Phase-adjustment of human circadian rhythms by light and physical exercise (original) (raw)
Related papers
Daily exercise facilitates phase delays of circadian melatonin rhythm in very dim light
AJP: Regulatory, Integrative and Comparative Physiology, 2004
Daily exercise facilitates phase delays of circadian melatonin rhythm in very dim light. Shift workers and transmeridian travelers are exposed to abnormal work-rest cycles, inducing a change in the phase relationship between the sleep-wake cycle and the endogenous circadian timing system. Misalignment of circadian phase is associated with sleep disruption and deterioration of alertness and cognitive performance. Exercise has been investigated as a behavioral countermeasure to facilitate circadian adaptation. In contrast to previous studies where results might have been confounded by ambient light exposure, this investigation was conducted under strictly controlled very dim light (standing ϳ0.65 lux; angle of gaze) conditions to minimize the phase-resetting effects of light. Eighteen young, fit males completed a 15-day randomized clinical trial in which circadian phase was measured in a constant routine before and after exposure to a week of nightly bouts of exercise or a nonexercise control condition after a 9-h delay in the sleep-wake schedule. Plasma samples collected every 30 -60 min were analyzed for melatonin to determine circadian phase. Subjects who completed three 45-min bouts of cycle ergometry each night showed a significantly greater shift in the dim light melatonin onset (DLMO 25%), dim light melatonin offset, and midpoint of the melatonin profile compared with nonexercising controls (Student t-test; P Ͻ 0.05). The magnitude of phase delay induced by the exercise intervention was significantly dependent on the relative timing of the exercise after the preintervention DLMO 25% (r ϭ Ϫ0.73, P Ͻ 0.05) such that the closer to the DLMO 25%, the greater the phase shift. These data suggest that exercise may help to facilitate circadian adaptation to schedules requiring a delay in the sleep-wake cycle. circadian; jet lag; shift work SCHEDULED PHYSICAL ACTIVITY such as wheel running in rodents and exercise in humans has been reported to influence the circadian timing system. Wheel running (12, 31) and forced treadmill running (21, 24) have been reported to entrain circadian rhythms in hamsters (31) and mice (12, 21) and when the period of the free-running rhythm was close to the period of the treadmill schedule in rats (24). Several studies have assessed the effectiveness of exercise as a circadian phase-resetting agent in humans. Van Reeth et al. (34) reported that a single exercise bout, centered from 3 h before to 2 h after the body temperature minimum, phase delayed the human circadian rhythms of temperature and thyrotropin. In that study, exercise that consisted of 3 h of alternating arm and leg ergometry at 40 and 60% of maximal O 2 consumption (V O 2 max ) was performed under constant lighting conditions of Ͻ300 lux. Using the same protocol, Baehr and colleagues (1) reported similar phase delays between young and older adults. Another study reported that higher-intensity exercise of shorter duration, 1 h of stair climbing at 75% V O 2 max , centered at 0100 (in ϳ70 -80 lux), also elicited significant phase delays in the circadian rhythm of thyrotropin. Recently, this protocol was expanded to include scheduled morning, afternoon, evening, and night exercise sessions in ϳ40 lux (8). Significant phase delays were reported for noctural exercise, and significant phase advances were reported for evening exercise. Only one other study to date has reported that exercise can advance the human circadian pacemaker. In a shortened T-cycle protocol of twelve 23-h and 40-min cycles, subjects who performed two bouts of cycling and rowing at a heart rate of 140 beats/min during the morning and afternoon showed a 1.6-h advance in the peak of the plasma melatonin rhythm, whereas subjects in the nonexercise control condition averaged a 0.80-h phase delay of the melatonin peak (25).
Effects of physical exercise on human circadian rhythms
Sleep and Biological Rhythms, 2006
Bright light is the principal zeitgeber for the biological clock in mammals, including humans. But there is a line of evidence that non-photic stimuli such as physical activity play an important role in entrainment. Scheduled physical activity, such as wheel and forced treadmill running, has been reported to phase-shift and entrain the circadian rhythm in rodent species. In humans, several studies have reported the phase-shifting effects of physical exercise. A single bout of physical exercise at night was demonstrated to phase-delay the circadian rhythm in plasma melatonin. However, for the entrainment of human circadian rhythm, a phase-advance shift is needed. Previously, we demonstrated that scheduled physical exercise in the waking period facilitated the entrainment of plasma melatonin rhythm to the sleep/wake schedule of 23 h 40 min. This result suggested that timed physical exercise produced phase-advance shifts. A regular physical exercise also facilitated entrainment of the circadian rhythms associated with acute phase-delay shifts of the sleep/wake and light/dark schedule. These findings suggest that physical exercise is useful to adjust the circadian rhythm to external time cues, especially for totally blind people and elderly people.
Circadian phase-delaying effects of bright light alone and combined with exercise in humans
American journal of physiology. Regulatory, integrative and comparative physiology, 2002
In a within-subjects (n = 18), counterbalanced design, the circadian phase-shifting effects of 3 h of 1) bright light (3,000 lx) alone 2) and bright light combined with vigorous exercise were compared. For each treatment, volunteers spent 3 nights and 2 days in the laboratory, typically receiving the treatment from approximately 2300 to 0200 on night 2. Bedtimes and waketimes were fixed to the volunteers' habits. Illumination was 50 lx during other wake hours and 0 lx during sleep. Bright Light Alone elicited a significant phase delay in rectal temperature minimum (70 min), but not in urinary 6-sulphatoxymelatonin (6-SMT) acrophase (20 min). Bright Light + Exercise elicited a significant phase delay in 6-SMT (68 min), but did not result in a significant difference in shift compared with Bright Light Alone. The study had adequate statistical power (80%) to detect phase-shift differences between treatments of approximately 2-2.5 h. Thus any antagonism of light shifts with exercise...
American journal of physiology. Regulatory, integrative and comparative physiology, 2014
Our previous study demonstrated that physical exercise under dim lights (<10 lux) accelerated reentrainment of the sleep-wake cycle but not the circadian melatonin rhythm to an 8-h phase-advanced sleep schedule, indicating differential effects of physical exercise on the human circadian system. The present study examined the effects of bright light (>5,000 lux) on exercise-induced acceleration of reentrainment because timed bright lights are known to reset the circadian pacemaker. Fifteen male subjects spent 12 days in temporal isolation. The sleep schedule was advanced from habitual sleep times by 8 h for 4 days, which was followed by a free-run session. In the shift session, bright lights were given during the waking time. Subjects in the exercise group performed 2-h bicycle running twice a day. Subjects in the control kept quiet. As a result, the sleep-wake cycle was fully entrained by the shift schedule in both groups. Bright light may strengthen the resetting potency of t...
Phase-shifting human circadian rhythms with exercise during the night shift
Physiology & Behavior, 1995
Appropriately timed exercise can phase shift the circadian rhythms of rodents. The purpose of this study was to determine whether exercise during the night shift could phase delay the temperature rhythm of humans to align with a daytime sleep schedule. Exercise subjects (N = 8) rode a stationary cycle ergometer for 15 min every h during the first 3 of
The present study was undertaken to asses selected time of day effect on different parameters like oral temperature, respiratory rate, finger counting, time estimation, random number adding speed & random adding ratio. The parameters were recorded four times a day i.e. 07.00, 11.00, 15.00 & 19.00 hours for consecutive 4-7 days. Most performance measures were observed to show a natural sway during the solar day in close correspondence with curve in body temperature. Peak in oral temperature recorded at pm hours resembled the peak of respiratory rate that was also recorded at the same time. The detection of circadian rhythimicity in oral temperature; heart as well as self rating mood and activity all with acrophase between 14.20 and 16.28 hrs. It is thought that there are two major rhythms which have relevance for exercise and sports performance. These are the rhythm in body temperature regarded as fundamental variables and sleep-wake cycle by which humans order their work-rest and sleeping schedules.
AJP: Regulatory, Integrative and Comparative Physiology, 2010
Effects of timed physical exercise were examined on the reentrainment of sleep-wake cycle and circadian rhythms to an 8-h phase-advanced sleep schedule. Seventeen male adults spent 12 days in a temporal isolation facility with dim light conditions (<10 lux). The sleep schedule was phase-advanced by 8 h from their habitual sleep times for 4 days, which was followed by a free-run session for 6 days, during which the subjects were deprived of time cues. During the shift schedule, the exercise group ( n = 9) performed physical exercise with a bicycle ergometer in the early and middle waking period for 2 h each. The control group ( n = 8) sat on a chair at those times. Their sleep-wake cycles were monitored every day by polysomnography and/or weight sensor equipped with a bed. The circadian rhythm in plasma melatonin was measured on the baseline day before phase shift: on the 4th day of shift schedule and the 5th day of free-run. As a result, the sleep-onset on the first day of free-r...
2013
A huge thank-you to all those that made my journey what it was: To my family Shan, Warwick, Chad and Rory for their continual support, patience and love To my gran Ethel Moffett for many hours of proofreading To my two supervisors: Dr Dale Rae and Dr Laura Roden. Thank-you for teaching, guiding and always making time for me. I am very privileged to have experienced the supervisor-student relationship that I have been fortunate enough to have with both of you. Prof Tim Noakes-a hero and true inspiration Prof Mike Lambert for always having an open door To all of the runners, non-runners and swimmers who so willingly participated in my studies To an amazing and efficient support team at ESSM-Thanks for always helping and assisting me no matter how busy you were: Ayesha Hendricks, Neezaam Kariem, Trevino Larry and especially Lance Walbrugh To Lorraine McDonald and Adri Winckler for always ensuring that my paper work was up to date Bongiwe Ndamane-for being so helpful and patient To Marius and Shonee Cornelissen for kindly allowing me use the OM and SSISA swimming pools for swimming testing To Nyambura Shawa and Lovemore Kunorozva-not only for always willing to help and teach me in the laboratory, but more importantly for your invaluable friendship, continual support and for always making me laugh vii Department of Human Biology