What are electrolytes?
Electrolytes are minerals that carry an electrical charge when dissolved in fluid. The primary electrolytes relevant to exercise are sodium, potassium, magnesium, and calcium. They regulate fluid balance between cells, enable nerve impulse transmission, and drive muscle contraction and relaxation.
How they work
Sodium is the primary electrolyte in extracellular fluid and drives fluid retention and absorption. Potassium regulates intracellular fluid and works with sodium in the sodium-potassium pump that enables nerve signalling. Magnesium is a cofactor in ATP production and muscle relaxation. Calcium triggers muscle contraction by binding to troponin in muscle fibres.
What the research says
- Sweat contains 500–1500mg of sodium per litre — the primary electrolyte lost during exercise
- Electrolyte supplementation during exercise lasting 60+ minutes improves endurance performance and reduces cramping risk
- Hyponatraemia (low sodium) from drinking plain water without electrolyte replacement is a documented risk in endurance events
- Post-exercise electrolyte replacement accelerates rehydration compared to water alone
Effective dose
Needs vary significantly by individual sweat rate and training duration. As a general guide: 500–1000mg sodium, 200–400mg potassium, and 100–200mg magnesium per hour of intense exercise in heat. For sessions under 60 minutes at moderate intensity, water alone is typically sufficient for most people.
What to check on the label
Sodium content is the most important figure on an electrolyte product. Many electrolyte supplements are underdosed on sodium — marketing-focused products often lead with potassium or magnesium which sound more impressive but are less critical to replace acutely. Check sodium per serve first.
Safety
Safe within recommended ranges. Excessive sodium intake over time is associated with elevated blood pressure in salt-sensitive individuals. Athletes with high sweat rates have significantly higher sodium needs than sedentary individuals — standard dietary sodium guidelines may not apply.