Electrolyte Balance and Sports Drinks: Which One, When and Why?
Isotonic, hypertonic, hypotonic — there are shelves full of options. Which ones support performance, and which are just sugary water? A scientific comparison.
Why Do Electrolytes Matter?
During sport, sweat carries away not just water but also sodium, potassium, chloride, magnesium and calcium. These minerals govern muscle contraction, nerve transmission and fluid balance. Drinking only water can lead to rehydration without electrolytes (a risk of hyponatremia).
Key Electrolytes and Their Roles
| Electrolyte | Main Role | Loss Through Sweat |
|---|---|---|
| Sodium | Fluid balance, muscle contraction | High |
| Potassium | Intracellular fluid, heart rhythm | Moderate |
| Magnesium | Muscle relaxation, enzymes | Low–moderate |
| Calcium | Muscle contraction, bones | Low |
Types of Drink
Isotonic (6–8% carbohydrate + electrolytes)
When: Moderate-to-intense exercise lasting more than 60–90 minutes
Examples: Gatorade, Powerade, homemade
Homemade recipe:
- 500 ml water
- 2 tablespoons sugar (24 g)
- 1/4 teaspoon salt
- Lemon juice (for flavor)
→ ~6% carbohydrate, ~500 mg sodium
Hypotonic (<4% carbohydrate)
When: Short sessions, for fast rehydration
Examples: Electrolyte tablet solution, diluted sports drink
Advantage: Fast gastric emptying
Hypertonic (>8% carbohydrate)
When: Energy boost — not during exercise, but before or after it
Caution: May increase the risk of dehydration
Commercial Sports Drinks Compared
| Product | Carbohydrate | Sodium | Notes |
|---|---|---|---|
| Isotonic (standard) | 6–7% | 400–500 mg/L | Balanced |
| Energy drink | 11–13% | Low | Not suitable |
| Coconut water | 6% | Low (~250 mg) | Not enough sodium |
| Electrolyte tablet + water | 0–1% | 500–1,000 mg | Electrolytes only |
Long Distances and the Risk of Hyponatremia
In long races such as marathons or triathlons, drinking only water can dilute blood sodium. This condition is called hyponatremia and can lead to serious neurological symptoms. During long events, choose 150–200 ml of a sodium-containing drink every 20 minutes.
Rule of Thumb
- <60 min: Water is enough
- 60–90 min: An isotonic sports drink or water with added electrolytes
- 90+ min: A carbohydrate + electrolyte drink is a must
This article is general information. Talk to a paediatrician or dietitian before deciding on a nutrition plan or supplements for your child.