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Editor’s Note: For more on what to eat following a hard workout, please read Monique Ryan’s new Recovery Nutrition Primer.
Almost any cyclist, pro or dedicated local racer is very familiar with the many performance benefits of caffeine. You may indulge in a caffeine laden early morning wake-up call for a pre-dawn training session, and now have a variety of sports bars, beans, gels, and other caffeinated aids available to offer up a training boost. With all the hundreds of studies on caffeine consumption before and during exercise and its positive performance effects, there has been no study on caffeine consumption after exercise- until now.
Published this past May in the Journal of Applied Physiology, a group of researchers in Australia studied the effects of co-ingestion of caffeine and carbohydrate after hard training on muscle glycogen stores (Journal of Applied Physiology, May 2008). The initial results were promising for caffeine fans. Let’s take a look.
“Endurance athletes often have to replenish muscle glycogen stores rapidly between training sessions, and consequently there has been a lot of research on recovery nutrition to see how we can boost muscle glycogen stores,” said researcher John Hawley of the RMIT University in Bundoora, Australia. Hawley proposed that since caffeine consumed during exercise and before exercise increase the availability of glucose, the same could be true when caffeine is consumed after exercise-induced glycogen depletion. In contrast, caffeine consumed at rest in untrained persons does not have the same effect.
Researchers decided to test their theory using highly training subjects. Cyclists and triathletes who were biking 12 to 15 hours per week completed a ride to exhaustion the night before the experimental trial. They consumed a low carbohydrate meal that evening, and again completed a short ride to exhaustion the next morning to ensure that muscle glycogen stores were extremely depleted. During four hours of recovery, subjects were provided with 4g carbohydrate per kilogram body weight from sports bars, gels, and carbohydrate-containing sports drinks. During recovery from the other trial, caffeine was added to the sports drink, providing 8mg per kilogram of body weight over the four-hour period.
As it turns out, Hawley was correct in his assumption that caffeine would enhance recovery. “With the ingestion of both caffeine and carbohydrate, the overall amount of glycogen stored in the muscle for the 4-hour period was 60-percent higher than with carbohydrate alone,” said Hawley. “There is absolutely no question that this additional muscle glycogen would improve performance.”
Blood glucose and blood insulin levels were also higher with the caffeine and carbohydrate test dose, and glucose transport into the muscle may also have been enhanced with the caffeine. “There was a more available pool of glucose and the caffeine may have tricked the glucose into entering the cell,” said Hawley. “Essentially it put more gas or petrol back in the engine.”
Before you start indulging in more $4 lattes, remember that this is only one study and it used a very high dose of caffeine for research purposes. When testing a new idea or theory, researchers often use a large amount of a substance to first see if there is an effect.
“For an athlete weighing 70-kilograms, this would be about 560 milligrams of caffeine,” said Hawley. “The dose we used is too high for athletes to use, and we now need to go back and complete a dose-response study.” In contrast a cola serving may provide 60 milligrams of caffeine, and 8 ounces of brewed coffee 100 milligrams. “Bottom line is that we have to do a dose-response to see if our initial findings have some practical application,” said Hawley.
So while this study provides the first evidence that caffeine co-ingested with carbohydrate after a bout of glycogen depleting exercise, this caffeine dose could also result in a number of side effects for triathletes, such as insomnia, jitteriness, and GI upset.
Monique Ryan, MS, RD, LDN is a nationally recognized nutritionist with over 24 years of experience and is owner of Personal Nutrition Designs, a Chicago based nutrition consulting company that provides nutrition programs for endurance athletes across North America (www.moniqueryan.com).