[Ultimate Guide] Lactate Testing in Sports – Unlock Athlete Performance

Lactate testing becomes increasingly interesting once you fully understand how lactate behaves and which conclusions you can draw from a lactate test. This article covers everything you need to know about lactate and lactate testing. Included: 5 practical do-it-yourself steps for lactate testing. Let’s get started!

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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
INSCYD Graph: 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
INSCYD Graph: 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 face mask. For lactate measurements you use blood lactate samples.

Metabolic Testing Mask
INSCYD lactate test Alpecin Fenix
Lactate Testing

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 the 5 steps you need to take to perform a lactate test.

Step 1: buy a lactate testing kit


Before you can start performing lactate threshold tests, you need a lactate testing kit. Your lactate testing kit should contain:

  • Lactate meter:
    • Portable handheld lactate monitor or;
    • Table-top lab lactate analyzer
  • Lactate test strips or capillary
  • Lancets
  • Disposable gloves
  • Disinfectant like alcohol
  • Swab

To perform an actual lactate threshold test, you also need an exercise setup. Although lactate testing is ideal for outdoor field tests, you can also use a treadmill or indoor bike trainer. Lastly, you need something to define exercise intensity. This could be a speed/pace tracker (e.g. GPS watch or stopwatch), heart rate monitor or power meter.

Which lactate meter should I buy?

There are several blood lactate meters available on the market, but which is the best lactate meter?

Lactate Pro 2
Lactate scout 4
  1. Lactate Pro
  2. Lactate Pro 2
  3. Lactate Scout+
  4. Xpress
  5. Edge
  6. i-STAT

They concluded that both the Edge and Xpress lactate meters had low total error for lactate concentrations below 15 mmol/L, whereas the Edge and Lactate Pro 2 were the better of the portable analysers for concentrations above 15 mmol/L.

Another scientific study compared the reliability and accuracy of the Lactate Pro, Lactate Scout and Lactate Plus. This study showed that the Lactate Pro and Lactate Plus displayed good reliability and accuracy when compared to a laboratory-based analyser. The Lactate Scout also displayed relatively good reliability, but it was not as reliable or accurate as the other two.

However, both studies are a bit outdated by now.

To give you an idea, the Lactate Scout 4 claims to have the following imprecisions:

  • Below 6.7 mmol/L: ≤ 0.2 mmol/L
  • Above 6.8 mmol/L: ≤ 3%

Keep in mind that even the best blood lactate monitor gives useless results when blood lactate samples are taken wrong. Keep reading for a guide to taking valid lactate samples.


We now know what lactate is, why we should measure it, and what lactate testing kit to buy. But what should 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 coaches and labs can create their own protocol, we also provide you with a lactate test example protocol. This protocol meets all the requirements.

INSCYD allows you to create a lactate test protocol that suits your needs. This is one example, using different time durations and exercise intensities.

Learn more about all INSCYD test protocols and request the INSCYD lactate test protocol here:

Request lactate test protocol


Want to become a pro in lactate testing? Start our free e-learning course: The complete guide to taking valid lactate samples.

To start the e learning course: press start!

Free Course to Taking Valid Lactate Samples

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..
Play: Lactate course preview

The Complete Guide to Taking Valid Lactate Samples

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..


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 athlete performance analytics comes in handy. It helps you to get valuable information out of your lactate data.

INSCYD enables you to interpret a shift in lactate curves, the right way. It also helps to break free from outdated knowledge like determining the lactate threshold based on 4 mmol/l blood lactate. Contrary to a standard lactate analyses, INSCYD gives you way more actionable and scientific metrics, like :

For coaches and labs

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✅ Test remotely  ✅ No Special Equipment  ✅ Full Insights from a Single Test  ✅ Right fit for each sport

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✅ Right fit for each sport

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Athletes why train with generic plans when you can have a program tailored to your unique physiology? INSCYD is the key to unlocking your full potential. Find your dedicated INSCYD coach or lab here. 

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Keep reading to learn how to put these lactate test derived metrics into practice with revolutionary training zones.

But first we need to address a common mistake in analysing lactate data: ignoring body composition.

Body composition and LACTATE DILUTION SPACE

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, body composition and gender into account.

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Step 5: putting lactate test data into practice

The benefits of a lactate test are inherently tied to the actionable insights it provides.

Here are 3 examples of how you can put lactate test data into practice:

Create metabolic training zones

Stop using old fashioned %FTP training zones, instead create training zones based on the lactate (metabolic) profile.

For instance, base your endurance training on the FatMax intensity, your VO2max interval training on %VO2max and your zone 2 training on lactate concentrations. Learn more about the INSCYD Training Zone Builder.

Analyse the strength and weakness of athlete

A strength and weakness profile gives you a 360 view on athletic performance, at a glance. It visualises data against a peer comparison group and shows areas that need improvement.

INSCYD’s strength and weakness profile, showing key performance metrics derived for lactate performance test.

Combine this strength and weakness profile with a performance tracking chart over time, to monitor progress.

The INSCYD performance development chart
INSCYD’s Performance Tracking chart to monitor progress over time.

Top it off with a look into the future with performance projections. The INSCYD Performance Projections enable you to see exactly how much FTP (or any other parameter) changes when VO2max (or any other parameter) increases by say 5%.

By doing so, you know the effect of a training program, before you even start training.

Know how changes in your metabolic profile will contribute to performance improvements.

Create a nutrition plan

Use the fat and carbohydrate charts to see exactly how much energy you burn at any given exercise intensity.

INSCYD’s Fat and Carbohydrate combustion graph, derived from a lactate performance test.

You can add this data to your training zones and adapt your nutrition plan accordingly. You can also use it to determine your (marathon) pacing.

INSCYD Training Zones
INSCYD Training Zones allow you to show the additional physiological conditions that you want. For instance: total energy (kcal/h), fat (g/h) and carbohydrates (g/h) burned in a FatMax training zone.

Check out more actionable examples like creating interval training based on a lactate test or how Alpecin-Deceuninck Cycling Team uses lactate test data to prepare for key races via our content overview.

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 INSCYD will 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.

For coaches and labs

Watch Inscyd in action

With INSCYD, you can tailor training programs with unparalleled precision, ensuring your athletes achieve their peak performance faster and more efficiently.

Don’t let your athletes settle for anything less than their absolute best. Book a Free Demo with INSCYD today and experience firsthand how you can elevate your coaching game.



Athletes why train with generic plans when you can have a program tailored to your unique physiology? INSCYD is the key to unlocking your full potential. Find your dedicated INSCYD coach or lab here. 

Already have a coach? Experience INSCYD in action with your coach and redefine your training approach.

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