title: The effects of evening bright light exposure on subsequent morning exercise performance.
abstract: We investigated the effects of evening bright light on the circadian timing of core temperature and morning exercise performance under conditions of high thermal stress. At 20:00 h, 8 males were exposed to a standardised light protocol and thereafter to either polychromatic bright light (2,500 lux at 50 cm, BL) or no light (0 lux, NL) for 30 min. The following morning, intermittent cycling exercise was undertaken followed by a 10 km time-trial in an environmental chamber set to 35°C and 60% relative humidity. Core body temperature was measured throughout. Data were analysed using a within-subjects model and presented as mean±SD. Time of the sleep-trough in core temperature occurred ~1.75 h later following BL (P=0.07). Prior to time-trial, core temperature was 0.27±0.42°C lower in BL (95%CI: -0.02 to 0.57, P=0.07). The time-trial was completed 1.43±0.63 min (0.98-1.87) faster in BL (P=0.001). Post time-trial, intestinal temperature was 38.21±0.56°C (37.84-38.57) in BL compared to 38.64±0.42°C (38.34-38.93) in NL (P=0.10). These data provide the first evidence that a 30-min exposure to bright light prior to sleep can influence exercise performance under hot conditions during the subsequent early morning.
authors.affiliation: Molecular and Clinical Pharmacology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Thompson
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: H
authors.initials: H
authors.lastname: Jones
authors.affiliation: School of Public Health, University of São Paulo, São Paulo, Brazil.
authors.forename: E
authors.initials: E
authors.lastname: Marqueze
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: W
authors.initials: W
authors.lastname: Gregson
authors.affiliation: Health and Social Care Institute, Teesside University, Middlesbrough, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Atkinson
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology; D001833:Body Temperature Regulation; D002940:Circadian Rhythm; D006358:Hot Temperature; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*; D012463:Saliva / Q000378:metabolism; D012890:Sleep; D055815:Young Adult
chemical_list: D008550:Melatonin