You Might Want to Switch Your Workouts to the Afternoon [Body Blog]

Are you one of those people who wakes up at the crack of dawn to go to the gym? Or are you that person who loves to go out for a midnight run? If you like to exercise early in the morning or late at night, first of all, I admire your dedication to your exercise plan. But you might want to adjust it. A new study shows that afternoon may be the best time to exercise in order to help regulate our bodies’ natural clocks.

Now, this research, like lots of early-stage exercise studies, was done in mice. So it’s not guaranteed that the results can be directly applied to humans. But mice have been the key to uncovering lots of information about diet and exercise in humans, and although they’re obviously different from us, we’re more similar to mice than you might think.

Humans’ bodies, as well as those of mice, are governed by natural rhythms. This body clock, called the circadian rhythm, dictates when we feel sleepy and awake, but it also regulates our hearts, livers, brains, and other organs. Certain cells in our bodies are designed to receive signals from sources of light or darkness, indicating “day” or “night.” They send messages to the rest of the body, causing our organs to operate differently based on the time of day.

When humans still lived without electricity, these circadian rhythms likely went on mostly uninterrupted. But now, it’s easy for this rhythm to get thrown off. Seeing artificial light at night, which most of us do, confuses your natural rhythm because the body expects darkness. That’s a big part of the reason why getting up early for class feels so miserable to most of us – the artificial lights inside buildings tell your body it should still be awake at night.

Disturbances in the circadian rhythm have been shown to cause bigger problems than dozing off in your 9 a.m. class. People with out-of-sync circadian rhythms may have a higher risk for diabetes, obesity, certain types of cancer, memory loss, and mood disorders. Yikes.

So these scientists wondered – can exercise fix a “broken” circadian rhythm? They used mice that were missing a critical body clock protein, meaning that signals from their internal clocks rarely reached the rest of their bodies. The mice were given access to a running wheel. Some were allowed to run whenever they wanted, and others were allowed access to the wheel only in the early morning hours.

The scientists expected they would find benefits from early morning exercise, the favorite time of many athletes. After several weeks of running, all of the animals showed improvements in their circadian rhythms. But the mice who exercised in the afternoon showed the most beneficial effects.

Again, the researchers say they aren’t completely sure how this will translate to humans. They say that most of all, it’s just important to exercise, no matter what time of day. But they did say it’s probably not the best idea to exercise late at night – that can make it hard for you to fall asleep and disrupt your natural rhythms.

Have you tested out the effects of different exercise times for yourself? What time of day do you like to exercise most?

Garnet is a student at Columbia University in New York City. She is “that person” who starts dancing at a party when everyone else is standing around, and if there were a Facebook stalking Olympics, she would be a gold medalist. She also loves cheesy 90s music, and almost died of happiness when Vanilla Ice retweeted her. Once. Follow her on Twitter @garnethenderson.

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