Muscle soreness, burning muscles, cramps…

It is common to hear that this phenomenon results from the production of lactic acid, a poison that limits performance during exercise.

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Unfortunately, this is an error that has been perpetuated in the sporting world for many years…

1) The reality of lactic acid

Lactic acid cannot exist in our body or muscles.

Indeed, the body functions within a narrow pH range, and lactic acid has a pH that is far too acidic to be present in the blood.

It is a matter of terminology: lactic acid is confused with lactate.

2) Lactate

Previously, we thought that high lactate production was harmful to performance.

Recent studies have shown us the opposite, and its production is a real source of energy for our muscles, thanks to various physiological recycling and conversion mechanisms.

Explanations:

The body produces energy through glycolysis by breaking down glycogen (the body's sugar stores).

This glycolysis is closely linked to lactate production, which is its end product.

The more intense the effort, the more the glycolysis process is called upon to produce energy to activate muscle contraction, and the higher the concentration of lactate measured in the blood.

The destination of lactate:

A large part is converted and used as energy available to the body.

The other part is used to replenish glycogen stores (sugar reserves) in the liver.

3) Train to use lactate more effectively

We produce lactate at all exercise intensities, not only through the so-called anaerobic pathway (without oxygen).

But the more intense the effort, the higher the lactate production.

Through training, the body will develop physiological adaptations to better use the lactate system, producing more while optimizing its recycling at high intensities.

The best athletes are those with the highest blood lactate levels, unlike untrained athletes

An untrained athlete will be limited in their effort not by producing too much lactate, but rather because they do not produce enough and do not optimally benefit from the energy regeneration process.

This leads us to reconsider certain training methodologies, particularly when preparing for long-endurance efforts (ultra-trail, ultracycling, Ironman…).

In practice:

• Performing high- and very-high-intensity sessions
• Physical efforts involving high muscular demands

Polarization is therefore essential for progress, alternating intensive sessions needed to establish physiological adaptations to the lactate mechanism with low-intensity endurance efforts.

4) Pain and fatigue during exercise: who is responsible?

Timothy Noakes's central governor theory provides us with some answers.

Depending on multiple parameters (energy stores, hydration, body temperature…), the brain will send signals to the body to slow down an effort deemed too intense or unusual, thereby protecting the body from potential risks by establishing a safety margin.

Brain function is placed at the center of physical-effort regulation, with the aim of always maintaining vital balance through anticipation.

 »The sensation of fatigue would therefore be partly the result of an emotion, rather than a purely physical limitation«

With this perspective, training would allow us not only to develop our physiological abilities, but also to push our limits mentally in order to overcome thresholds of fatigue and pain.

CONCLUSION

Muscle fatigue during exercise results from many factors, and lactic acid is not the responsible enemy since it does not exist in the body.

We need to talk about lactate production: lactates are not waste products, but essential elements in energy creation, to be transformed and used by the body during and after exercise.

Through training, we can optimize the production and recycling of lactate in order to improve athletic performance.