Drinking Extra Water Won't Cool You Down and Can Be Dangerous

By Christopher DiPasquale

It’s late summer. Fall sports practices are starting up, and it is brutally hot outside.

You are sweating through your gear. You start chugging water. You might even grab a few sports drinks. You think all this liquid is acting like an internal air conditioner to bring your core temperature down.

It doesn't.

While replacing lost fluids allows your body to keep sweating, drinking extra water or sports drinks beyond what you need won't lower your body temperature. Worse, drinking too much fluid too fast can actually be deadly.

The Danger: "Water Intoxication"

When you flood your system with extra fluids, you dilute the salt in your blood. This causes a dangerous condition called hyponatremia (low blood salt), or water intoxication.

When blood sodium drops too low, water rushes into your cells, causing them to swell like water balloons. When this happens in brain cells, it causes confusion, seizures, and can even be fatal.

The Sports Drink Myth: Many people think sports drinks protect against this because they contain electrolytes. But the salt concentration in sports drinks is far lower than what's in your blood. Drinking massive amounts of sports drinks can still cause hyponatremia.

Where Did "Drink Ahead of Thirst" Come From?

For thousands of years, humans worked and ran in the heat while drinking only when thirsty. So why were we taught to drink on a fixed clock?

Starting in the 1980s, sports drink companies funded exercise research that framed any weight loss from sweat as dangerous. Advertising campaigns convinced coaches and athletes that human thirst was an unreliable signal and that you had to drink before feeling thirsty. Modern sports medicine has since debunked this: your natural thirst is an extraordinarily accurate signal.

How Your Body Actually Cools Down

Water replacement doesn't cool you—your body's natural systems do:

• Sweat Evaporation: Your body pushes blood to your skin and secretes sweat. As that sweat evaporates into the air, it pulls heat off your body.

  
  

• Brain Protection: When you get too hot, your brain makes you feel exhausted. This is a protective safety switch designed to force you to slow down so your muscles stop generating heat.

  
  

• Heat Acclimatization: It takes about 10 to 14 days of activity in the heat for your body to adjust. Over two weeks, your body naturally adds blood volume and increases its sweat rate so you stay safe.

  
  

Action Steps for Fall Preseason

1. Drink to Thirst: For most athletes, listening to your body's thirst cues is the safest way to hydrate without risking hyponatremia.

   
   

2. Ease Into Practices: Give student-athletes 2 full weeks to gradually build up practice intensity and equipment in late-summer heat.

   
   

3. Watch the Humidity: On high-humidity days, sweat cannot evaporate into the air. When sweat doesn't evaporate, you don't cool down—no matter how much water you drink.

   
   

4. Check Field Heat Stress (WBGT): Instead of standard weather apps, coaches can use affordable handheld Wet Bulb Globe Temperature (WBGT) meters (available online starting around $80 to $150). These measure direct sunlight, humidity, and wind right on the practice field to tell you when it's time to take breaks or modify practice.

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Christopher DiPasquale, PT, DPT, PhD, OCS, SCS, COMT, CHT is a physical therapist at Performance Physical Therapy & Sports Medicine, with offices in Hebron and Colchester, Connecticut. He is board certified by the American Board of Physical Therapy Specialties in Orthopedic Physical Therapy and Sports Physical Therapy, a Certified Hand Therapist by the Hand Therapy Certification Committee, and is a Certified Orthopedic Manual Therapist. Visit pptsm.com for more information.