Essentials of Nutrition for Sports

If you cannot keep up with losses, pace: Reduce exercise
intensity to a level that allows yo

u to replace what you are losing.

Recent Studies

Weight loss during exercise is directly related to fluid losses

during exercise.

Predicting fluid loss before exercising based on initial body

weight, exercise type, exercise intensity, ambient temperature, and percent relative humidity accounted for only about half of the variability of observed loss in recreational exercisers.

Cycling in a hot environment for an hour? Drinking 1,000

milliliters of cool water immediately before cycling or splitting the fluids into four 250 milliliter doses at 0, 15, 30, and 45 minutes during the hour results in no significant thermoregulatory or performance differences.

Electrolyte Additives

What is lost with sweating and hard breathing (the lungs

moisturize air) is mostly plain water. Some electrolytes or salts (sodium, potassium, chloride, etc.) are lost, but it is mostly water. Water is the most important item to replace.

Expensive athletic drinks or solutions are not necessary for usual

athletic activity.

Electrolytes may help the body absorb and retain water. Aerobic endurance athletes who exercise daily for more than a

couple of hours can deplete the body’s reserves of some electrolytes, principally sodium and chloride.

Sodium and chloride may come from salty snacks, supplements,

or be present in fluids consumed.

For a more complete discussion, read

Sweat Mineral Losses

on

page

21

.

Hyponatremia

Rehydrating without adequate sodium can result in low blood

sodium or hyponatremia, potentially life-threatening. Read more about sodium and hyponatremia on pages

24

and

166

.

Calorie Additives

Calories in solution help water and electrolytes move from the

gut into the bloodstream.

For exercise more than 1 hour in duration, studies have shown

that solutions containing carbohydrate allow for improved performance compared with plain water.

A few studies have shown that calories can help performance

even during shorter events.

Sports drinks, soft drinks, and fruit juices provide the calories as

well as replace some of the modest

electrolyte losses that occur with

sweating. Note that fruit juices must usually be diluted to be tolerated while exercising, and that even so, some individuals do not tolerate fruit sugar (fructose) as well as other sugars.

Even if you are only going to exercise a short time, it makes

sense to always have some calories in what you drink. They may not be necessary for performance today, but who knows—maybe you will end up exercising longer than you were planning, or perhaps it will help you keep your glycogen topped up and allow you to perform better tomorrow. Those who train daily or exercise more than 10 hours per week are always fighting glycogen depletion.

Read more about carbohydrate solutions under

Maltodextrin

Nutrition

on page

51

and

Nutrition While Exercising

on page

15

.

Sports Drinks

Sports drinks can be helpful.

Before- and during-exercise sports

drinks generally do not contain protein or fat. These ingredients are sometimes included in recovery drinks.

Nutrition for Sports, Essentials of 31