The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


Should You Drink Water or Sports Drinks During Physical Activity?

Thursday, Jul 25, 2019

The human body is approximately 60% water by weight. Water is the nutrient that is most often neglected by those who are highly physically active.

Research has shown time and time again that as little as a 2% loss of body weight through sweating can have a significant effect on athletic performance. This is equivalent to a 180-pound person losing about 3.5 pounds of water. In the hot summer weather, you can lose over four pounds of sweat per hour during heavy physical activity.

Dehydration can not only impair physical performance but can also lead to very serious health consequences such as heat stroke. When we sweat, we lose water and electrolytes (mostly sodium and potassium) as our body tries to keep cool. If you don’t drink enough fluids during physical activity, especially in the heat, then dehydration can quickly sneak up on you.

So, is it better to drink plain water or a sports drink during physical activity? The answer is that it really depends on the situation. 


Most sports drinks contain three basic ingredients; water, simple sugar and electrolytes. Don’t confuse these with energy drinks, which typically contain moderate to high amounts of caffeine and may or may not contain sugar.

The sugar content is just as important as electrolytes because depletion of the body’s carbohydrate stores can have a detrimental effect on performance. Carbohydrates are a very important fuel source for all cells, including muscles. That’s why there is sugar in a sports drink - to help replace carbohydrates that are being used by the working muscles and to help prevent blood sugar levels from falling.

Hundreds of published studies over the last half-century have examined the effects of sports drinks versus water on athletic performance. The overwhelming consensus from these studies is that sports drinks provide a significant advantage over water during moderate to vigorous activities lasting longer than an hour or so, especially in hot weather.

For someone riding 50 miles on a bicycle on a hot day, a sports drink is the better choice to replace electrolytes and carbohydrates. For someone walking the dog for 15 minutes on a hot day, plain water is all that’s needed.


The calories in a sports drink also make a difference. If you are overweight and/or sedentary, you may not need those extra calories or the added sugar.

Sports drinks are a lot like running shoes. Did you know that a large percentage of running shoes sold in the U.S. never go for a run? Similarly, a big percentage of the sports drinks sold in the U.S. are consumed by people who are sedentary or just minimally physically active. Many people assume that sports drinks must be a healthy choice because they see athletes drinking them. That doesn’t make it a good choice for the person who is sitting on their couch watching a game.


Current guidelines for fluid replacement during exercise from the American College of Sports Medicine are as follows: Consume 6-12 ounces of fluid during every 15-20 minutes of exercise, more during hot weather.    

  • Half or full marathon 
  • Triathlon or duathlon
  • Long training run or bike ride
  • Long practice for sports
  • Game time for any active sport (football, soccer, hockey, basketball, tennis, etc.)
  • Hiking or brisk walking for longer than an hour
  • Manual labor (roofing, construction, lawn work, etc.)