Sodium for endurance: how much is needed per hour?
We talk a lot about carbohydrates, less about sodium. Yet, during long-duration exercise, it is the mineral you lose in the greatest quantity, and the only electrolyte that is truly useful to replace during exertion. Here are some concrete guidelines.
What sodium does during exercise
- It helps your body retain the water you drink rather than eliminating it.
- It maintains blood volume, thus your ability to cool yourself and fuel your muscles.
- It maintains thirst, which helps you drink enough.
- It participates in the absorption of glucose in the intestine.
Why there isn't one single number
The amount of sodium lost varies enormously from one person to another. Sweat concentration ranges from approximately 200 mg to over 1,500 mg of sodium per liter, and sweat rate ranges from less than 0.5 liters to more than 2 liters per hour depending on heat, intensity, and your body size. Two runners side by side can therefore lose very different amounts.
Practical guidelines
| Situation | Sodium per hour |
|---|---|
| Effort of less than 90 minutes, cool weather | Not necessary |
| Long effort, cool weather or light sweat | 300 to 500 mg |
| Long effort, hot weather or heavy sweat | 500 to 800 mg |
| Very salty sweat, heat and effort of several hours | 800 to 1,000 mg, sometimes more |
These are starting points, to be adjusted according to how you feel during training.
Are you a heavy salt loser?
- You have white streaks on your cap or clothing after a workout.
- Your sweat stings your eyes or tastes very salty.
- You crave salty foods after long workouts.
- You often feel dizzy or drained after long exercise in hot weather, even if you have been drinking.
If you check several boxes, aim for the high end of the ranges. A lab sweat test provides a precise figure if you want to go further.
The trap: too much water, not enough sodium
Drinking large quantities of pure water over several hours can dilute the sodium in your blood. This is exercise-associated hyponatremia, which mainly affects participants who drink well beyond their thirst during long events. Symptoms include nausea, headaches, swollen hands, and confusion. In severe cases, it is a medical emergency.
Two simple rules: drink according to your thirst rather than a forced schedule, and put sodium in what you drink.
And cramps?
The link between sodium and cramps is less solid than people think. Exercise-associated cramps seem mainly linked to muscle fatigue and an intensity higher than that of training. Sodium can help some people, but it does not replace preparation adapted to the event.
How to apply this with your drink
One serving of ELIXYR Endurance Fuel contains 340 mg of sodium and 30 g of carbohydrates.
- One serving per hour: 340 mg, sufficient in cool weather.
- Two servings per hour: 680 mg and 60 g of carbohydrates, adapted to most long efforts.
- Heavy salt loser in hot weather: add a salt capsule or a salty snack to supplement.
For the rest of the formula, see our article Why 500 mg of electrolytes in an endurance formula.
To remember
If you have a heart or kidney condition, hypertension, or are on a low-salt diet, talk to your doctor before increasing your sodium intake.