Muscle Cramps

How can muscle cramps be prevented? (Part 2)

How much should I drink? Hydration guidelines should be individualized for each person. The goal is to prevent excessive weight loss (>2% of body weight). You should weigh yourself before and after exercise to see how much fluid you lose through sweat. One liter of water weighs 2.25 pounds. Depending on the amount of exercise, temperature and humidity, body weight, and other factors, you can lose anywhere from approximately .4 to 1.8 liters per hour.

Pre-exercise hydration (if needed):

  1. 0.5 liters per hour for a 180-pound person several hours (three to four hours) prior to exercise.
  2. Consuming beverages with sodium and/or small amounts of salted snacks or sodium-containing foods at meals will help to stimulate thirst and retain the consumed fluids.

During exercise:

  1. Suggested starting points for marathon runners are 0.4 to 0.8 liters per hour, but again, this should be individualized based on body weight loss.
  2. There should be no more than 10% carbohydrate in the beverage, and 7% has generally been considered close to optimal. Carbohydrate consumption is generally recommended only after one hour of exertion.
  3. Electrolyte repletion (sodium and potassium) can help sustain electrolyte balance during exercise. Particularly when
    • there is inadequate access to meals or meals are not eaten,
    • physical activity exceeds four hours in duration,
    • during the initial days of hot weather.

Under these conditions, adding modest amounts of salt (0.3 g/L to 0.7 g/L) can offset salt loss in sweat and minimize medical events associated with electrolyte imbalances (for example, muscle cramps, hyponatremia).

Post-exercise:

  1. Drink approximately 0.5 liters of water for every pound of body weight lost.
  2. Consuming beverages and snacks with sodium will help expedite rapid and complete recovery by stimulating thirst and fluid retention.
Reviewed on 2/4/2014

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