By Roberta H. Anding, M.S., Baylor College of Medicine and Texas Children’s Hospital

Edited by Kate Findley, The Great Courses Daily

If you participate in competitive sports or want to get the most out of your workout, staying hydrated while exercising is crucial. Professor Anding explains what fluids are best to optimize your workout.

Fluids and Exercise

How much fluid do you need when you exercise? In order to measure how your fitness regimen is affecting your hydration levels, you must get on the scale before and after your workout. 

Keep in mind that a scale can only tell you how much you weigh. It cannot measure your body fat percentage or how much lean muscle mass you have. However, it can tell you whether or not you’re hydrated. 

“For example, I could go out and run a mile in Houston, and when I come in, I’ve lost four pounds,” Professor Anding said. “There is no way I’ve lost four pounds of body fat—the energy equation won’t allow it. That’s the bad news.”

Fluids lost through sweat account for the four pound deficit. While you may still rejoice that you lost weight, a one to two percent decrease in your body weight is going to affect your performance.

For example, if you’re a marathoner, even if you lose as little as one to two percent of your body weight during physical activity, that is enough to decrease your performance by 15 to 20 percent. Thus, for athletes and people who compete in any way, shape, or form and want to boost their performance, Professor Anding recommends water hydration as a legal, sports-enhancing aid. 

We often overlook the simple things and instead search for complex ways to improve our performance. The marketplace is flooded with expensive equipment and supplements, and the media has no shortage of stories on athletes who resort to illegal measures to try and get a performance edge. They’ve skipped over the value of hydration. 

Is Water Adequate?

The American College of Sports Medicine (ACSM) provides guidelines on what to drink while exercising. If you exercise for less than an hour, at moderate intensity, then water is fine. The rules change if your activity is intense or you are exercising in the heat for an hour or more. 

“I have modified the ACSM guidelines for my environmental conditions in Houston,” Professor Anding said. “I’ll say if you’re outside exercising in the heat for more than 30 minutes, you probably need to switch to a sports drink.”

Sports drinks such as gatorade are intended to replenish fluids lost during physical activity. They are not a lunchtime beverage. Often, sports drinks are high in sugar and calories and thus should not be consumed unless you are burning them off through exercise.

First, sports drinks provide fluid. When a beverage is flavored, we tend to drink more of it than when it’s unflavored. 

Additionally, they provide the electrolytes—particularly sodium—that are lost in sweat. If you’re outside exercising and you’re sweating, your sweat tastes salty. 

Bananas and Athletes

Sodium is the major electrolyte that’s lost in sweat, but if you ask the average consumer what you need to eat or drink more of when you’re outside exercising, they would say potassium. However, the potassium losses in your sweat are really insignificant.

Many athletes, even at the professional level, eat bananas while performing. The bananas are intended to provide some fluids but predominantly potassium. 

When you’re sweating intensely, you can develop cramps, and your hands and the arches of your feet may seize up. Athletes eat bananas, then, with the expectation that the potassium will alleviate the cramping.

However, what’s actually causing the cramping is the loss of sodium, not potassium, in your sweat. Thus, although bananas are a great source of nutrition, they are not an effective solution to cramping.

The next time you’re engaging in intense exercise, Professor Anding recommends bringing a sports drink, as it provides a source of calories and fluids and replaces the sodium lost through sweat.

This article was edited by Kate Findley, Writer for The Great Courses Daily.

Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.