Why does physical training change the sodium concentration of sweat?

Heat adaptation: Training, especially in hot conditions, results in thermal acclimatization. Sweat glands become more effective at cooling the body, increasing sweat production for better heat dissipation.

Sodium Saving: Intensive training promotes renal adaptation and sodium reabsorption. The kidneys adjust their function to conserve sodium, reducing its loss through sweat.

Changes in the sweat glands: With training, the sweat glands become more efficient. They secrete a more diluted sweat, containing less sodium, in order to conserve this crucial electrolyte for other bodily functions.

How does training modify the sodium concentration of sweat?

Increased sodium reabsorption:

The sweat glands have specific channels that reabsorb sodium before sweat reaches the skin's surface. Regular training stimulates this reabsorption, decreasing the sodium concentration in sweat.

Heat acclimation: With repeated exposure to heat, the body increases sweat production while reducing its sodium concentration. This happens because the sweat glands become more sensitive to aldosterone, a hormone that promotes sodium reabsorption.

Hormonal adjustments: Training changes hormone levels, including aldosterone and ADH (antidiuretic hormone), which play a key role in sodium regulation. Increasing aldosterone improves the ability of sweat glands to reabsorb sodium.

Practical Example:

An athlete who begins training regularly may initially lose a lot of sodium through sweat. However, after several weeks of training, the athlete's body adapts. The sweat glands become more efficient at reabsorbing sodium, resulting in sweat that is less concentrated in sodium. This conserves sodium for other vital functions, such as regulating blood pressure and maintaining fluid balance.

In summary, exercise training changes the sodium concentration in sweat through physiological and hormonal adaptations. , aimed at optimizing the effectiveness of thermoregulation while conserving essential electrolytes.


We have seen that the more an athlete is trained, the more quickly he will sweat. His body learns over time to regulate the heat produced during exercise.

The blue curve (trained athlete) shows that the athlete starts sweating after 18 minutes of effort while on the orange curve, (the sedentary man) needs an additional 7 minutes or 25 minutes to start sweating.
The two peaks at the start of each curve correspond to the sweat trigger for each athlete. The body initially releases sweat and sodium without really adjusting. Once the body analyzes the intensity of the effort provided, the sweat produced and therefore the sodium it contains finds its cruising speed. That is to say a plateau for an effort of continuous intensity (without variation in this).

The more an athlete is trained, the less sodium they will release. In the same way, your body learns to regulate the sodium it releases during exercise, it adapts. In this graph, the trained athlete will reach a plateau of approximately 22 mmol (sodium concentration) quickly when the sedentary man will reach a much higher plateau of 80 mmol.

That said, we can determine the level of an athlete based on several data:
- when he starts to sweat (sweat trigger)
- the level of sodium in your sweat (concentration in mmol)

From the sweat flow, we determine the losses of water and sodium and estimate the associated losses of other minerals.

  • Triathlete

    Curve of a triathlete on a bike for a 1 hour session at 150W.

    Sweat trigger after 2 min, just after making his first transition by putting on his armband out of the water. (The objective for 2025 is to make the armband waterproof for the practice of sorting in its entirety, particularly with the swimming part). After 6 minutes, the athlete reaches his plateau of around 17 mmol. Time for him to come down from a transition made quickly and not without stress. Here he is an athlete capable of completing an L-size triathlon in just under 5 hours.

  • Split run

    Curve of a runner on split.

    Sweat trigger after 20 minutes of warming up.

    The waves correspond to changes in intensity. Analyze and compare your sodium concentration thresholds in your sweat over time to surpass yourself. Like the aerobic and anaerobic thresholds, discover and push your limits thanks to the performance curve. This is an athlete capable of completing a half-marathon in less than 1h28. To discover your curve in the application, scroll to the right.