title: Preliminary studies on the immediate phase-shifting effects of light and exercise on the human circadian clock.
abstract: The aim of the present research was to determine the magnitude and direction of immediate phase shifts of human rhythms following a single exposure to a 3-hr pulse of bright light or physical activity. The pulse of light or activity was presented under "constant-routine" conditions, and measurements of the resultant phase shifts were performed under the same constant-routine conditions on the first day following pulse presentation. Four overt rhythms that are strongly dependent on circadian timing--namely, the rhythms of plasma cortisol, plasma thyroid-stimulating hormone (TSH), plasma melatonin, and body temperature--were monitored. The analysis of the TSH profiles indicated that exposure to light at about the time of the minimum of body temperature resulted in phase advances averaging less than 1 hr in magnitude. Exposure to light approximately 3 hr before the time of the minimum of body temperature resulted in phase delays of 1-2 hr. Preliminary analyses of the melatonin profiles have confirmed these observations. Our findings regarding the effects of exercise are still inconclusive.
authors.affiliation: Department of Medicine, University of Chicago, Illinois 60637.
authors.forename: E
authors.initials: E
authors.lastname: Van Cauter
authors.forename: J
authors.initials: J
authors.lastname: Sturis
authors.forename: M M
authors.initials: MM
authors.lastname: Byrne
authors.forename: J D
authors.initials: JD
authors.lastname: Blackman
authors.forename: N H
authors.initials: NH
authors.lastname: Scherberg
authors.forename: R
authors.initials: R
authors.lastname: Leproult
authors.forename: S
authors.initials: S
authors.lastname: Refetoff
authors.forename: O
authors.initials: O
authors.lastname: Van Reeth
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D001831:Body Temperature / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D003071:Cognition / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008027:Light; D008297:Male; D008550:Melatonin / Q000097:blood / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D013972:Thyrotropin / Q000097:blood / Q000502:physiology
chemical_list: D001786:Blood Glucose; D013972:Thyrotropin; D008550:Melatonin; D006854:Hydrocortisone