title: Effect of a divided caffeine dose on endurance cycling performance, postexercise urinary caffeine concentration, and plasma paraxanthine.
abstract: This study compared the effects of a single and divided dose of caffeine on endurance performance and on postexercise urinary caffeine and plasma paraxanthine concentrations. Nine male cyclists and triathletes cycled for 90 min at 68% of maximal oxygen uptake, followed by a self-paced time trial (work equivalent to 80% of maximal oxygen uptake workload over 30 min) with three randomized, balanced, and double-blind interventions: 1) placebo 60 min before and 45 min into exercise (PP); 2) single caffeine dose (6 mg/kg) 60 min before exercise and placebo 45 min into exercise (CP); and 3) divided caffeine dose (3 mg/kg) 60 min before and 45 min into exercise (CC). Time trial performance was unchanged with caffeine ingestion (P = 0.08), but it tended to be faster in the caffeine trials (CP: 24.2 min and CC: 23.4 min) compared with placebo (PP: 28.3 min). Postexercise urinary caffeine concentration was significantly lower in CC (3.8 micro g/ml) compared with CP (6.8 micro g/ml). Plasma paraxanthine increased in a dose-dependent fashion and did not peak during exercise. In conclusion, dividing a caffeine dose provides no ergogenic effect over a bolus dose but reduces postexercise urinary concentration.
authors.affiliation: School of Exercise and Sport Science, University of Sydney, Lidcombe 1825, New South Wales, Australia.
authors.forename: Kylie J
authors.initials: KJ
authors.lastname: Conway
authors.forename: Rhonda
authors.initials: R
authors.lastname: Orr
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Stannard
mesh_terms: D000328:Adult; D001642:Bicycling; D002110:Caffeine / Q000008:administration & dosage* / Q000097:blood / Q000652:urine; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D010807:Physical Endurance / Q000187:drug effects*; D013806:Theophylline / Q000097:blood*
chemical_list: D002110:Caffeine; D013806:Theophylline; C021183:1,7-dimethylxanthine