Placebo effects of caffeine on short-term resistance exercise to failure.Int J Sports Physiol Perform. 2009 Jun; 4(2):244-53.IJ
This study examined the placebo effect of caffeine on number of repetitions (reps), rating of perceived exertion (RPE), blood pressure (BP), and peak heart rate (PHR) during resistance-training exercise with repetitions (reps) performed to volitional failure.
Following determination of 1-rep maximum in single-leg leg extension, 15 males performed reps to failure at 60% 1-RM in 3 conditions: control, perceived caffeine condition, and perceived placebo condition presented in a randomized order. Participants were informed they would ingest 250 mL of solution that contained either 3 mg.kg(-1) caffeine or 3 mg.kg(-1) placebo 1 h before each exercise trial. A deceptive protocol was employed and subjects consumed a placebo solution in both conditions. During each condition, total reps, RPE for the active muscle and overall body, and PHR were recorded.
Subjects completed 2 more reps when they perceived they had ingested caffeine. RPE was significantly (P=.04) lower in the perceived caffeine and control conditions and RPE for the active muscle was significantly higher across all conditions compared with RPE for the overall body. No substantial differences were evident in PHR across conditions.
Results of this study are similar to studies of actual caffeine ingestion. However, the perception of consuming a substance that purportedly enhances performance is sufficient enough to enable individuals to complete a greater number of reps to failure during short-term resistance exercise.