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by Susan Nordmark, Dietetic Intern, UIC, 2000

 Now that the weather is heating upits time to reach for that water bottle.  Taking in fluid during exercise is one of the most important techniques a person can perform to maintain or improve their performance.  Unfortunately, its importance is often overlooked.  The body regulates its temperature by sweating.  Common sense tells us that as we sweat, we need to replace the lost body fluid.  Research has shown however, that most people replace only 50% of the fluid they lose during exercise.  Increased perspiration without replacing lost fluid leads to dehydration.  This leads to decreased blood volume, where the heart compensates by working harder.  Dehydration may start out as lightheadedness, progress to irritability and fatigue (heat exhaustion) and eventually lead to a dangerously high core body temperature (heat stroke).  If you wait until you are thirsty to drink, you are already dehydrated!

Hydration guidelines:

WHO:                Anyone who exercises.

WHAT:              Drink what you like (you will take more in that way).  Water is always a good suggestion for workouts less than one hour.  Consider a sports drink if you plan on exercising for more than one hour to provide more benefit.  Stay away from caffeinated products, as they require even more fluid intake.  Avoid fruit juices (such as orange or grapefruit) before and during exercise, as they decrease water absorption.

WHEN:              Drink adequate fluids (8 cups) one full day in advance of exercise.  Drink two cups (16 oz.) two hours before exercise (allowing time for elimination).  Drink at regular intervals during exercise.

WHY:                 To prevent heat related illnesses.  Maintain ability to exercise at optimum levels.

HOW:                Practice drinking during easy exercise.  Use a bottle belt.  Stash water bottles along your route before you exercise.

HOW MUCH:   For each pound lost during exercise, replace with one pint (16 oz.) of fluid.  (This means you have to weigh yourself before and after workouts.)  Most people lose 2-6 cups of sweat per hour of exercise.

TIPS to avoid dehydration during events:


      Dress lightly in hot/humid weather

      Drink at every opportunity

      Stay out of the sun

      Practice drinking before races

      Squeeze the top of the cup to avoid spilling while drinking

      Carry a straw to drink from the glass

      Water is more useful in your stomach than it is poured over your head



1999 - 2010 Transitions Nutrition Consulting

Northbrook IL, tel 888-794-0788.

If you have any comments or questions, email us at info@netRD.com. This page was last updated on January 09, 2010.

Original web design by Julie Wehmeyer, while she was a dietetic intern at UIC