Why Hydration Is So Important for Fitness

For digestion, circulation, regulation of body temperature, cushioning of organs, and the health of your joints, skin, and immune system, water is indispensable. Day after day, hydration fights fatigue and improves physical and mental performance.

Conversely, even mild dehydration can lead to impaired cognition and reduced energy. Dehydration can also lead to an increase in blood pressure, as your heart tries to pump blood that is thicker than normal; during exercise, you might experience a racing heart and ­decreased performance.

To offset these side effects, ingest half an ounce per pound of body weight per day, adding ­another 16 to 24 ounces per hour of sweating, advises Kriegler. For a 150-pound person, that amounts to a baseline of about 75 ounces per day.

But, experts say, remain flexible about that amount. “That number should increase or decrease depend­ing on your activity level, body size, and rate of sweating, as well as the temperature and humidity,” notes Poli.

“If you’re waiting until your workout
to start hydrating, you’re too late.”

Alcohol, caffeine, sugar, artificial sweeteners, medications, exposure to pollutants, and stress also affect hydration levels, he adds, so your hydration needs may change significantly from day to day.

Overhydration is possible, but it’s far less common than underhydration, says Poli. “Many people don’t feel the urge to drink until after they are mildly dehydrated. Their thirst threshold is set too high.”

This delay has a big impact on athletes. “If you’re waiting until your workout to start hydrating, you’re too late,” Ogden says.

With this fact in mind, shift your focus from drinking as much water as possible to drinking it consistently. “You don’t need to tote a gallon jug with you 24-7,” says Poli, “but you probably need to make an effort to take a drink more often.” (For a guide to getting the hydration you need, visit “Everything You Need to Know About Hydration.”)