Why Hydration Is More Complex Than It Appears
Dehydration impairs performance. But so does overhydration (hyponatremia) — a condition that has hospitalized athletes who drank too much plain water during endurance events.
What Sweat Actually Contains
Sweat is not just water. It contains sodium (dominant), chloride, potassium, magnesium, and calcium. When athletes replace sweat losses with plain water only, they dilute blood sodium concentrations. For sessions or competitions lasting more than 60 minutes in warm conditions, plain water is not optimal.
Sweat Rate: Individual Variation Is Large
Average sweat rate ranges from 0.5 to 2.5 litres per hour — a fivefold difference. Test it: weigh an athlete nude before and after a 60-minute session without drinking. Difference in kg = approximate sweat loss in litres.
Hydration Timing Protocol
| Timing | Recommendation |
|---|---|
| 2 hours before | 400–600ml water or electrolyte drink |
| During (under 60 min) | 400–800ml/hr, plain water or dilute sports drink |
| During (60+ min) | 500–1000ml/hr of sports drink with sodium |
| Post-exercise | 1.2–1.5L per kg of bodyweight lost |
Recognizing Dehydration
Mild (1–2%): Thirst, darker urine, minor performance decrease.
Moderate (2–4%): Significant performance impairment, fatigue, headache, amber urine.
Severe (4%+): Nausea, muscle cramps, dizziness — requires medical attention.
The Urine Check
Pale straw = well hydrated. Clear = possibly overhydrated. Dark yellow/amber = dehydrated. Make urine checks a normal part of athlete education. Ten seconds of information that guides action.