Electrolyte Loss per Hour of Exercise Calculator

Sodium loss varies dramatically: 500-2,000mg per hour depending on sweat rate (0.5-2.0L/hour) and sweat sodium concentration (400-2,000mg/L). Heavy sweaters in hot conditions can lose 2,000-3,000mg per hour — equivalent to one teaspoon of salt. For comparison, a typical sports drink contains only 200-300mg sodium per 12oz serving. During exercise over 90 minutes, you need 500-1,000mg sodium per hour to maintain electrolyte balance. Salt tablets (500-1,000mg each) or electrolyte powders are more effective than sports drinks alone for high sodium loss.

Early signs: Muscle cramps (especially calves, hamstrings), headache, nausea, dizziness, dark urine. Advanced signs: Confusion, vomiting, severe muscle weakness, irregular heartbeat, seizures. The most dangerous condition is hyponatremia (low blood sodium) from drinking too much plain water without electrolytes — symptoms mimic dehydration but require opposite treatment. Prevention: Weigh before and after exercise. Every kg (2.2lb) lost = ~1L fluid deficit needing replacement with ~700mg sodium. Never drink more than 1L/hour of plain water. Use electrolyte drinks for sessions over 60 minutes.

High heat (30°C+/86°F+) and humidity (>70%) increase sweat rate by 50-200%. At 20°C, a runner sweats ~1L/hour. At 35°C with 80% humidity, the same runner sweats 1.5-2.5L/hour. This doubles or triples electrolyte loss. Acclimatization (7-14 days in heat) reduces sweat sodium concentration by 30-50% as your body conserves salt. Heavy sweaters (>1.5L/hour) in hot conditions need special attention: 1,000-1,500mg sodium per hour, plus 200-300mg potassium and 50-100mg magnesium. Monitor urine color — pale yellow is ideal, dark amber signals dehydration.

For sessions under 60 minutes: plain water is sufficient. For 60-120 minutes: sports drink with 200-500mg sodium per 12oz, drink to thirst. For 2-4 hours: electrolyte powder in water (500-1,000mg sodium/L), plus solid food with salt. For 4+ hours (ultra-endurance): 750-1,000mg sodium per hour via electrolyte capsules or salty food, plus 200-300mg potassium and 80-100mg magnesium per hour. Never rely on thirst alone — set a timer and drink 150-250mL every 15-20 minutes. Pre-load with 500mg sodium 60 minutes before exercise in hot conditions.