title: Caffeine withdrawal and high-intensity endurance cycling performance.
abstract: In this study, we investigated the impact of a controlled 4-day caffeine withdrawal period on the effect of an acute caffeine dose on endurance exercise performance. Twelve well-trained and familiarized male cyclists, who were caffeine consumers (from coffee and a range of other sources), were recruited for the study. A double-blind placebo-controlled cross-over design was employed, involving four experimental trials. Participants abstained from dietary caffeine sources for 4 days before the trials and ingested capsules (one in the morning and one in the afternoon) containing either placebo or caffeine (1.5 mg · kg(-1) body weight · day(-1)). On day 5, capsules containing placebo or caffeine (3 mg · kg(-1) body weight) were ingested 90 min before completing a time trial, equivalent to one hour of cycling at 75% peak sustainable power output. Hence the study was designed to incorporate placebo-placebo, placebo-caffeine, caffeine-placebo, and caffeine-caffeine conditions. Performance time was significantly improved after acute caffeine ingestion by 1:49 ± 1:41 min (3.0%, P = 0.021) following a withdrawal period (placebo-placebo vs. placebo-caffeine), and by 2:07 ± 1:28 min (3.6%, P = 0.002) following the non-withdrawal period (caffeine-placebo vs. caffeine-caffeine). No significant difference was detected between the two acute caffeine trials (placebo-caffeine vs. caffeine-caffeine). Average heart rate throughout exercise was significantly higher following acute caffeine administration compared with placebo. No differences were observed in ratings of perceived exertion between trials. A 3 mg · kg(-1) dose of caffeine significantly improves exercise performance irrespective of whether a 4-day withdrawal period is imposed on habitual caffeine users.
authors.affiliation: School of Public Health, Griffith University, Gold Coast, Queensland, Australia. c.irwin@griffith.edu.au
authors.forename: Christopher
authors.initials: C
authors.lastname: Irwin
authors.forename: Ben
authors.initials: B
authors.lastname: Desbrow
authors.forename: Aleisha
authors.initials: A
authors.lastname: Ellis
authors.forename: Brooke
authors.initials: B
authors.lastname: O'Keeffe
authors.forename: Gary
authors.initials: G
authors.lastname: Grant
authors.forename: Michael
authors.initials: M
authors.lastname: Leveritt
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology*; D003069:Coffee / Q000737:chemistry*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000187:drug effects*; D055815:Young Adult
chemical_list: D003069:Coffee; D002110:Caffeine