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When Should You Exercise If You Work Shifts or Have Jet Lag?

By Jiri Kaloc

Exercise can make changes to your body’s internal clock. It can affect when you get sleepy and when you get up. A recent study helped us understand when exercise moves the body clock forward and when back. If you’re a shift worker, go through jet lags often, or just want to improve your sleep routine, read on.

Professor Shawn Youngstedt at the Arizona State University, College of Nursing and Health Innovation, and his co-authors Jeffrey Elliott and Daniel Kripke wanted to expand on research that had shown exercising can cause changes to the body’s circadian rhythm. They decided to examine exercise at 8 different times of the day or night in 101 subjects. Their study from February 2019 was the largest of its kind and the first one to compare women against men and older adults against young adults. They found that neither sex nor age made a difference in how exercise shifts the body clock.

Exercise between 1:00 and 4:00 or at 10:00 had little effect on the body clock. © Profimedia

“We know that it can affect the internal clock but there was never a clear understanding of what time of day exercise causes delays and when exercise advances the body clock. Without knowing this information, it is more difficult to help people who have body-clock disturbances,” said Shawn Youngstedt.

These are their findings

  • Exercise at 7:00 or between 13:00 and 16:00 advanced the body clock, which would help people start activities earlier the next day.
  • Exercise between 19:00 and 22:00 delayed the body clock, which would help people shift their peak performance later the next day.
  • Exercise between 1:00 and 4:00 or at 10:00 had little effect on the body clock.

So, if you’re trying to go to bed earlier because of shift work or a change of a time zone, it might be helpful to exercise early in the morning or in the early afternoon. If you need to postpone your bedtime, exercising in the late evening is the way to go.