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Time of day could affect the body's response to exercise

Nighttime exercise could produce different results than daytime exercise

Photo (c) lzf - Getty Images
For many consumers, working out happens whenever there’s a free moment, whether that’s early in the morning or later in the evening.

While working out is the bottom line, a new study found that the time of day consumers choose to exercise could be affecting their results down the line.

“There appears to be significant differences between the effect of exercise performed in the morning and evening, and these differences are probably controlled by the body’s circadian clock,” said researcher Joshua Thue Treebak.

Morning versus evening

To see how exercising at different times of day affects the body, the researchers had mice exercise both during the early morning hours and then later in the evening, and then evaluated their muscle function and overall health.

The good news for consumers is that there isn’t a best time to work out -- the body doesn’t get an added benefit by exercising in the morning or in the evening. However, the researchers did find significant differences in the muscles when the mice exercised in the morning hours versus when they worked out later at night.

“Morning exercise initiates gene programs in the muscle cells, making them more effective and better capable of metabolising sugar and fat,” Treebak said. “Evening exercise, on the other hand, increases whole body energy expenditure for an extended period of time.”

While morning workouts were associated with better muscle cell function, which the researchers attribute to the body’s natural circadian clock, nighttime workouts were associated with increased energy expenditure, which affects how many calories we burn on a daily basis. 

Ultimately, the researchers don’t want to push consumers to work out at one time over another, as the study did not yield a clear cut winner -- simply differences between the different times of day.

“On this basis, we cannot say for certain which is best, exercise in the morning or exercise in the evening,” Treebak said. “At this point, we can only conclude that the effects of the two appear to differ, and we certainly have to do more work to determine the potential mechanisms for the beneficial effects of exercise training performed at these two time-points.”

Finding the right timing

As this study revealed, our circadian clocks control not only our sleeping patterns, but they can also influence our exercise results. A recent study found that the best time to exercise could vary from person-to-person depending on whether you identify as an early bird or a night owl.

“Circadian rhythms dominate everything we do,” said researcher Paolo Sasone-Corsi. “Previous studies from our lab have suggested that at least 50 percent of our metabolism is circadian, and 50 percent of the metabolites in our body oscillate based on the circadian cycle. It makes sense that exercise would be one of the things that’s impacted.”

Those that prefer a nighttime workout can rest assured that their sleep will not be compromised, as a recent study found that exercising at night does not disrupt sleeping habits -- so long as it’s not intense physical activity.

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