Post-workout exhaustion may be due to inadequate hydration caused by a significant loss of sodium in sweat, which water alone cannot compensate for.

noli's read

This advice is based on sound physiological principles regarding electrolyte balance. It is scientifically established that sodium is the primary electrolyte lost in sweat, and that replacing it with water alone can lead to dilutional hyponatremia in certain individuals, a phenomenon documented in observational studies and sports medicine journals (e.g., Journal of the International Society of Sports Nutrition). Individual variability in sodium loss is also recognized, confirming that requirements are not universal. However, the statement may be perceived as slightly exaggerated in suggesting that sodium is the major cause of post-workout exhaustion; fatigue after an intense session is often multifactorial, also involving the depletion of glycogen stores and central nervous fatigue. Although the need for sodium is real for endurance athletes or those exercising in the heat, the average amateur athlete does not always require specific supplementation beyond a balanced diet. The link between hydration and performance is supported, but the impact of sodium should be nuanced according to the duration and actual intensity of the exercise.

the sources

1. 1Maughan RJ et al. 2016
2. 2Hew-Butler T et al. 2015