A systematic review of existing literature by researchers affiliated with the Georgia Institute of Technology and Georgia State University concludes that caffeine and carbohydrate significantly improve endurance exercise performance when taken before and/or during activity. The study was published in the February edition of the International Journal of Sports Nutrition and Exercise Metabolism.
The researchers conducted a meta-analysis of studies that were performed over the past 19 years through April of 2009. The studies were on human subjects with a crossover research design and had to include an endurance exercise bout that included a task (time to fatigue, time to complete a determined amount of work, or amount of work completed in set time), and both a carbohydrate and a carb + caffeine supplement.
The researchers defined endurance as an exercise test that was at least 10 minutes in duration, however, the range of the exercise durations were from 19-250 minutes. The supplementation had to take place no more than 90 minutes prior to exercise, during exercise, or both. So while the researchers found 140 studies for review, only 19 met the criteria for inclusion in the study.
After completing their analysis, the researchers found, “Carbohydrate plus caffeine provides a significant but small effect to improve endurance performance compared with carbs alone. However, the magnitude of the performance benefit that caffeine provides is less than when added to carbs than when added to placebo.”
There is still a lot of research to be done on the subject, however, the carbohydrate/caffeine combination is effective when it comes to increasing endurance.