HEALTH AND FITNESS: The science of sports drinks
What do you drink during exercise? For most people, the answer is probably water. But many athletes and people who do vigorous exercise are likely to consume a sports drink like Gatorade or Powerade while they work out. While there are some differences among the various sports drinks, these beverages are specially formulated to meet the demands of athletes engaged in prolonged, intense exercise. In fact, most contain a similar combination of water, sugar, and salt, along with flavoring to make them palatable. Research and practical experience support the use of sports drinks to improve performance in endurance events (think running and cycling) that last an hour or more. Let’s explore the rationale behind the components of sports drinks.
Obviously, water is important for replacing sweat loss during exercise, something that is even more critical in a hot, humid environment. During intense exercise on a hot day, sweat losses can be well above one liter per hour. Failure to replenish this water loss can lead to poor performance due to physiological and psychological fatigue. In extreme cases, severe dehydration can lead to hyperthermia and heat stroke. For most athletes, 500–1000 ml (16–32 oz.) of fluid per hour is sufficient, but more may be needed to meet individual needs.
Carbohydrate replacement has long been associated with endurance performance. Vigorous exercise requires lots of carbohydrates in the form of glucose to fuel the active muscles. Your muscles can use 60–120 g of glucose per hour, depending on intensity. You store glucose in your liver and muscles as glycogen which gets broken down during exercise. But these supplies are limited and are diminished after an hour or so of intense exercise. Recommended intake is in the range of 30–60 g carbohydrate per hour during exercise to deliver glucose to the muscle sustain exercise. Almost any carbohydrate will work, but sports drinks contain sugars that are absorbed quickly. It is also essential to maintain blood glucose since, as I tell my students, “if your blood glucose drops, you drop!”
Sports drinks also contain some salt. First the salt replaces what you lose in your sweat, preventing a dangerous condition called hyponatremia. Fortunately, most people eat enough salt throughout the day and don’t lose enough in their sweat to create problems. Another reason for including salt is that glucose is absorbed with sodium, so having both gets the carbohydrates into your blood faster. Additionally, levels of sodium in the blood act to stimulate thirst. Consuming salt makes athletes thirsty, and thirsty athletes are more likely to drink more.
The composition of sports drinks is important, but the way they are consumed matters, too. Research shows that drinking smaller amounts of fluid more frequently, 12 ounces every 15 minutes, is better than 32 ounces at the end of an hour. Carbohydrate content is important, but more isn’t necessarily better. Most sports drinks are in the range of 8 percent, which is ideal for getting the sugar absorbed into the blood. Drink temperature matters, too, and colder drinks are absorbed faster. Obviously, you are more likely to drink beverages that taste good, so finding a flavor you like is important.
Now that you know what is in most sports drinks and why, you may wonder if you need one during exercise. Unless you are doing intense exercise lasting over an hour, probably not. Water is sufficient for most people who exercise. And consider this: sports drinks contain as much sugar and calories as soda. If you are exercising to lose weight, a sports drink during (or after) exercise might sabotage your efforts.