Hydration During Swim Training: Complete Guide
Swimer Team
International swimming coaches and high-performance technicians with 40+ years of combined experience.
Quick summary: Yes, you dehydrate swimming even though you're surrounded by water. A swimmer loses 0.5-1 liter of sweat per hour. Protocol: drink 400-600ml 2 hours before, 150-250ml every 15-20 minutes during training, and 500-750ml after. For sessions over 60 minutes, add electrolytes.
Hydration in swimming is one of the most underestimated aspects of training. Since you're in water, you don't perceive sweat — but your body loses fluids at the same rate as any land sport. A 2% body weight dehydration reduces performance 10-20%.
Why do you dehydrate in water?
- You sweat, but don't notice: Pool water washes away sweat immediately. Studies show swimmers lose 0.5-1 liter per hour.
- Water temperature: Pools at 26-28°C cause active thermoregulation, increasing sweat production.
- Breathing: Intense breathing during swimming expels water vapor.
Hydration protocol for swimmers
| When | Amount | What to drink |
|---|---|---|
| 2 hours before | 400-600 ml | Water |
| 30 min before | 200-300 ml | Water or isotonic drink |
| During (every 15-20 min) | 150-250 ml | Water (<60 min) or isotonic (>60 min) |
| After | 500-750 ml | Water with electrolytes or recovery drink |
Dehydration signs
| Level | Signs | Performance impact |
|---|---|---|
| Mild (1-2%) | Thirst, dry mouth, dark urine | -5 to -10% |
| Moderate (2-4%) | Headache, premature fatigue, cramps | -10 to -20% |
| Severe (4%+) | Dizziness, confusion, nausea | Health risk — stop immediately |
Electrolytes or just water?
- Sessions under 60 minutes: Water is sufficient if well hydrated beforehand.
- Sessions 60-90 minutes: Water with a pinch of salt or light isotonic drink.
- Sessions over 90 minutes or doubles: Isotonic drink with sodium, potassium, and carbs (30-60g/h).
Common hydration mistakes
- "I don't sweat, I don't need to drink": You do sweat — the pool water hides it.
- Drinking only after: Post-workout rehydration doesn't compensate for during-session loss.
- Drinking too much at once: 1 liter at once causes stomach discomfort. Drink little and often.
- Only water in long sessions: Without sodium, water dilutes electrolytes (hyponatremia risk).
Combine good hydration with adequate pre-workout nutrition and a dryland warmup. Hydration is especially important in endurance sessions. Create your free Swimer account to train with method.
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Step by step
- 1
Hydrate 2 hours before
Drink 400-600ml of water two hours before the session. This ensures you arrive well hydrated without stomach discomfort.
- 2
Bring a bottle to poolside
Drink 150-250ml every 15-20 minutes during training. Don't wait until thirsty — thirst appears at 1-2% dehydration.
- 3
Add electrolytes in long sessions
For sessions over 60 minutes, add sodium and potassium. You can use a sports drink or make your own: 500ml water + salt + honey + lemon.
- 4
Rehydrate after training
Drink 500-750ml with electrolytes within 30 minutes post-session to replenish lost fluids.
Frequently asked questions
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