Electrolyte Balance

Electrolytes (sodium, potassium, magnesium, chloride) are lost in sweat and must be replaced during prolonged exercise. Sodium loss (~920mg/L) is most critical — replacing water without sodium can cause dangerous hyponatraemia.

1. 1Sweat electrolyte content (approximate per litre): Na 920mg · K 200mg · Mg 36mg · Cl 1,400mg
2. 2Electrolyte loss = Sweat rate (L/hr) × Duration (hr) × Concentration
3. 3Sodium replacement is most critical for events > 2 hours