogen ions associated with it do; lactate is actually an important fuel that is used by the muscles during prolonged exercise5. Lactate released from the muscle is converted in the liver to glucose, which is then used as an energy source. So rather than cause fatigue, it actually helps to delay a possible lowering of blood glucose concentration, a condition called hypoglycaemia, which will cause a runner to feel weak and fatigued if it occurs5.
The final factor, running economy, is represented by the steady state energy demands associated with running at a certain submaximal speed, and is expressed as a submaximal VO2 at that given running speed6-8. It is also often expressed as the oxygen cost to run 1 km, in ml/kg/km. Amongst runners with similar VO2max values, running economy may differ by as much as 30%, and is therefore able to distinguish between faster and slower finishers9. Factors affecting running economy include genetics, metabolic efficiency, cardiorespiratory efficiency, biomechanical efficiency, neuromuscular efficiency and training6-8. To put it simply, running economy is the measure of the efficiency of movement, and the greater your running economy, the less energy you use to run at a given speed. The percentage of VO2max (% VO2max) is an expression of performance that incorporates both running economy and VO2max. At a given velocity each individual runner will be at a different % of their VO2max and vice versa.
These three factors are used independently and together to measure running performance. However, the best measure of performance is still a simple time trial or a race as this type of test simulates the real world application of all three factors.
Read more about the SSISA GRIT Team here. To read more about the Health through Physical Activity, Lifestyle and Research Centre, Division of Physiological Sciences at the University of Cape Town, please see the HPALS website or email Ayesha Hendricks for more information about applications for MSc/PhD research programmes.
To get in touch with the Sports Science Institute of South Africa Group for Research Implementation and Translation (GRIT) Research Consultants, get in touch with Warren Lucas at research@ssisa.com or call 021 650 5728 for enquiries.
Yours in Sports Science,
Sports Science Institute of South Africa
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