Elsevier

Physiology & Behavior

Volume 58, Issue 6, December 1995, Pages 1287-1291
Physiology & Behavior

Article
Phase-shifting human circadian rhythms with exercise during the night shift

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Abstract

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 8 consecutive night shifts, whereas control subjects (N = 8) remained sedentary. All subjects wore dark welder's goggles when outside after the night shift until bedtime, and then slept in dark bedrooms. Sleep was delayed 9 h from baseline. Rectal temperature was continuously measured. There were fewer evening-types and more morning-types in the exercise group than in the control group, which should have made phase delay shifts more difficult for the exercise group. Nevertheless, a majority of the exercise subjects (63%) had large temperature rhythm phase delay shifts (> 6 h in the last 4 days relative to baseline), whereas only 38% of the control subjects had large shifts. An ANCOVA showed that, when morningness-eveningness was accounted for (as the covariate), the exercise group had a significantly larger temperature rhythm phase shift than the control group. As expected, there was a correlation between the temperature rhythm phase shift and morningness-eveningness in the control group, with greater eveningness resulting in larger phase shifts. However, there was no such relationship in the exercise group; exercise facilitated temperature rhythm phase shifts regardless of circadian type. These results suggest that exercise might be used to promote circadian adaptation to night shift work.

References (24)

  • R.E. Mistlberger

    Scheduled daily exercise or feeding alters the phase of photic entrainment in Syrian hamsters

    Physiol. Behav.

    (1991)
  • D. Dawson et al.

    Timed exposure to bright light improves sleep and alertness during simulated night shifts

    Sleep

    (1991)
  • C.I. Eastman

    Are separate temperature and activity oscillators necesary to explain the phenomena of human circadian rhythms?

  • C.I. Eastman

    Circadian rhythms of rats at the limits of entrainment and a phase-shift model of “spontaneous internal desynchronization” in humans

  • C.I. Eastman

    High intensity light for circadian adaptation to a 12-h shift of the sleep schedule

    Am. J. Physiol.

    (1992)
  • C.I. Eastman et al.

    Light treatment for sleep disorders: Consensus report. VI. Shift work

    J. Biol. Rhythms

    (1995)
  • C.I. Eastman et al.

    Circadian rhythm adaptation to simulated night shift work: Effect of nocturnal bright-light duration

    Sleep

    (1995)
  • C.I. Eastman et al.

    Dark goggles and bright light improve circadian rhythm adaptation to night-shift work

    Sleep

    (1994)
  • D.M. Edgar et al.

    Regularly scheduled voluntary exercise synchronizes the mouse circadian clock

    Am. J. Physiol.

    (1991)
  • A. Horne et al.

    Self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms

    Int. J. Chronobiol.

    (1976)
  • D.M. McNair et al.
  • P.J. Mitchell et al.

    Facilitating vs. conflicting bright light exposure during night shifts for circadian adaptation to delayed and advanced sleep schedule shifts

    Sleep Res.

    (1995)
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    Current address: Circadian Pacemaker Laboratory, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093.

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