Also known as: Sodium, Chloride, Electrolyte tablets, Rehydration salts, Hydration multiplier
EnduranceStrong evidence
Minerals lost in sweat, replaced to maintain fluid balance during prolonged exercise. Sodium is the one that matters most, and individual sweat losses vary far more than any product label acknowledges.
Typical dose
300.0–1500.0 mg per day
During prolonged sessions and in heat; drink to thirst
What it is
Electrolytes are minerals carrying an electrical charge when dissolved. In a sports context that means sodium, chloride, potassium, magnesium and calcium, though sodium and chloride dominate what is actually lost in sweat.
Sweat sodium concentration varies enormously between individuals, from roughly 200 to over 2,000 mg per litre. Someone at the high end loses ten times the sodium of someone at the low end at the same sweat rate, which is why generic recommendations are of limited use.
The salty sweater is a real phenomenon rather than a marketing invention. If you finish sessions with white residue on your skin or kit, you are losing sodium at the high end and need considerably more than a standard tablet provides.
How it works
Sodium is the principal mineral in the fluid outside cells and is what determines how much fluid the body holds. Replacing it during prolonged sweating maintains blood volume and helps retain the fluid you drink rather than simply passing it.
Sodium also drives glucose absorption in the intestine through a shared transporter, which is why rehydration solutions contain both. The carbohydrate is not only fuel; it improves fluid uptake.
Drinking large volumes of plain water during prolonged exercise dilutes blood sodium. In extreme cases this becomes genuinely dangerous, and it is the reason drinking to thirst rather than to a schedule is the standard advice.
What the evidence shows
Sodium replacement during prolonged exercise in the heat is well established as improving fluid retention and maintaining blood volume.
For sessions under about an hour in temperate conditions, evidence of benefit is weak. Most people do not need an electrolyte drink for an hour in the gym, whatever the marketing suggests, and water is adequate.
The link between electrolytes and cramp is weaker than commonly assumed. Cramp appears more closely tied to neuromuscular fatigue than to mineral loss, though sodium may play a role in some individuals. Anyone buying electrolytes purely to stop cramping should know the evidence is not strong.
Dosing
For sessions over 90 minutes, or shorter ones in heat, 300 to 1,500 mg of sodium per hour covers most people. Heavy and salty sweaters need the upper end or beyond.
Many commercial tablets supply only 200 to 400 mg of sodium, which is at the low end of useful. Check the sodium figure rather than the count of minerals on the label — a product listing eight electrolytes at trivial doses is worse than one supplying adequate sodium alone.
Work out your own losses rather than following a generic figure. Weigh yourself before and after a long session to estimate sweat rate, and note whether you leave salt marks on your kit. Drink to thirst rather than to a schedule.
During prolonged sessions and in heat; drink to thirst
Competition status
Permitted — not on the WADA Prohibited List
Category
Endurance
Safety and side effects
Electrolyte products are safe for healthy people during exercise. Excess sodium simply gets excreted, and the main complaint is nausea from drinks mixed too concentrated.
The genuine risk during endurance events is the opposite of what most people expect: drinking too much plain water and diluting blood sodium. This is dangerous and has caused deaths in mass-participation events. Drinking to thirst rather than forcing fluid on a schedule is the protection.
Anyone whose blood pressure or kidney function is being managed should speak to their doctor before using high-sodium products regularly, and potassium-containing products deserve the same check.
Who should avoid it
Speak to your doctor before regular use of high-sodium or potassium-containing products if your blood pressure or kidney function is being managed. Do not force fluid on a schedule during long events — drinking excessive plain water can dangerously dilute blood sodium. Mix to the stated concentration; stronger is not better.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
