PURPOSE: A caffeine-mediated dose-response placebo effect has previously been observed in trained cyclists. The current study aimed to determine if perceived caffeine dose influences cognitive and/or running performance in recreational athletes.

METHODS: Twenty-nine healthy individuals (23.7±5 y (Mean±SD), 16 males) completed two morning trials (repeated measures design, separated by 1 week), involving a choice reaction time (CRT) test followed by a 10km performance run. Prior to the first trial, participants indicated their beliefs of caffeine’s effects on performance and any previous experience using caffeine as an ergogenic aid. On arrival to the testing facility, participants randomly received (and were told they were getting) “Low dose (100mg)” or “High dose (300mg)” of caffeine capsules (all contained placebo, (psyllium husk powder)) prior to commencing the CRT test (30min post capsule ingestion). Paired samples t tests were used to determine differences between trials and CRT latency (employing Ex-Gaussian analysis) and running performance using the entire participant sample and for the sub-groups exhibiting strong “beliefs” +/- prior experience.

RESULTS: Perceived caffeine dose did not influence CRT (μ-, σ- and τ-components respectively, Low: 400±53ms vs High: 388±4ms; Low: 35±18ms vs High: 34±17ms; Low: 50±24ms vs High: 52±19ms, all p’s>0.05). Neither personal belief (n=9), nor belief + experience (n=6) influenced this effect. Furthermore, perceived caffeine dose did not influence run time (Low: 49.05±3.75 min vs High: 49.06±3.85 min, p=0.979). Personal belief (Low: 48.93±3.71 min vs High: 48.9±3.52 min, p=0.976), and belief + experience (Low: 48.68±1.87 min vs High: 49.55±1.75 min, p=0.386) did not influence this effect.

CONCLUSIONS: Placebo effects of perceived caffeine-dose ingestion on cognitive and running performance were not observed in this study of recreationally active individuals, irrespective of individual’s prior beliefs or caffeine use.