In recent years, the sports nutrition industry has increasingly focused not just on what athletes should eat before a workout or competition, but afterward, while their body is regrouping and replenishing its fuel supply. Well, if you're an endurance athlete, you might want to listen up—because a recent study published in the Journal of Applied Physiology suggests the answer includes…caffeine.
The study was conducted by a team of Australian researchers who went seeking the perfect cocktail to persuade athlete's bodies to reabsorb glycogen after exercise. Glycogen fuels muscles during exertion—and it is seriously depleted during endurance training, which burns muscular fuel over an extended period of time. In order to return to a similar level of performance in short order, you need your body to restore glycogen to the muscles as quickly as possible. And, as researchers discovered, this is best achieved by following exercise with a mixture of carbohydrates and caffeine, more so than by either alone.
Any marathoner is familiar with the importance of carbohydrates before, during, and after a race—and caffeine is, of course, a familiar stimulant found in many endurance gels and energy bars. But the Australian researchers found a new effect—that following exercise with both carbs and caffeine appreciably increased athletes' rate of glycogen re-absorption. In fact, the group receiving a combination of carbs and caffeine had 66 percent more glycogen in their muscles four hours after exercise. As the study's lead author, Dr. John A. Hawley of the Royal Melbourne Institute of Technology University, said, "If you have 66 percent more fuel for the next day's training or competition, there is absolutely no question you will go farther or faster."
The study's method involved completely depleting athletes' muscles. The study's leaders asked the group of seven athletes to exercise on a machine until fatigued, then to eat a low-carb meal. The next day, the same athletes exercised to fatigue again, with no more food on board. After this (exhausting) process, they were given either a carbohydrate shake alone, or a carb and caffeine shake. Then—finally!—they got to rest, waiting through a four hour recovery followed by muscle biopsies and blood samples to measure their glycogen. Ten days later, the researchers repeated the entire experiment, but with the groups switched, so that the caffeine group got only carbs, and the carb group added caffeine. The results showed a 66 percent improvement in glycogen replenishment for the caffeine group.
Researchers still don't know exactly why this effect occurs, but believe that caffeine may aid in glucose absorption from blood to muscle. In essence, eating the carbohydrates produces glucose and insulin, which are circulating in the blood and which are the basis of glycogen—hence the importance of ingesting carbs after endurance exercise—but the caffeine helps these reach muscle, where the glucose is stored as glycogen. Caffeine's role may be partly to intensify the activity of enzymes that aid in glucose uptake.
The biggest problem for everyday athletes without a coach to consult, of course, is in knowing how much caffeine to consume. The researchers gave participants the equivalent of five to six cups of strong coffee—a lot of caffeine. You probably want to experiment with a little less, unless you are already a hardcore java addict.