Sodium is the electrolyte lost in the highest concentration in sweat (typically 20-80 mmol/L depending on sweat rate and acclimatisation). During exercise lasting more than 60-90 minutes, sodium replacement alongside fluid prevents hyponatraemia (dangerously low blood sodium) — caused by excessive plain water intake that dilutes sodium. Athletes sweating heavily should consume 500-1000mg of sodium per hour in warm conditions. Sports drinks, electrolyte tablets and salt capsules are common sodium sources. Sodium also stimulates thirst and fluid retention, improving rehydration effectiveness.
Key points
- Primary electrolyte lost in sweat
- 500-1000mg/hr in hot conditions
- Prevents hyponatraemia from excess plain water
- Stimulates thirst and improves rehydration