Measuring Glycolytic Capacity

Increasing the ability to perform repeated muscular actions for an extended duration of time is a goal of many training programs. Endurance performance is largely explained by three key factors: aerobic capacity, lactate threshold, and work economy. A great deal of research has therefore been devoted to the study of changes in measures in these areas in response to different interventions. However, anaerobic components of fitness can also provide a large contribution to endurance performance. Collectively, these components of aerobic fitness are often referred to as anaerobic capacity.

The term anaerobic capacity encompasses the capacity of the ATP-CP system and the capacity of the glycolytic energy system. The ATP-CP system is a simple energy system that functions to maintain Adenosine Triphosphate (ATP) levels. The glycolytic system produces energy through glycolysis, which is the breakdown of glucose to pyruvic acid. As such, glycolytic capacity refers to the capacity to generate energy from the metabolism of glucose. Exercise scientists have developed many ways of measuring these variables and each has strengths and weaknesses, as well as different degrees of accuracy.

What does this page provide?

This page explains what methods for studying changes in lactate threshold are available, when they are used, why they are used, and how accurate they are. By the end, you will be able to critically appraise studies investigating these areas and understand their individual strengths and weaknesses.

Identifying key concepts - measuring glycolytic capacity

The following terms and concepts are key for an understanding of how glycolytic capacity has been measured:

1. 60 second run test – this involves running for 60 seconds on a treadmill that is set to a 4% grade incline and a speed of 22 km/h, or 20 km/h for females. Blood samples are taken before and after the test, with the idea being that as athletes get closer to competing they should accumulate less lactate in response to the test.

2. Blood lactate – this is the content of lactate in the blood and is the balance between muscle lactate production and lactate clearance.

3. Maximal Accumulated Oxygen Deficit (MAOD) – this is a measure of anaerobic capacity and is based on the numerical difference between the total energy demand of a severe exercise bout and the energy portion associated to the total oxygen consumption.

4. Repeated Sprint Ability (RSA) – this is the ability to perform repeated short, maximal effort, sprints with short brief recovery periods between bouts.

5. Wingate test – this is a 30 second maximal effort cycling ergometry test devised to be a means of testing for power and anaerobic capacity.

MEASURING GLYCOLYTIC CAPACITY

Peak lactate readings have been used to measure glycolytic capacity following maximal exercise tests as an indirect measure of anaerobic energy provision. Indeed, peak blood lactate readings do tend to increase following anaerobic training (Jones, 2007). However, this is an indirect measure, because blood lactate levels represent a balance between muscle lactate production and lactate clearance. As a result of this, improved glycolytic capacity may result in a higher lactate reading but other processes can also affect the result. For example, the ability to clear lactate quickly once it has been produced may lead to lower-than-expected readings. Such quick clearance may in fact arise from a very large aerobic capacity leading to a very efficient clearance process. Indeed, there are examples in the literature of world-class endurance athletes displaying very low values for peak blood lactate following maximal testing procedures (Coyle, 2005; Jones, 2006). This does suggest that aerobic capacity can have a strong influence on peak blood lactate values, perhaps by improving the rate of clearance.

The Fatigue Index

As an alternative to using peak lactate readings, it has been proposed that tests of anaerobic fitness should involve several metrics, including: a maximum score, a mean value and a fatigue index (Tong & Wiltshire, 2007). The fatigue index represents the difference between the maximum value achieved during a maximal effort test and the minimum value achieved at the end. A smaller difference between the two values is indicative of greater resistance to fatigue. Improved fitness levels would be expected to result in a smaller fatigue index. However, once again, it is not possible to differentiate between aerobic and anaerobic processes and their relative contributions towards improved scores.

Wingate test

The Wingate test is a 30 second maximal effort cycling ergometry test devised to be a means of testing for power and anaerobic capacity (Inbar et al., 1996). Four main variables can be determined from the results of a Wingate test. These are: Peak Power Output, Relative Peak Power Output, Anaerobic Capacity and Fatigue Index. Peak Power Output usually refers to the maximum power achieved in the first five seconds of the test. Relative Power Output is determined by dividing Peak Power Output by Body Mass. Anaerobic Capacity is the term used to describe the mean power output achieved for the whole test and fatigue index is used to describe the decline in power. By providing a maximum score, mean value and a fatigue index, this test meets the requirements for an anaerobic test of fitness proposed by Tong & Wiltshire (2007). However, it is not possible to determine the relative contribution of aerobic and aerobic processes towards the improvement of scores in this test.

60 second run test

This test involves running for 60 seconds on a treadmill that is set to a 4% grade incline and a speed of 22 km/h, or 20 km/h for females. Blood samples are taken before and after the test, with the idea being that as athletes get closer to competing they should accumulate less lactate in response to the test (Australian Institute of Sport, 2013). While a 60 second run test is likely to heavily involve the glycolytic system, this methodology is problematic as a proxy measure of glycolytic capacity. This is because increased glycolytic capacity is usually associated with elevated lactate readings. Of course, this only applies in response to maximal testing procedures. However, a decrease in the accumulation of lactate in response to a submaximal test could be attributable to increased aerobic fitness. Alternatively, it could be attributable to increased levels of maximal sprint speed, meaning that this absolute sub-maximal running speed now represents a decrease in relative intensity. However, it seems difficult to directly attribute a decrease in lactate readings to increased glycolytic capacity.

A variation of the 60 second run test is to require the athlete to continue to exhaustion (Jones, 2007). In this situation, as athletes get closer to competition they should be able to continue for longer. They might also be expected to accumulate more lactate in response to the test. This therefore seems more appropriate as a proxy marker for glycolytic capacity.

Repeated Sprint Ability (RSA) tests

A large number of Repeated Sprint Ability (RSA) tests have been reported in the literature. A common feature of these tests is that they involve repeated short, maximal effort, sprints with short brief recovery periods between bouts. It is usual for these tests to measure and record three separate variables. These are the best sprint score achieved in any single effort in the test, the mean sprint time for all the sprints performed in the test and the fatigue index. The fatigue index is usually measured in terms of the difference between the best and the worst score in the test. Mean sprint scores have been shown to have much smaller coefficients of variation and error values compared to fatigue index scores (Oliver, 2009; Spencer et al., 2006). As a result, the value of fatigue index scores has been questioned, and mean sprint score is currently considered to be the primary measurement in a RSA test (Dawson, 2012). The drawback of using mean sprint score as a proxy measure of glycolytic capacity is that it is not possible to determine the relative contribution of aerobic and anaerobic processes towards improved scores. This is a limitation that is common to all performance based field tests.

Maximal Accumulated Oxygen Deficit (MAOD)

The Maximal Accumulated Oxygen Deficit (MAOD) is considered as one of the best measures of anaerobic capacity. It is based on the numerical difference between the total energy demand of a severe exercise bout and the energy portion associated to the total oxygen consumption (Nakamura & Franchini, 2006).

To determine MAOD in an individual, first a linear relationship between work rate and oxygen uptake needs to be established for that individual. This can be done by obtaining measurements of oxygen uptake at a range of different exercise intensities. Once this has been done, the relationship between work rate and oxygen uptake needs to be extrapolated to exercise intensities that are supra-maximal to VO2-max. Clearly oxygen uptake will not actually increase at these supra-maximal intensities. However, this extrapolation allows the VO2 demand corresponding to supra-maximal workloads to be predicted. When this VO2 demand is multiplied by the duration of an exercise bout, the accumulated VO2 demand can be estimated. The maximal accumulated oxygen deficit can then be calculated by subtracting the accumulated oxygen uptake, measured during the exercise bout, from the estimated accumulated VO2 demand (Noordhof et al., 2010).

Validity and Reliability of Measurements

The validity and reliability of the use of the MAOD as a measure of anaerobic capacity has been subject to investigation. The validity of this method has been assessed by comparing measurements with the metabolic measurement of anaerobic adenosine triphosphate production. However, the accuracy of this method of comparison has been questioned (Noordhof et al., 2010) and so it is difficult to draw firm conclusions from findings relating the validity of MAOD measurements. Furthermore, research into the reliability of this method suggests that it is not a reliable measure of anaerobic capacity (Noordhof et al., 2010). As such, measurement of the MAOD may be considered as a non-invasive alternative to the use of blood lactate readings. However, caution is advised in the interpretation of findings from these measurements.

Respiratory Exchange Ratio

The Respiratory Exchange Ratio (RER) was originally used to determine the anaerobic threshold. The RER is the ratio of carbon dioxide production to oxygen consumption, and so an increase level of carbon dioxide production would be expected to result in an increased RER. However, this method is now outdated. Current best practice for the determination of Anaerobic Threshold is the identification of the point at which the ventilatory equivalent for oxygen shows a sudden increase while the ventilatory equivalent for carbon dioxide remains relatively stable. The ventilatory equivalent for oxygen is the ratio of ventilation to oxygen consumption. Similarly, the ventilatory equivalent for carbon dioxide is the ratio of ventilation to carbon dioxide produced. The increase in the ventilatory equivalent for oxygen indicates that the increase in ventilation to remove carbon dioxide is disproportionate to the body’s need to provide oxygen.

When Anaerobic Threshold is determined in this way, it seems to occur at the same time point as Lactate Threshold during incremental exercise tests. As such it may be thought of as a useful non-invasive estimate of Lactate Threshold. Furthermore, in certain populations and under certain conditions a test of Anaerobic Threshold should actually be used in favour of Lactate Threshold. For example, individuals with McArdle’s disease are unable to increase blood lactate and Hydrogen ion levels during exercise. A clear anaerobic threshold can be determined in these individuals but the measurement of Lactate Threshold is not possible as blood lactate remains at resting levels.

SUMMARY - Measuring Glycolytic Capacity

Direct assessment of glycolytic capacity is very difficult. This is because current tests that have been devised to measure glycolytic energy provision are either surrogate markers only capable of providing estimations or are subject to great potential for error. Peak lactate readings have been used following maximal exercise tests as an indirect measure of anaerobic energy provision. However, blood lactate represents the balance between muscle lactate production and lactate clearance. As a result of this, while improved glycolytic capacity may result in a higher blood lactate reading, other processes (including probably aerobic capacity) will also affect the result.

Instead of using blood lactate readings, it has been proposed that glycolytic capacity should be measured using a combination of several metrics, including: a maximum score, a mean value and a fatigue index. The primary examples of tests that include these metrics are the Wingate test and RSA tests. However, a large degree of error is associated with measurements of fatigue index. As such, mean values of performance or power output are considered to be the primary measurement in these types of test. The drawback of using mean scores as proxy measures of glycolytic capacity is that it is not possible to determine the relative contribution of aerobic and anaerobic processes towards improved scores. This is a limitation that is common to all performance-based field tests. Glycolytic capacity can also be measured using the MAOD but current methods do not produce reliable measurements and there are difficulties associated with determining its validity. As a result of the numerous problems in determining glycolytic capacity, it is wise to be cautious in interpreting findings in the literature in this regard.

References - Measuring Glycolytic Capacity

Coyle, E. F. (2005). ‘Improved muscular efficiency displayed as Tour de France champion matures’. Journal of Applied Physiology, 98, pp. 2191-6
2. Jones, A. M. (2006). ‘The physiology of the world record holder for the women’s marathon’. International Journal of Sports Science and Coaching, 1 (2), pp. 101-16
3. Jones, A. M. (2007). Middle and long distance running. In: Winter, E. M., Jones, A. M., Davison, R., Bromley, P. D. & Mercer, T. H. (2007). Sport and Exercise Physiology Testing Guidelines. London: Routledge
4. Tong, R. J. and Wiltshire, H. D. (2007). Rugby Union. In: Winter, E. M., Jones, A. M., Davison, R., Bromley, P. D. and Mercer, T. H. (2007). Sport and Exercise Physiology Testing Guidelines. London: Routledge
5. Inbar, O., Bar-Or, O. & Skinner, J. S. (1996). The Wingate Anaerobic Test. Champaign, Illinois: Human Kinetics
6. Tong, R. J. and Wiltshire, H. D. (2007). Rugby Union. In: Winter, E. M., Jones, A. M., Davison, R., Bromley, P. D. and Mercer, T. H. (2007). Sport and Exercise Physiology Testing Guidelines. London: Routledge
7. Australian Institute of Sport (2013). ‘Physiological Tests for Elite Athletes. Champaign, Illinois: Human Kinetics
8. Jones, A. M. (2007). Middle and long distance running. In: Winter, E. M., Jones, A. M., Davison, R., Bromley, P. D. & Mercer, T. H. (2007). Sport and Exercise Physiology Testing Guidelines. London: Routledge
9. Dawson, B. (2012). ‘Repeated-sprint ability: where are we?’. International Journal of Sports Physiology and Performance, 7, pp. 285-9

Further References - Measuring Glycolytic Capacity

10. Oliver, J. (2009). ‘Is a fatigue index a worthwhile measure of repeated sprint ability’. Journal of Science and Medicine in Sport, 12, pp. 20-3
11. Spencer, M., Fitzsimons, M., Dawson, B., Bishop D. and Goodman, C. (2006). ‘Reliability of a repeated sprint test for field hockey’. Journal of Science and Medicine in Sport, 9, pp. 181-4
12. Nakamura, F. Y. and Franchini, E. (2006). ‘Maximal accumulated oxygen deficit as a predictor of anaerobic capacity’. Brazilian Journal of Kinanthropometry, 8, pp. 88-95
13. Noordhof, D. A., de Koning, J. J. & Foster, C. (2010). ‘The maximal accumulated oxygen deficit method: a valid and reliable measure of anaerobic capacity?’. Sports Medicine, 40 (4), pp. 285-302
14. Jones, A. M., Carter, H. & Doust, J. H. (1999). ‘A disproportionate increase in VO2 coincident with lactate threshold during treadmill exercise’. Medicine and Science in Sports And Exercise, 31, pp. 1299–306

15. Jones, A. (2006). ‘The physiology of the world record holder for the womens marathon’. International Journal of Sports Science and Coaching, 1 (2), pp. 101-16
16. Pringle, J. S. M. and Jones, A. M. (2002). ‘Maximal lactate steady state, critical power and EMG during cycling’. European Journal of Applied Physiology, 88 (3), pp. 214-26
17. Smith, C. G. and Jones, A. M. (2001). ‘The relationship between critical velocity, maximal lactate steady-state velocity and lactate turnpoint velocity in runners’. European Journal of Applied Physiology, 85, pp. 19-26
18. Amman, M., Subudhi, A. W. & Foster, C. (2006). ‘Predictive validity of ventilatory and lactate thresholds for cycling time trial performance’. Scandinavian Journal of Medicine and Science in Sports, 16 (1), pp. 27-34

Additional Notes

This resource page on measuring glycolytic capacity was produced by Tim Egerton whilst working on a previous project. It is unlikely that further updates to this resource page will be produced. This is because Tim is now primarily focused on Foxwood Personal Training in York. There are three primary services for Foxwood Personal Training. You can find out more about these in the following links:

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Egerton's Garage Gym, York

Whilst the Online Running coaching listed above is of course delivered remotely, the other services are delivered in person. Specifically, the Personal Training and Sports Massage services both take place at Egerton’s Garage Gym. So if you are based in York, then you may be interested to lean more about Egerton’s Garage Gym (The EGG).

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