The Best Time to Exercise?

December 19th, 2012 by Andrea Bennett

Is there really an ideal time of day to break a sweat?

Brought to you by Liberty Mutual's
The Responsibility Project

We’re closing in on a new year, when gym memberships soar, that infrequently used juicer gets dusted off, and people everywhere (myself included) start thinking of ways to make time for a little bit of healthy physical activity.

As such, it’s no surprise that the most-read article in the health section of The New York Times recently was about the ideal time of day to exercise. According to a study by researchers at the University of California, Los Angeles’s Brain Research Institute, which appears in the December Journal of Physiology, exercise does affect our circadian rhythms, and the effect may be most beneficial if you exercise in the afternoon.

As the NYT article details, the researchers set out to evaluate the potential health consequences of an out-of-whack circadian rhythm – which involves, among other body parts, a cluster of cells inside the brain whose job it is to tell the time of day. Your internal clock can become discombobulated by viewing artificial light in the evening, or even by aging, and research has linked out-of-sync circadian rhythms to an increased risk for diabetes, obesity, certain types of cancer, memory loss and depression.

To evaluate whether exercise could “fix” circadian rhythms, the researchers studied both healthy mice and those unable to produce a critical protein to regulate their circadian rhythm. They put both sets on running wheels during certain times of the day and left some sedentary. While the running mice began producing more proteins in their internal-clock cells at any hour than the non-runners, the biggest improvement was among the internally challenged mice running in the afternoon.

It might be some evidence that running in the afternoon is better for you. Of course, the generally accepted wisdom is that exercise is best whenever you can get it. According to the American Heart Association, the benefits of exercise aren’t just limited to the time of day you do it, but the level of physical activity, location and even your social setting (which can help you be more consistent).

So until there’s definitive proof that there’s one perfect formula for the optimal workout, it seems that just showing up is still, at least, the first step. Have some great tips on getting started on a 2013 health plan? Share them here.