Water is a major component of the human body, accounting for approximately 73% of lean body mass. Hypohydration (the loss of water greater than the ingestion) has many negative effects on athletic performance. It can result in increased body temperature and consequently elevated heart rate. It can also increase perceived exertion and cause an athlete to feel more fatigued than usual. Mental function declines and can impact motor function, ability to make decisions, and concentration. Gastric emptying is also slowed which can result in stomach cramping. Electrolyte losses can occur during exercise, which can result in muscle cramping and fatigue. Fluid loss of 1% body weight results in elevated core body temperature.

At 3% of body weight it results in impaired performance. At 5% of body weight it results in cardiovascular strain. At 7% of body weight it results in decreased ability to regulate heat. At 10% of body weight it can result in heat stroke. Signs and symptoms of dehydration include dark, strong smelling urine, decreased urination frequency, rapid resting heart rate, muscle soreness and cramping, thirst, headache,

■ FLUID NEEDS BEFORE EXERCISE

The American College of Sports Medicine (ACSM) recommends that athletes ingest approximately 16 ounces of fluid two hours before exercise to ensure adequate hydration and to al-low for proper time to excrete excess fluid. On warm days, athletes may need to drink an additional 8 to 16 ounces of fluid 30 to 60 minutes be-fore exercise. Well-hydrated athletes will void light colored urine within 60 minutes of exercise.

■ FLUID NEEDS DURING EXERCISE

Fluid losses during exercise are dependent on many factors including the intensity of exercise, duration of exercise, temperature and humidity of the environment, type and amount of clothing worn, level of fitness and acclimation, size of the athlete, and genetic predisposition to sweating. The ACSM recommends that enough fluids be consumed during exercise to replace all fluids lost through sweating. They also recommend that fluids be cool and flavored to enhance palatability and increase voluntary fluid intake, contain carbohydrate to enhance performance, and contain sodium chloride to promote rehydration. It is more beneficial to space fluid intake along regular intervals, rather than drink a lot of fluid all at once. For example, 8 ounces every 15-20 minutes.

■ FLUID NEEDS AFTER EXERCISE

Athletes should ingest at least 20 ounces of fluid for every pound of weight lost during exercise. Rapid and complete hydration can only be complete when both water and sodium chloride are ingested, and sports drinks are usually a good source of both. Water, juices, and milk can also be sources of post-workout fluids. For exercise of duration greater than 60 minutes, sports drinks are the preferred choice.