In part 1, we discovered the ‘blood lactate’ story. My own journey in learning more about lactate began over a decade ago, but it was a meeting in 2006, when I conducted an interview Dr. Inigo San Millan, that really piqued my interest in the subject. Dr. Inigo is now a professor at the University of Colorado School of Medicine, but 8 years ago he was working as a team doctor in professional cycling. His view on the the use of blood lactate to inform training was emphatic:

“We try to organize training in the most scientific way possible. Lactate is the most important parameter for us. VO2 max. is significant, but it is more an indicator of cardiorespiratory adaptation. At this level, most riders will have developed this to its maximum capacity. Whereas lactate tells us more about what is going on inside the muscle cell, how efficient a rider is and provides a better parameter to prescribe appropriate training.” Dr. Inigo San Millan 

Practically, how could you use an understanding of lactate to improve your cycling performance? Because research has helped us to understand the role of blood lactate in energy metabolism, measuring blood lactate during exercise provides an insight into how your body is using fuel.

Whilst there isn’t a one-to-one relationship between lactate in the muscle and lactate in the blood, measuring blood lactate concentration provides an “indirect yet reproducible indication of the aerobic capacity of the working muscles” (Spurway & Jones, 2007). Ideally, a cyclist would undertake some kind of physiological testing, such as an incremental test, to measure their blood lactate response to increasing exercise intensity and determine individual thresholds and training zones. By re-testing during different phases of training and racing, it is possible to assess changes in aerobic fitness.

Lactate Threshold

The concept of ‘lactate threshold’ is generally confused and poorly understand, largely because of the wide range of terminology used to describe blood lactate response to exercise. I could dedicate an entire post to this subject (and I may at some point), but to try to keep things simple, I’ll stick to the terminology recommended by the the British Association of Sport and Exercise Sciences (BASES).

In a typical test protocol designed to assess a cyclist’s blood lactate response to exercise, the subject would ride on an bicycle ergometer or even in the field (though this is much more difficult to control). The test would begin at an intensity equivalent to around 40% VO2 max (zone 1 of a 6 zone system). The work rate would be increased by 20-50 watts every 4 minutes until the subject reached exhaustion. There should be a minimum of 5 and a maximum of 9 stages. At the end of each 4 minute stage, the tester would take a small drop of blood, generally from the finger tip or ear lobe, and use a device such as a lactate pro 2 to measure the blood lactate concentration.

At the end of the test, the tester would create a graph to plot blood lactate concentration (measured in millimoles) relative to exercise intensity, (measured in watts). This graph could then be analysed to determine the subject’s threshold intensities.

Lactate profile chalkboard

At the beginning of the test, blood lactate is typically at a baseline value of around 1mmol. As work rate increases, blood lactate concentration will begin to rise. This first rise above the baseline value  represents a ‘break-point’ called ‘lactate threshold’. After this initial rise, exercise intensity continues to increases but blood lactate concentration generally stabilises for a period of time. There may even be a slight drop in blood lactate concentration. Lactate formation is still increasing during this time, but lactate concentration in the blood remains relatively stable because lactate is being cleared as quickly as it is formed: imagine bailing out a boat. However, at some point, the rate of lactate formation exceeds the rate of removal. In the test, this will be seen as a second sudden and sustained increase in blood lactate. This point is known as ‘Lactate Turnpoint’. This point also provides a good approximation of the work rate which is sometimes described as ‘Maximal Lactate Steady State’ (Smith & Jones, 2001). MLSS represents the maximum intensity at which there is an equilibrium between lactate formation and clearance. In an ideal 1-hour time-trial or climb (if you were fresh), your power output at MLSS would be a good target wattage to elicit your best performance. If a training programme was effective, we would expect to see that power output at Lactate Threshold and Lactate Turnpoint would increase. This would be illustrated on the graph by a rightward shift in the blood lactate curve.

Lactate comparison chalkboard

Lactate & Training Zones

Lactate threshold and lactate turnpoint can also be used to prescribe very specific, individualised training zones. Training zones are useful because they prescribe an exercise intensity which is designed to send a signal to elicit an adaptation in a particular energy system.

“Training periods should be designed to emphasise the stress on a particular cellular process, to provide the optimum signal and drive adaptation.” James Hewitt 

ATP resynthesis

Training zones based on a percentage of threshold power are a useful and practical means to prescribe training intensity. However, these percentages are based on broad averages in terms of how cell metabolism responds to increasing exercise intensity. In reality, there is quite a wide range of individual difference. Practically, this means that the ‘signal’ my body receives from exercising at 60% of my highest 60 minute average power output may be ‘louder’ or ‘quieter’ than the signal that your body receives from the same percentage intensity.

Monitoring blood lactate response helps us to understand how ‘loud’ the signal is for an individual relative to different exercise intensities and allows us to prescribe training zones more accurately. The most stark examples of this is in an approach to training intensity distribution called ‘polarised’ training

Read more about polarized training in part 3:


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