Body composition in performance testing: stop ignoring it

When expressing VO2max in oxygen uptake per kg bodyweight, or FTP in watts per kg bodyweight, you immediately understand the importance of body composition. However, it seems like not all coaches and labs feel the same when expressing blood lactate values in mmol per liter. Do you know which liters we talk about? And if so, do you take this into account when performance lactate testing?

When you take a lactate sample and the analyzer shows: 4 mmol/l, do you know which “liter” it is talking about? Is it liters body content? Liters of blood?

Here’s what it is, and as a results, why body composition matters in all performance testing. Not only when looking at VO2max or critical power or FTP or..

Body composition in lactate testing

In lactate testing, the mmol per liter is showing you a concentration of lactate. As always when looking at a concentration, both the solute and the solvent are important.

One teaspoon of sugar (solute) in your cappuccino (solvent) will lead to a different sugar concentration then the same teaspoon of sugar in your espresso.

Body composition, solute solvent
One teaspoon of sugar (solute) in your cappuccino (solvent) will lead to a different sugar concentration then the same teaspoon of sugar in your espresso.

Imagine your smallest athlete riding a stationary bike at 200 watts. The leg muscles produce lactate – and you measure the lactate concentration with a blood lactate analyzer: 4 mmol/l.

Now imagine we could put the exact same leg muscles into another – in this case larger athlete. We then ask the athlete to ride at the exact same intensity. Results? You’ll see a blood lactate concentration below 4 mmol/l. Simply because the athlete is larger and the lactate will dilute in a larger space.

In other words: the exact same muscles produce the exact same amount of lactate, but you will measure a (totally) different blood lactate concentration.

This is not only the case when comparing lactate concentrations between individuals with a different body composition, but also when comparing lactate results within an individual who is changing body composition (e.g. losing weight, increasing muscle mass etc.)!

Conclusion: if you’re working with lactate measurements and you want to compare results over time (within an individual) or between individuals, you need to know more about body composition. Specifically, you want to know more about the lactate dilution space.

Before we talk about what body composition characteristics determine lactate dilution space and how to measure them, let’s first look at another example.

Body composition difference between male and female

It goes without saying that the body composition of men and women are different. To give one example: on average, women have a higher body fat percentage than men. This decreases lactate dilution space, since lactate does not dilute in fat.

Knowing this, you should think about the use of conventional lactate profile concepts such as D-Max, 4 mmol/l etc. in female athletes. All those concepts have been developed and validated only in males.

INSCYD is probably the only software for performance analysis out there which takes gender into account. We hope this is the trigger for female cyclists around the world to start questioning their current methods of performance analysis. We’re happy to say this was one of the reasons why professional women’s cycling team CANYON//SRAM partnered with INSCYD.

INSCYD Coach about: Body composition

Tenille Hoogland INSCYD coach
Tenille Hoogland

Tenille Hoogland is the founder and Head Coach of Elements Sports Coaching. She is committed to empowering female athletes to fulfill their athletic goals and play to their best. She does this through one to one and group coaching (Project 51).

“As a professional triathlete, power to weight ratio was drilled into my head.  I wanted to be lighter so I trained harder. I ate less. I got injured. With INSCYD, coaches can do so much better to support the health of their athletes and ultimately their performance. We can train with our unique physiology.

Understanding body composition and lactate concentration is an important part of exercise prescription not only because we can better identify the intensity of training intervals but because we can identify how long (or short!) it will take the athlete to recover. This means more quality work that gets you to your goals  –  body composition change, personal bests or just having more fun on epic adventures.

INSCYD has changed the game for athletes and coaches. If you want to save time and effort to play to your best it only makes sense to train with your body. Take out guess work. You are not the same as everyone else.”

What determines lactate dilution space

To make all this information actionable, we need to know what determines lactate dilution space and how to measure it.

Since lactate is water-soluble, it can dilute/exist in parts of the body that contain water (like the blood where it often gets measured).

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

The next question is: how to measure body water content and convert it into lactate dilution space.

How to measure lactate dilution space

Now we know lactate exists in parts of the body that contain water, we want to understand something about the amount of water in an individual body.

Although there are measurement tools that measure body water content, it’s often easier to measure or estimate body fat. Some athletes may even have a body fat scale at home. To go from body fat to a fairly accurate estimation of body water is easy, although you need to take gender into account.

Download our whitepaper and get 3 steps to actually calculate your (athlete’s) lactate dilution space.

INSCYD uses different default values for lactate distribution space for males and female.

Additional body composition information

The INSCYD software will share more body composition information in the report. To name a few:

  • Available glycogen – depending on your sport
  • Active muscle mass – depending on your sport
  • Body Mass Index (BMI)
Body composition and compartment

Take action

We challenge you to better understand what happens inside the body of your athlete. Reconsider conventional lactate profile concepts like 4 mmol/l, that do not take gender or body composition into account.

Start with checking out the white paper, that enables you to track progress within an individual who is changing body composition and compare performance tests between individuals with different body compositions.