How to Calculate Electrolyte Balance
What is 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.
Step-by-Step Guide
- 1Sweat electrolyte content (approximate per litre): Na 920mg · K 200mg · Mg 36mg · Cl 1,400mg
- 2Electrolyte loss = Sweat rate (L/hr) × Duration (hr) × Concentration
- 3Sodium replacement is most critical for events > 2 hours
Worked Examples
Input
Sweat rate 1.5 L/hr · 3-hour event
Result
Sodium lost: 4,140mg · Potassium: 900mg
Far exceeds typical sports drink replacement
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