The most common myth surrounding fluid balance is: "Lots of water helps a lot." Sounds logical, but it is incomplete – and can even be harmful. High-performing individuals need not just water, but the right mix of fluids and electrolytes tailored to intensity, climate, and recovery windows. Studies show that those who strategically replenish electrolytes after exertion retain more fluid and recover faster than with water alone ^{[1] [2]}.

Hydration is more than just quenching thirst. Water distributes itself in intracellular spacesfluid within cells and extracellular spacesfluid outside the cells, e.g., blood plasma. Electrolytes such as sodiumthe most important mineral for regulating fluid balance, potassiumcrucial for cell function and nerve conduction, and chloridebalances electrical charges control where water remains in the body. When we sweat, we lose not only water but also electrolytes – especially sodium. Rehydration works optimally when both fluids and electrolytes are replaced together. Meanwhile, balance is crucial: too little leads to dehydration with performance decline; too much plain water can "dilute" sodium and trigger hyponatremialow sodium level in the blood – a clinically relevant risk with neurological symptoms ^[3].

For high performers, hydration mistakes are costly: even mild dehydration increases cardiovascular strain, shifts blood volume, and raises lactate levels, accelerating fatigue. In hot climates, isotonic beverages stabilize hematological markers better than water or no fluid at all – a sign of more efficient maintenance of water-electrolyte homeostasis ^[4]. After intense exertion, a carbohydrate-electrolyte drink improves fluid retention compared to water, both in summer and winter – an advantage for a quick return to full performance ^[1]. In contrast, those who only drink large amounts of water risk sodium dilution, with symptoms ranging from headaches to confusion; severe cases require emergency medical treatment ^[3].

In a crossover study involving young men, pure water was compared with a carbohydrate-electrolyte drink after strenuous exertion – each in amounts that compensated for sweat loss. Result: The drink solution led to higher fluid retention over 180 minutes in both summer and winter compared to water. In summer, blood glucose and serum sodium reacted more quickly, and subjective recovery (thirst, dryness) normalized faster – practically relevant when the next session follows shortly ^[1]. Another study had participants train in the heat and then drink either water or a 50 mmol/L sodium chloride solution at 150% of body weight loss – in addition to a meal. Despite food that contains sodium, the saline solution retained significantly more fluid in the body, while water led to a higher urine volume. Interpretation: Sodium is key to "binding" fluid and making rehydration sustainable ^[2]. Additionally, a thermoregulation chamber experiment over 120 minutes of exertion at 31 °C showed that isotonic drinks maintain blood volume and hematological markers more stable than water or no fluid – particularly relevant for performance and thermoregulation in the heat ^[4].

- Directly after intense exertion: Use a carbohydrate-electrolyte drink instead of just water to retain fluids longer and replace electrolytes. Aim: to rehydrate strategically within 60–180 minutes ^{[1] [2]}.
- Dose sodium intelligently: After heavy sweating (salt crusts on skin/clothing, hot climate), prefer drinks with ~50 mmol/L sodium or combine salty snacks with fluids. This reduces urine volume and increases retention ^[2].
- Personalized hydration plan:
- Before the session: Drink 5–7 ml/kg 2–3 hours prior; in heat, additionally small portions of electrolytes.
- During the session: In the heat, take small sips of isotonic fluid every 15–20 minutes; aim to compensate for 120–150% of expected sweat loss over the entire session or rehydration window ^[4].
- After the session: Consume 100–150% of body weight loss as drinks within 60–180 minutes; prioritize electrolytes during short recovery breaks ^{[1] [2]}.
- Consider the climate: In summer, the body dehydrates faster; electrolyte drinks improve subjective well-being and accelerate the normalization of hydration markers – useful during dense training blocks ^[1].
- Safety first: No "overdrinking." Avoid excessive water intake without electrolytes, especially during long endurance sessions. Watch for symptoms like nausea, headaches, confusion; in cases of severe signs, seek medical evaluation immediately – hyponatremia is a medical emergency ^[3].
- Monitoring: Weigh before/after sessions (nude weight). A 1 kg weight loss roughly corresponds to 1 liter of fluid. Clear, light yellow urine color and stable body weight indicate adequate hydration ^[4].

Hydration is a performance lever – it's not just the quantity that matters, but the right mix of water and electrolytes at the right time. Start today: Weigh yourself before/after your next session and compensate for 100–150% of the loss with an electrolyte drink; adjust the strategy according to heat and recovery windows.