In a new study, researchers found exercise could shift the human body clock.
The direction and amount of this effect depend on the time of day or night in which people exercise.
The research was conducted by researchers at the University of California, San Diego, and Arizona State University.
The circadian “body”‘ clock is the 24-hour cycle that regulates many physiological processes including sleeping and eating.
Previous studies have shown that many factors could affect the body clock including light and time cues.
Exercise has been known to cause shifts in the body clock however very little is known about this effect.
In the current study, the team examined body clocks following exercise in 101 participants for up to five and a half days.
The baseline timing of each participant’s body clock was determined from urine samples collected every 90 minutes.
The team measured the time of the evening rise in melatonin and the peak of melatonin several hours later.
The participants then walked or ran on a treadmill at a moderate intensity for one hour per day for three consecutive days.
They exercised at one of eight different times of day or night, but each individual exercised at the same time on all three days or nights.
The timing of the body clock was re-assessed following the third exercise session.
The researchers found exercising at 7 am or between 1 and 4 pm advanced the body clock to an earlier time.
In addition, exercising between 7 and10 pm delayed the body clock to a later time.
Exercising between 1 and 4 am and at 10 am, however, had little effect on the body clock, and the phase-shifting effects of exercise did not differ based on age nor gender.
The findings suggest that exercise could counter the effects of jet lag, shift work, and other disruptions to the body’s internal clock.
But the team warns that the people tested were more physically active than average, the results might not translate to the average person.
In the future, the team will look at combining exercise with bright lights and melatonin to see what impact this has on body clocks.
They will also examine the effect of changes in exercise duration and intensity on the body clock.
The lead author of the study is Shawn Youngstedt. The study is published in The Journal of Physiology.
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Further reading: The Journal of Physiology.
