2.3. Study Design and Basic Measurements
BLIND, COMPLICATIONS
This research was a randomized, double-blind, placebo-controlled, crossover design study. Before the implementation of the intervention, the participants were familiarized with the research process during a theoretical session. Also, the benefits and possible risks were explained to them. Then, participants completed the Physical Activity Readiness Questionnaire (PAR-Q) and the consent form for participation in the research (including full descriptions of the implementation method, benefits, risks, and possible complications). The height (Seca 217, Hamburg, Germany), weight, and fat percentage (InBody 270) of each participant were also measured in the familiarization session. Then, the participants were randomly divided into three different conditions of placebo (PLA), low-dose caffeine (3 mg/kg BW) (C3), and high-dose caffeine (6 mg/kg BW) (C6), with a crossover design, and performed three separate sessions of exercise testing with a one-week wash-out. The half-life of caffeine is reported to be approximately 6 h [It should be noted that researchers were blinded to the conditions of each participant in the current study by an expert using the method of shuffling cards. In this method, the expert assigned the participants to three different conditions with codes 1, 2, and 3. The researchers did not know which condition was assigned to the PLA, C3, or C6. In addition, capsules of the same shape and size were used for each condition so that the participants were blind to each other’s condition. All participants were informed that they were taking a safe dose of caffeine.