Anecdotally speaking, have you noticed that you feel better during and after training when you’ve put some caffeine in the tank? Research reported in the June issue of Medicine
& Science in Sports & Exercise (2015; 47 , 1145–58) confirmed that while caffeine improves endurance exercise performance, the ergogenic mechanism(s) behind this effect remain unclear.
Researchers found that consuming a dose of 5 milligrams of caffeine per kilogram of body weight (about 2–3 cups of coffee, depending on your size and the type of coffee) before a training bout improved cycling performed with the legs. However, the same dose did not improve cycling performance for subjects using upper-body ergometers (“pedaling” with the arms). Researchers ascribed this difference to the fact that caffeine provided strength gains in subjects’ legs but not in their arms, likely because more muscle was turned on in the legs.
A second part of the experiment showed that when researchers controlled how the exercises were performed (cycling with arms or legs for 30 minutes) and suggested that exercisers cycle at about 60% of maximal ability, subjects experienced lower levels of perceived exertion and less muscle pain. When exercise intensity rose, neither perception of effort nor pain levels decreased.