Afternoon Exercise Might Be Best Your body's circadian rhythms will thank you, study says By John Johnson, Newser Staff Posted Dec 12, 2012 6:43 PM CST 4 comments Comments (Shutterstock) (Newser) – Is it better to work out in the morning or afternoon? A new study suggests that those who exercise in the afternoon might be doing their bodies a bigger favor, reports the New York Times. The research involving mice suggests that mid-day exercise helps keep the body's internal clock, or circadian rhythms, in sync—a feat that gets more important as we age, with "serious potential health consequences" at stake, says the study's lead scientist. Mice that were bred to have defective internal clocks were able to repair them if they ran in the afternoon as opposed to any other time. Researchers aren't yet suggesting that early-rising joggers shift to the afternoon. “If you like morning exercise, which I do, great. Keep it up," says the lead researcher. But they're more confident in their advice to anyone who likes to exercise late at night: Get it done earlier.