Most studies on the performance enhancing benefits of caffeine are done with experienced athletes. A new one published in the Journal of Strength and Conditioning Research uses recreational runners and popular caffeine-containing energy drinks. Let’s see how much time it cut off their 5K effort.

Thirteen men and 8 women in their early 20s consumed a 500 ml energy drink or non-caffeinated sugar-free placebo an hour before running 5 km on a treadmill. Subjects switched drinks and repeated the race 7 days later. There were no differences in rate of perceived effort, but the energy drink helped runners finish an average of 10 seconds faster.