Caffeine effects on VO 2max 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.