Lactate testing for sports anno 2022

Lactate testing becomes increasingly interesting once you understand the full mechanism behind it. Fortunately, more and more coaches and athletes understand what lactate is NOT: a waste product. Now it’s time to make sure you fully understand what it is! This article covers everything you need to know about lactate and lactate testing. Let’s get started!

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This article contains everything you need to know about lactate testing. There is also a free education course included, which fully focuses on how to actually take blood samples for lactate testing. Fill in the form to start the e-course or begin with reading the article below.

Table of Contents - article

Before we can learn more about lactate testing, we need to know what lactate actually is.


To fully understand what lactate is, we need to look at our energy systems. Energy systems need fuel to produce energy. One of those fuels is carbohydrate.

The process of using carbohydrates as a fuel starts in the glycolytic (anaerobic) energy system. This energy system uses glucose (carbohydrates) to produce energy. The end product of this process is lactate! In other words: lactate is the end product of the glycolysis.

Lactate is always the end product of glycolysis

Does lactate cause fatigue?

When exercise intensity increases, athletes start to use more carbohydrates as a fuel. As a result, more lactate is produced. This is one of the reasons why people used to think lactate is a by-product that causes fatigue: at high exercise intensities, lactate concentrations are high, and athletes fatigue. However, there is no causal relationship between lactate and fatigue.

Lactate is NOT causing fatigue, it’s not even a “waste product”. It’s a FUEL!

We’ve seen that the anaerobic energy system produces lactate. The aerobic energy system uses this lactate as a fuel to produce even more energy:

Carbohydrate and fat energy metabolism
The glycolytic energy system uses glucose and produces lactate


There are many reasons why measuring lactate values is interesting for athletes and coaches. Let’s look at some examples.

Lactate: a marker for glycolytic activity

We learned that lactate is always the end product of glycolysis (also called: anaerobic energy system). Therefore, the lactate production rate tells you something about how active the anaerobic energy system is. The maximal lactate production rate is often called VLamax.

Measuring lactate to understand the anaerobic energy system better is like measuring oxygen to understand the aerobic energy system better. That’s why we often call the VLamax a brother of the well-known VO2max.

Lactate: a marker for fatigue

We’ve learned that lactate does not cause fatigue. However, blood lactate concentrations are a good marker for fatigue. For instance, when an athlete shows an ongoing increase in lactate concentration, you can be pretty sure that he/she will fatigue.

Lactate production vs Lactate combustion
Lactate production (red) is a marker for glycolytic activity. Lactate concentration (yellow) is a marker for fatigue.

Lactate: a marker for carbohydrate utilization

Finally, since all carbohydrates “pass” the anaerobic energy system, knowing the lactate production rate also tells you something about the carbohydrate utilization. It should therefore come as no surprise that the lactate production curve looks similar to the carbohydrate combustion curve.

Fat and carbohydrate combustion in running
When intensity increases, carbohydrate combustion increases (and therefore lactate production).

There is one catch though. Lactate production occurs in the muscle. Ideally you could stick a needle into the muscle and measure it. This is practically impossible.

It’s actually similar to measuring VO2. Ideally you would measure this in the mitochondria of the muscle, but again, this is practically impossible.

For VO2 measurements, you often use a metabolic cart that captures air flow via a mouth mask. For lactate measurements you use blood lactate samples.

Even though these are well accepted alternatives to sticking a needly into a muscle, it’s still important to not mistake lactate production in the muscle (local) with lactate concentration in the blood (whole body)! We will talk about that later, but let’s first look at how you can actually take blood lactate samples.


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Topics covered:

  • Should you take lactate samples in the earlobe or in the finger?
  • Which lancet should you use?
  • Do’s like: cleaning
  • Don’t like: squeezing
  • And more..

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We now know what lactate is, why we should measure it, and how to actually take valid lactate samples. But what should our athlete do during the test? In other words, what is a good lactate testing protocol?

Exercise intensity and blood lactate values

Blood lactate concentration changes with exercise intensity. At higher exercise intensities you eventually get higher blood lactate values.

Exercise duration and blood lactate values

Blood lactate concentration can also change in time. Even when exercise intensity remains the same. Imagine for example an athlete who runs a 10k. The running pace will roughly stay the same. However, the lactate concentration at the finish will be higher than the lactate concentration halfway through the race. In other words: the lactate concentration increases even though the pace is constant.

Lactate concentrations depend on time and intensity. Every individual will react differently to these two factors. So if you want to learn how your athlete responds to exercise, it hopefully makes sense to use different durations and different exercise intensities in your lactate testing protocol.

Hopefully it also makes clear that you can’t compare the results of two different (duration and/or intensity) ramp- or step protocols.

Although INSCYD users can create their own protocol, we also provide you with a lactate test example protocol. This protocol meets all the requirements. Request the lactate test protocol here:


Now that we have our blood lactate test results, what should we do with it? First we need to fully understand what we are looking at.

As I briefly mentioned before, we got to keep in mind that blood lactate measurements are a practical alternative of what we really want to measure: lactate production in the muscle.

Also: blood lactate concentrations are a result of lactate production and lactate “combustion”. We’ve learned that the glycolytic (anaerobic) energy system produces lactate. We’ve also learned that the aerobic energy system uses this lactate as an energy source.

“Lactate concentration is the product of lactate production and lactate combustion.”

Regardless of the exercise intensity: there is always a lactate production. There is also always a lactate combustion.

Lactate production vs Lactate combustion
There is always a lactate production (red) and a lactate combustion (blue).

Without any further analyses, the blood lactate concentration does not give you any precise information about the lactate production rate. It also does not give you any precise information about the lactate combustion rate.

Only if you used a wide variety of durations and intensities, you can start separating production and combustion from each other. This is where INSCYD comes in handy. It helps you to get valuable information out of your lactate data. Learn more about INSCYD via the buttons:

Lactate dilution space

There is another thing we should take into account when analyzing our blood lactate test results. That is body composition.

We all know VO2max is often expressed in oxygen uptake per kg bodyweight. But did you notice that lactate concentrations are expressed in mmol per liter? You might wonder: which liters?

As always when looking at concentrations, you have to take into account:

  1. The amount of solute: the component itself. In this case the amount of lactate expressed in mmol.
  2. The amount of solvent: the dilution space. In this case the lactate dilution space expressed in liters.

Lactate is water-soluble. It exists in parts of the body that contain water. Therefore it is important to understand something about the amount of water in an individual body.

Lactate production and dilution space
The lactate dilution space differs per person and has an effect on the lactate concentration.

Let me give you an example. Imagine you test a tall athlete with a low body fat percentage. In other words: an athlete with a high lactate dilution space (lactate does not dissolve in fat).

You put your athlete on a stationary bike and the leg muscles start to produce a significant amount of lactate, resulting in a lactate concentration of 4 mmol per liter.

Now I want you to imagine you put the exact same leg muscles in a smaller person with a higher fat percentage. In other words: image the same leg muscles in an athlete with a lower lactate dilution space. What will the lactate concentration be?

The exact same muscles will produce the exact same amount of lactate, but you will measure a blood lactate concentration above the previously measured 4 mmol per liter.

In other words, body composition is part of your lactate test result. This matters when:

  • comparing results between individuals with a different body composition;
  • comparing results within an individual who is changing body composition (e.g. losing weight).

It goes without saying that the difference in body composition of men and women must also be taken into account. On average, women have a higher body fat percentage than men. Since lactate does not dilute in fat, having a higher fat percentage decreases lactate dilution space.

With INSCYD, you can easily take the lactate dilution space into account.

Lactate testing software: connecting the dots

Now that we fully understand the principles around lactate, it’s time to use the data and get a full metabolic report. This is where a software tool like INSCYD can help a lot. It turns lactate data into usable metrics like: VO2max, VLamax, FatMax, and many more. INSCYD graphs can show you: carbohydrate combustion, lactate accumulation rates, recovery time and many more.

Learn more about INSCYD via the article: What is INSCYD or schedule a demo to ask your personal question!