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Healthy hydration for physical activity

Dehydration is recognized as having a detrimental effect during exercise. Indeed, dehydration has been shown to increase heart rate and body temperature:3 the heart has to work faster when plasma volume is reduced to maintain delivery of oxygen and nutrients to the muscles.

Numerous studies, reviewed in the American College of Sports Medicine (ACSM) position stand,2 show that dehydration increases physiologic strain and perceived effort to perform the same exercise task, and that warm-hot weather increases this phenomenon. The ACSM also considers that dehydration above 2% of the body mass can degrade aerobic exercise performance, and therefore endurance performance.2

It is therefore recommended to drink before, during and after the exercise, in volume sufficient to match the water losses, without waiting for thirst to appear.2 For exercise lasting less than one hour, water is sufficient to cover the body’s needs.1

A recent study performed in children by Kavouras et al,4 confirmed these results, by demonstrating that improving hydration status (by education and facilitated access to water) can enhance performance in young athletes exercising in warm conditions.

The American Academy of Pediatrics reminds parents and caregivers that “Water is generally the appropriate first choice for hydration before, during, and after most exercise regimens”.5

References
  1. Péronnet F. Healthy Hydration for Physical Activity. Nutrition Today 2010;45:S41-4.
  2. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39:377-90.
  3. Armstrong LE, Maresh CM, Gabaree CV, Hoffman JR, Kavouras SA, Kenefick RW, Castellani JW, Ahlquist LE. Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake. J ApplPhysiol 1997;82:2028–35.
  4. Kavouras SA, Arnaoutis G, Makrillos M, Garagouni C, Nikolaou E, Chira O, Ellinikaki E, Sidossis LS. Educational intervention on water intake improves hydration status and enhances exercise performance in athletic youth. Scand J Med Sci Sports 2011.; doi: 10.1111/j.1600-0838.2011.01296.x
  5. Committee on Nutrition and the Council on Sports Medicine and Fitness. Sports drinks and energy drinks for children and adolescents: are they appropriate? Pediatrics2011;127:1182-9.

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