Proper Hydration for Athletes

Female rugby players drink water and cool off at side of pitch

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Proper hydration is helpful for achieving the best performance in elite athletes. Adequate fluid intake is also helpful for recreational exercisers to exercise at their best. There have been recommendations about how much water or sports drinks are needed and over the years athletes were advised to drink much more water than we now know is necessary.

Guidelines on nutrient recommendations are published by the Institute of Medicine of the National Academies. They state that the vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide. They don't provide specifics, such as the number of glasses of water per day, because fluid needs can be met through a variety of sources besides drinking water alone. The group makes special recommendations for athletes in the area of water, sodium, and potassium.

The International Society of Sports Nutrition updated recommendations in 2018 regarding hydration for athletes. They recommend hydrating throughout the day, including before, during, and after exercise.

They recommend drinking a sports drink when exercising 30 minutes or more. They also state that during a marathon, it's best if runners listen to their bodies and drink when they feel they need to.

Watch for Dehydration and Hyponatremia

Hyponatremia, or water intoxication, was the result of this "drink, drink, drink" mantra, and now recommendations are going the other way, "Drink Less." For many exercisers, water intoxication is a very real and very serious complication from drinking too much water. The numbers of triathlon and marathon participants who develop symptoms of water intoxication continue to grow as more and more novice exercisers have entered these events.

So what is the right amount of fluid to drink? Well, that all depends, and in fact, it may not be that important to try to figure it out.

The longer and more intensely you exercise, the more important it is to replace lost fluids.

For an elite athlete, a loss of 2% of body weight in fluid has been linked to a drop in blood volume. This drop makes the heart work harder in order to move blood through the bloodstream.

For elite athletes,​ this decrease can result in a slight decrease in performance.

Dehydration in athletes may also lead to fatigue, poor performance, decreased coordination and muscle cramping. The International Society of Sports Nutrition provides guidelines for athletes regarding proper hydration and fluid replacement.

Hydration Guidelines

If you feel that you need some sort of guideline to determine how much you should be drinking, use the following as a starting point.

Drink 500ml (about 2.5 cups) of water or sports drink before bedtime, another 2.5 cups of water upon waking, and then 400-600ml (1.5–2.5 cups) of water 20-30 minutes before your workout. During exercise, drink 12–16 fluid ounces (1.5–2 cups) of water or sports drink every 5-15 minutes. In longer workouts, potassium, magnesium, and 300–600 mg of sodium per hour are recommended. After your workout, drink 3 cups of water for every pound loss. You can also weigh yourself before and after you exercise to get a sense of how much fluid you typically lose.

Sports Drinks

Sports drinks can be helpful to athletes who are exercising at a high intensity for 60-90 minutes or more. It's necessary to replace losses of the electrolytes sodium, potassium and magnesium during exercise.

Keep in mind that under normal situations most exercisers are unlikely to deplete these minerals during regular training.

If, however, you find yourself exercising in extreme conditions or for long times (an Ironman or ultramarathon) consider adding a sports drink with electrolytes.

Hyponatremia (low blood sodium concentration) may occur during longer events when athletes drink excessive amounts of plain water.

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Article Sources
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  1. Kerksick, C.M., Wilborn, C.D., Roberts, M.D. et al. ISSN exercise & sports nutrition review update: research & recommendationsJ Int Soc Sports Nutr 15, 38 (2018).

Additional Reading
  • Lewis G. Maharam, MD.FACSM (chair),Tamara Hew DPM, Arthur Siegel MD, Marv Adner, MD, Bruce Adams, MD and Pedro Pujol, MD, FACSM. "IMMDA Revised Fluid Recommendations for Runners and Walkers." IMMDA. 6 May 2006.