Caffeine effects on VO 2 max test outcomes investigated by a placebo perceived-as-caffeine design

Background: Ergogenic effects of caffeine (CAF) ingestion have been observed in different cycling exercise modes, and have been associated with alterations in ratings of perceived exertion (RPE). However, there has been little investigation of maximal oxygen uptake (VO 2MAX ) test outcomes. Aim: This study aimed to verify whether CAF may reduce RPE, thereby improving maximal incremental test (MIT) outcomes such as VO 2MAX , time to exhaustion and peak power output (W PEAK ). Methods: Nine healthy individuals performed three MITs (25 W/min until exhaustion) in a random, counterbalanced fashion after ingestion of CAF, placebo perceived as caffeine (PLA), and no supplementation (baseline control). VO 2 was measured throughout the test, while RPE was rated according to overall and leg effort sensations. The power output corresponding to submaximal (RPE = 14 according to the 6–20 Borg scale) and maximal RPE was recorded for both overall (O-RPE 14 and O-RPE MAX ) and leg RPE (L-RPE 14 and L-RPE MAX ). Results: VO 2MAX did not change significantly between MITs; however, CAF and PLA increased time to exhaustion (↑ ∼18.7% and ∼17.1%, respectively; p < .05) and W PEAK (↑ ∼13.0% and ∼11.8%, respectively; p < .05) when compared with control. When compared with control, CAF ingestion reduced submaximal and maximal overall and leg RPEs, the effect being greater in maximal (likely beneficial in O-RPE MAX and L-RPE MAX ) than submaximal RPE (possibly beneficial in O-RPE 14 and L-RPE 14 ). Similar results were found when participants ingested PLA. Conclusions: Compared with control, CAF and PLA improved MIT performance outcomes such as time to exhaustion and W PEAK , without altering VO 2MAX values. CAF effects were attributed to placebo.