Essentials of Nutrition for Sports

Hydration

Hydration Key Points •^

Adequate hydration is crucial

to athletic performance.

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Keep fluids handy.

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Begin training or events hydrated.

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The longer the event, the more important it is to keep up with fluid losses.

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For single-day events: o^

Aim to drink 16 ounces (2 cups, 500 milliliters, 1 standard waterbottle) per hour while exercising moderately or in temperate conditions.

o^

Aim to drink up to 32 ounces (1 quart, 1 liter) per hour when exercising at high intensity or in the heat.

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For multiple-day events: o^

Replace fluids lost, up to 48 ounces (1.5 quarts, 1.5 liters) per hour when exercising in the heat.

o^

Reduce exercise intensity to a level that allows you to replace what you are losing.

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Chilled and flavored fluids im

prove palatability and promote

hydration.

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Carbohydrate concentration to a maximum of 6% (240 calories per quart or liter) may improve th

e rate of rehydration as well as

improve performance by providing energy and sparing glycogen.

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Sodium to a maximum concentration of 1,000 milligrams per quart (liter) may improve the rate of rehydration as well as prevent hyponatremia.

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There is no evidence that other minerals in hydration products improve performance.

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There is no evidence that proprietary substances in sports drinks confer any advantages over readily available nutrients.

Requirements: Adequate Intake (AI)

The 2004 US Food and Nutrition Board (FNB) adult daily total

water intake AI is 3.7 liters (qua

rts) for men and 2.7 liters for

women.

This includes all water contained in food, beverages, and

drinking water.

Aerobic endurance athletes need more.

Why Hydrate?

Dehydration worsens athletic performance. Replacing liquids that are lost through exercise is one of the

easiest and important aids to performance in endurance sports.

Fluids are intracellular—within cells, and extracellular—for

example in blood vessels.

Fluids allow the body’s cells to function optimally. Maintaining

good hydration is essential to mainta

ining strength while exercising.

Blood is about 50% fluids. Reduction of blood volume from

dehydration affects performance quickly.

Dehydration may reduce not only current performance but also

subsequent training effectiveness. It

is associated with a decrease in

metabolic rate and a shift to carbohydrate energy use at rest—resulting in less carbohydrate available for high-intensity exercise.

A conscious effort to drink may be required—most athletes do

not voluntarily drink enough.

It is easy to get dehydrated. Ov

er-hydration is unusual, but

occurs—most often in those who

exercise at low or moderate

intensity for many hours and overdrink, especially with salt-poor solutions.

What Percent Dehydration Affects Performance?

Some studies have shown that as

little 2% dehydra

tion (3-pound

weight loss for a 150-pound athlete) affects performance.

Nutrition for Sports, Essentials of 27