No Detectable Effect of Caffeine Expectancy Induced by a Placebo Capsule on Time to Exhaustion at the Respiratory...

This study aimed to analyze the placebo effect associated with caffeine ingestion on cycling performance at the respiratory compensation point (RCP). Nineteen trained male cyclists (age: 28.1 ± 9.4 years; body mass: 71.0 ± 8.4 kg; VO₂max: 67.1 ± 6.7 mL·kg^-1·min^-1) completed two time-to-exhaustion (TTE) tests at the power output associated with RCP under two conditions: caffeine informed/placebo ingested (Expectancy) and non-ingested (Control), separated by 4-7 days. Total work (kJ) was recorded as the main performance variable and heart rate and rating of perceived exertion were measured. The side effects were evaluated through a questionnaire administered the day after the expectancy condition. TTE performance was similar (157.31 ± 63.45 kJ Expectancy vs. 154.83 ± 56.19 kJ Control, p = 0.68, trivial d = 0.09). Heart rate did not differ between trials (173.05 ± 9.65 bpm vs. 173.32 ± 9.74 bpm, p = 0.71 trivial d = -0.07), and RPE reached maximal values. Mild side effects-mainly increased activeness and muscular pain (31.3%)-were reported following placebo ingestion. In conclusion, this study did not detect an effect of a caffeine expectancy manipulation on time to exhaustion at the RCP in trained male cyclists. Heart rate was similar between conditions, and mild subjective symptoms were reported following the expectancy condition, although these cannot be causally attributed to expectancy.