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Surprising Science

Why Afternoon is the Best Time to Exercise

The ability of exercise to improve how our body clocks run may be especially effective in the afternoon, say researchers at UCLA’s Brain Research Institute who studied how exercise affects mice. 

What’s the Latest Development?

Researchers at UCLA’s Brain Research Institute believe that exercising at the right time of day may contribute to a well-regulated body clock thanks to higher levels of protein production in the brain. Their new conclusions are the result of experiments in which mice exercised at different times during the day. “After several weeks of running, the animals’ internal clocks were sturdier. Messages now traveled to these animals’ hearts and livers far more frequently than in their sedentary counterparts. The beneficial effect was especially pronounced in those animals that exercised in the afternoon (or mouse equivalent).”

What’s the Big Idea?

While scientists can’t say for sure that humans should exercise in the afternoon rather than the morning (any exercise is better than none), they do recommend against exclusively late-night activity: “Unpublished results from [the study] show that healthy mice running at the animal equivalent of 11 p.m. or so developed significant disruptions in their circadian rhythm. Among other effects, they slept poorly.” Still, if you wish to sleep well and avoid physical ailments associated with aging or clumsy circadian rhythm, exercise remains a very good idea. 

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