At baseline, study participants were randomized to receive caffeine or placebo at a 1:1 ratio, by independent statistician. Was used a completely randomized design for two treatments which PLAN procedure (SAS 9.4). The allocation was made for a person outside the study what identified the capsules in identical packages labeled with the name of the participants. The active (caffeine) and placebo (maize starch) capsules were identical in color, size, weight, and packaging.