Electrolytes for runners: what they do and what they do not solve

Sodium, potassium, magnesium, and calcium are the four electrolytes that govern fluid balance, nerve signalling, and muscle contraction during endurance exercise. Losing them through sweat is inevitable. Sodium loss varies significantly between individuals, and this matters because hyponatremia (low blood sodium) can affect endurance athletes in events lasting over four hours.

This guide covers what electrolytes actually do during a run, how to estimate your needs, what the science says about supplementation, and why electrolyte replacement is necessary but not sufficient for sustained performance. It sits within the broader endurance nutrition framework.

Electrolytes are minerals that carry electrical charge in solution. During exercise, they serve three primary functions: sodium and chloride maintain blood plasma volume, which determines how effectively your cardiovascular system delivers oxygen to working muscles. Potassium and sodium create the electrical gradients across cell membranes that trigger muscle contraction. Calcium initiates the actin-myosin binding that produces muscular force, while magnesium governs muscle relaxation and is a required cofactor for ATP synthesis.

When you sweat, you lose all four. But sodium dominates sweat composition, accounting for roughly 90% of electrolyte losses. This is why most electrolyte products focus on sodium, and why sodium replacement is the primary concern during long efforts.

How much sodium do runners lose per hour?

The answer depends on three variables: sweat rate (how much you sweat), sweat sodium concentration (how salty your sweat is), and environmental conditions (heat and humidity increase both).

A sweat test (offered by companies like Precision Fuel and Hydration, or a sports medicine clinic) provides personalised data. Without one, a reasonable starting point for most runners in temperate conditions is 500 to 700 mg of sodium per hour during efforts over 90 minutes.

Do electrolyte tablets and drinks actually improve performance?

The evidence is mixed. Some reviews found no consistent evidence that electrolyte supplementation improves endurance performance in well-hydrated athletes exercising in moderate conditions. However, in hot conditions or during ultra-distance events, sodium supplementation may reduce the incidence of muscle cramps and lower hyponatremia risk.

The practical takeaway: electrolyte replacement prevents performance degradation rather than enhancing performance. It keeps the floor from dropping out, rather than raising the ceiling.

What do electrolytes not solve?

Three performance factors that electrolyte products cannot address:

1. Energy production. Electrolytes maintain fluid balance and nerve function, but they do not provide fuel. Carbohydrate (from gels, drinks, or food) remains the primary performance fuel for efforts over 60 minutes.

2. Micronutrient gaps beyond sodium. Most electrolyte tablets contain sodium and potassium with minimal magnesium or calcium. Yet magnesium is the electrolyte most directly linked to cellular energy production. A runner who replaces sodium religiously but neglects daily magnesium intake is addressing hydration while ignoring the ATP synthesis pathway.

3. Mitochondrial efficiency. Like energy gels, electrolyte products operate at the fuelling layer. The cellular layer, where mitochondria convert fuel into usable energy, requires different support: daily polyphenolic compounds that protect mitochondrial membranes from oxidative damage.

How does OLEUS complement electrolyte and fuelling strategies?

Electrolytes maintain hydration. Gels provide carbohydrate. OLEUS supports the cellular machinery that converts both into performance.

The OLEUS Daily Shot includes magnesium (the electrolyte most electrolyte tablets underserve), alongside oleuropein, vitamins B6, C, and D. The Pre-Activity Shot, taken 60 minutes before racing, targets mitochondrial activation before the effort begins.

The three layers stack: electrolytes for hydration, carbohydrate for fuel, and OLEUS for the cellular engine. None replaces the others.

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Sources

1. Nielsen, F.H., Lukaski, H.C. (2006). Update on the relationship between magnesium and exercise. Magnesium Research, 19(3), 180-189. PubMed: 17172008

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