The premise: Sports drinks have been getting a lot of bad press lately, due to their high amounts of sugar. But some studies have found that carbohydrate-containing beverages do actually increase endurance exercise performance, compared to water and placebo drinks. "Previous studies have demonstrated further improvements with the help of supplements that contain both carbohydrates and protein—compared to carbohydrate only," says researcher Lisa Ferguson-Stegall.
But what happens if the level of carbs is reduced? Along with her team, Ferguson-Stegall hypothesized that a low-carbohydrate beverage with extra protein would continue to extend time to exhaustion.
The set-up: To test their theory, the experts monitored 15 trained endurance cyclists while they performed two long rides: A three-hour ride and an intense ride that pushed the cyclists to 85 percent of their aerobic capacity (VO2 max) until they reached exhaustion. On one ride, the athletes were given a standard carbohydrate supplement. On the other ride, they received a low-carbohydrate supplement with 1.2 percent added protein. The beverages were given out in 275-ml doses every 20 minutes.
The results: The average time to exhaustion was 26 minutes with the standard supplement and 31 minutes with the low-carb plus protein supplement. The biggest difference was found among the athletes exercising at or below their ventilatory threshold (VT), the point at which breathing starts to become increasingly difficult. For the eight cyclists in this group, average time to exhaustion was 45 minutes with the low-carb plus protein beverage, while the group drinking the standard beverage lasted only 35 minutes.
The researchers concluded that a lower carbohydrate-containing drink with a moderate amount of protein leads to improved endurance performance in trained long-distance cyclists. The low-carb drink increases performance despite containing 50 percent less total carbohydrate and 30 percent fewer calories relative to a higher carbohydrate beverage.
Which drink should you choose?
"There are a lot of products out there," says Ferguson-Stegall. "Some have a really high calorie content, and may actually provide more calories than are needed to adequately recover from many workouts." Meaning, you don't necessarily have to drink back all the calories you lost. Though she wouldn't recommend one specific drink, Ferguson-Stegall points out: "It's important to know that you can extend endurance effectively with a supplement that contains fewer calories and carbohydrates, and has the added benefits of protein, which is important for mediating muscle damage and tissue repair as well as the post-exercise adaptation to the exercise stimulus."