A critical finding from current sports medicine guidance challenges a widespread athletic practice: drinking water alone during prolonged exercise carries significant physiological risk. Athletes exercising for more than 90 minutes require up to 1,000 mL fluid combined with 500–1,000 mg sodium per hour to maintain blood sodium concentration and prevent performance impairment.
Diluting blood sodium through water-only hydration—a condition known as hyponatraemia—can impair cognitive function, increase fatigue, and compromise athletic safety. The new evidence-based protocol underscores that sodium intake is not optional for endurance activities exceeding 90 minutes; it is a medical necessity.
The recommendation applies across varying environmental conditions and exercise intensities. Athletes are urged to personalise their hydration strategy based on individually measured sweat rate, established during training sessions rather than on competition day.
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