Purpose: The objectives were to determine the effects of time-of-day consumption and training status on the benefits of caffeine supplementation for cycling performance and peak muscle strength. METHODS: Twenty untrained and trained subjects completed four trials consisting of isokinetic peak torque testing and 3-km time trials (TT). Subjects ingested either 6 mg/kg of caffeine or a placebo one hour prior to each trial. Treatments were: morning + placebo, morning + caffeine, evening + placebo, evening + caffeine. Magnitude based inferences were used to evaluate treatment differences. RESULTS: Caffeine (‘very likely’ and ‘likely’) improved 3-km TT performance in the morning and evening. 3-km TT performance was ‘likely’ improved more in the morning than evening for total subject pool and trained subjects. Untrained subjects ‘likely’ benefited more during the 3-km TT from supplementation than trained in both the morning and evening. Caffeine supplementation was ‘likely’ trivial and ‘unclear’ for the majority of peak muscle strength conditions. CONCLUSIONS: Caffeine supplementation improved 3-km TT performance in the morning for trained and untrained, with lesser benefits in the evening, while untrained benefited more than trained. Peak muscle strength was largely unaffected by caffeine supplementation, regardless of time-of-day consumption or training status
