VLamax – Theoretical background and how it determines your FTP

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Where VO2max tells you something about your endurance, VLamax is about your sprint. But there is more! Recently, there has been a lot of talk about VLamax and tests that allow you to measure it. Although the concept is actually not that difficult, most people do not know what VLamax is or how they can use it in their training or coaching. In this article we will try to get you up to speed!

3 energy systems

First, we have to quickly revisit some theory about energy metabolism that some of you are already familiar with, but that is needed to fully grasp the concept of VLamax.

Roughly speaking, you could say that there are 3 main systems in the human body that can deliver energy to your muscles: The ATP-PCr, glycolytic and aerobic systems. In the chart below the relative contribution from each of these systems is shown.

Source: Gastin, P. B. (2001). Energy system interaction and relative contribution during maximal exercise. Sports medicine, 31(10), 725-741.

From this chart you can conclude that for very short exercise bouts (i.e. very high intensity or power), ATP-PCr is contributing the most energy. After that and until about 1 minute the glycolytic system delivers the majority of the energy. And after that the aerobic system takes over.

Please note that although after about 1 minute the aerobic system is highest, the glycolytic system is still very active and its contribution still significant. Also, the glycolytic system produces lactate while it is active, while the other 2 systems do not, and this means that even at lower intensities lactate is produced. Keep this in mind while you keep on reading.


Source: https://en.wikipedia.org/wiki/Metabolic_pathway

We will not bother you with all the metabolic pathways in a human body but we want to highlight 1 important thing that is needed to understand VLamax: Pyruvic acid (or “pyruvate”) plays a role and is a limiter in both the lactate shuttle (the process that clears lactate from you muscle and transforms it into a substrate that can be used for aerobic energy delivery) and fatty acid oxidation. In other words: you need pyruvate to clear lactate and to burn fat.

Pyruvate availability seems to increase linearly with your VO2 (i.e. at lower intensities it is lower than at higher intensities) and pyruvate demand for the lactate shuttle takes precedence over fatty acid oxidation (i.e. if there is pyruvate demand for the lactate shuttle it will be used for that and not for fatty acid oxidation).

Balancing lactate production and combustion

All this information can be combined to draw a picture of the lactate balance in your body.

The red line is the lactate production from your glycolytic system. The blue line is the lactate combustion capacity as made possible by pyruvate availability. As mentioned before, lactate combustion has a linear relationship with your oxygen consumption (VO2), explaining why it levels off at higher intensities (i.e. your VO2max). The point at which the red and blue lines intersect (the point at which lactate production is equal to the lactate combustion capacity) is your anaerobic threshold. Intensities above this threshold will result in a significant increase in blood lactate concentration and eventually exhaustion.

The gray area in the chart above represents the pyruvate capacity that is available for fatty acid oxidation. In the chart below this pyruvate capacity is plotted, showing a maximum at FatMax.


You might think: “This is all very interesting, but how does this relate to VLamax?”. Well, we arrived at the point where we can explain it!

VLamax is the maximum rate of lactate production and can be seen as the maximum slope of the lactate production line in the plot above. VLamax is not that interesting in itself, but it is a good indicator of your lactate production at intensities below VLamax: A high VLamax indicates that even at lower intensities your lactate production might be relatively high. And a low VLamax indicates that your lactate production stays low even at higher intensities. This information is very interesting because it can be used, as you have seen above, to determine e.g. your FatMax and anaerobic threshold.

One final remark before we end this blog: A high VLamax is not good or bad. It is merely a tool to describe your energy metabolism at different intensities. For a sprinter a high VLamax (anaerobic power) is good, at the cost of a lower anaerobic threshold, for a time trialist a low VLamax might be good, at the cost of a lower maximum anaerobic power.

In a following blog, Loek will talk about how knowing your VLamax can be used for your training.

Measure your VLamax yourself

Our interest in VLamax was the start of a collaboration between Molab and INSCYD. If you want to know your VLamax, you can buy the INSCYD Power-Performance Decoder test via our webshop and we will help you in performing the test and interpreting the results. The only thing you need is a smart trainer (at home or in your local gym) or a power meter. Feel free to ask any question via contact.

Want to know more about the INSCYD Power-Performance Decoder test? Read our review here, or buy the test!

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