Physical Exercise

1 hour of moderate treadmill exercise causes a significant circadian phase shift, i.e. an advance or delay of your inner clock, as shown by a recent study.1 The respective effect depends on exercise timing: Similar to light exposure, phase advances can be achieved early in the morning as well as early afternoon [1-4 p.m.], while evening exercise [7-10 p.m.] causes a delay. Peak times for maximum effectiveness show a mean phase shift of 0.5-1.0 hours with standard deviations of similar magnitude.

Physical exercise at different times of day shifts your inner clock into different directions with varying magnitude. This figure represents the observed shifts after 1-hour of moderate treadmill exercise at different (biological) daytimes.

There is reason to assume that magnitude of the phase shifts positively correlates with intensity and duration of the exercise: 90 minutes of exercise between 10:10 p.m. and 11:40 p.m. at 65%-75% of maximum heart rate were shown to cause 84% of the delay that induced by an equally timed exposure to 5000 lux of light, which is believed to be the most important zeitgeber.1,2



[1] Youngstedt, S. D., Elliott, J. A., & Kripke, D. F. (2019). Human circadian phase–response curves for exercise. The Journal of Physiology, 597(8), 2253–2268.
Over the course of 5.5 days in the lab, 99 adults (48 young, 51 older) were split up into time slots and performed 1h of moderate treadmill exercise at the respective time for 3 consecutive days.

[2] Blume, C., Garbazza, C., & Spitschan, M. (2019, September 1). Effects of light on human circadian rhythms, sleep and mood. Somnologie. Dr. Dietrich Steinkopff Verlag GmbH and Co. KG.