title: Effects of daytime ingestion of melatonin on short-term athletic performance.
abstract: The immediate effects of ingesting melatonin in the daytime include decreased alertness and body temperature. To date, no researcher has examined whether daytime ingestion of melatonin leads to impairments in variables relevant to short-term (<10 min) athletic performance. Twelve physically active participants (mean +/- s age = 25.2 +/- 5.0 years, body mass = 81.4 +/- 12.1 kg and chronotype = 33.8 +/- 6.3 units) ingested 5 mg of melatonin or placebo at 11:45 hours in a double-blind experiment. At 13:00 and 17:00 hours, subjective alertness was measured, together with intra-aural temperature, reaction time (two-, four- and eight-choice), short-term memory recall and grip strength. Performance, ratings of perceived exertion (RPE) and heart rate were also recorded during a 4-km cycling time trial. At 13:00 hours, the mean +/- s intra-aural temperature was 0.49 +/- 0.79 degrees C lower after ingestion of melatonin than after placebo (p = 0.015), but this difference was not apparent at 17:00 hours. At both 13:00 and 17:00 hours, melatonin reduced (p < 0.05) alertness, short-term memory and exercise heart rate by 1.5 +/- 1.8 units, 1 +/- 1 digits and 6 +/- 9 beats.min(-1), respectively (mean +/- s). Eight-choice reaction time was also slower at both times of day after ingesting melatonin. Melatonin did not influence time trial performance or RPE (p > 0.05). The effects of 5 mg of melatonin seem more pronounced for mental rather than physical components of short-term athletic performance, although the cardiovascular responses to exercise are affected. Some effects of melatonin were apparent 5 h after ingestion when the hypothermic effects of melatonin had dissipated.
authors.affiliation: Research Institute for Sport and Exercise Science, Liverpool John Moores University, 15-21 Webster Street, Liverpool L3 2ET, UK. G.Atkinson@livjm.ac.uk
authors.forename: G
authors.initials: G
authors.lastname: Atkinson
authors.forename: H
authors.initials: H
authors.lastname: Jones
authors.forename: B J
authors.initials: BJ
authors.lastname: Edwards
authors.forename: J M
authors.initials: JM
authors.lastname: Waterhouse
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001831:Body Temperature / Q000187:drug effects; D002940:Circadian Rhythm / Q000502:physiology*; D004311:Double-Blind Method; D004424:Ear Canal / Q000502:physiology; D018737:Hand Strength / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008550:Melatonin / Q000008:administration & dosage* / Q000494:pharmacology; D008570:Memory, Short-Term / Q000187:drug effects; D005082:Physical Exertion / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D013997:Time Factors
chemical_list: D008550:Melatonin