Water makes up ~60% of body weight and is essential for:
| Function | How Hydration Helps |
|---|
| Temperature regulation | Sweat dissipates heat |
| Nutrient transport | Carries fuel to muscles |
| Waste removal | Clears metabolic byproducts |
| Blood volume | Maintains cardiovascular function |
| Joint lubrication | Protects joints |
| Fluid Loss | Effects |
|---|
| 1% body weight | Elevated heart rate, reduced performance |
| 2% body weight | Significant performance decline |
| 3-4% body weight | Serious impairment, heat illness risk |
| 5%+ body weight | Dangerous, medical emergency possible |
Example (70kg athlete):
- 2% loss = 1.4kg = 1.4 liters = ~15% performance drop
Read our complete guide: Cycling Hydration Guide.
| Condition | Fluid per Hour |
|---|
| Cool, low intensity | 400-500ml |
| Moderate conditions | 500-700ml |
| Hot or high intensity | 700-1,000ml |
| Very hot, intense | 1,000-1,200ml |
Sweat rates vary enormously:
| Sweater Type | Sweat Rate |
|---|
| Light sweater | 0.3-0.5L/hour |
| Average | 0.5-1.0L/hour |
| Heavy sweater | 1.0-1.5L/hour |
| Very heavy | 1.5-2.5L/hour |
Read: How Much Water Cycling Per Hour.
- Weigh yourself (nude) before exercise
- Exercise for 1 hour
- Track all fluid consumed
- Weigh yourself (nude) after
Formula:
Sweat rate = Pre-weight - Post-weight + Fluid consumed
Example:
- Before: 70.0kg
- After: 69.2kg
- Fluid consumed: 500ml (0.5kg)
- Sweat rate: 70.0 - 69.2 + 0.5 = 1.3L/hour
| Timing | Strategy |
|---|
| 2-4 hours before | 5-7ml/kg (350-500ml) |
| 30 min before | 200-300ml if needed |
| Duration | Strategy |
|---|
| < 60 min | Drink to thirst |
| 60-90 min | 400-600ml/hour |
| 90+ min | 500-1,000ml/hour + electrolytes |
| Goal | Strategy |
|---|
| Rehydration | 1.5× fluid lost |
| Timing | Over 2-4 hours |
| Include | Electrolytes with water |
| When to Use | Notes |
|---|
| Short efforts (< 60 min) | Usually sufficient |
| Cool conditions | Lower electrolyte loss |
| Between training | Regular hydration |
| When to Use | Notes |
|---|
| 60+ min exercise | Replace electrolytes |
| Hot conditions | Higher sodium needs |
| High-intensity | Need carbs too |
| When to Use | Notes |
|---|
| Hot weather, heavy sweaters | High electrolyte needs |
| Low-carb athletes | Electrolytes without calories |
| Between workouts | Recovery hydration |
| Distance | Strategy |
|---|
| 5K | Usually no need |
| 10K | Drink if available |
| Half marathon | Every aid station |
| Marathon | 150-200ml every 15-20 min |
Read: Hydration for Runners.
| Duration | Strategy |
|---|
| < 60 min | Bottle optional |
| 1-2 hours | 500-750ml |
| 2-4 hours | 500-1,000ml/hour |
| 4+ hours | Careful planning essential |
| Distance | Key Challenges |
|---|
| Sprint | Minimal |
| Olympic | Bike is key opportunity |
| Half Ironman | Steady intake throughout |
| Ironman | Critical—plan carefully |
| Sign | Indicator |
|---|
| Urine color | Light yellow (lemonade) |
| Frequency | Every 2-4 hours |
| No symptoms | Comfortable |
| Sign | Indicator |
|---|
| Urine color | Dark yellow (apple juice) |
| Frequency | Infrequent |
| Symptoms | Thirst, headache, fatigue |
| Sign | Indicator |
|---|
| Urine color | Clear (water) |
| Frequency | Very frequent |
| Risk | Hyponatremia possible |
Thirst indicates ~1% dehydration already.
Solution: Drink on a schedule during long efforts.
Excess water without electrolytes causes hyponatremia.
Solution: Don't force fluids; include sodium.
Long efforts require electrolyte replacement.
Solution: Use sports drinks or add salt.
GI issues from new drinks during racing.
Solution: Practice race hydration in training.
| Adjustment | Details |
|---|
| Increase volume | +50-100% more fluid |
| More electrolytes | Higher sodium losses |
| Pre-cool | Cold drinks, ice |
| Reduce intensity | Allow for conditions |
| Adjustment | Details |
|---|
| Still hydrate | Sweat less obvious but still occurs |
| Warm fluids | Easier to drink |
| Monitor | Easy to forget in cold |
| Adjustment | Details |
|---|
| Increase fluids | Dry air increases losses |
| Monitor urine | Stay on top of status |
| Electrolytes | Still important |
Monitor:
- Urine color (light yellow is good)
- Weight stability during exercise
- Performance and how you feel
- Absence of headaches and fatigue
For shorter efforts, yes. For longer efforts (90+ min), a schedule helps ensure adequate intake before thirst indicates dehydration.
Yes—hyponatremia (low blood sodium) from overdrinking is dangerous. Don't force fluids beyond thirst, and include electrolytes.
The mild diuretic effect is offset by the fluid in coffee/tea. Moderate caffeine consumption doesn't significantly impact hydration.
