How to ‘spring forward’ for daylight saving time without leaving your body and brain behind

By Matt Fuchs edited by Tanya Lewis

On Sunday at 2 A.M. local time, daylight saving time will begin in most U.S. states, and clocks there will spring forward by an hour. Research shows hospital admissions increase right after this annual clock change, and many people lose sleep for one week or longer. The time change can also exacerbate sleep disorders and depression.

But researchers have identified two behaviors that, when combined in the morning, may stabilize circadian rhythms and ease the transition.

Daylight, absorbed through the eyes in the early morning, activates a pair of pea-sized clusters of cells deep in the brain called the suprachiasmatic nucleus, or SCN. The SCN’s tiny dimensions belie its importance as the body’s primary alarm clock. It sends rhythmic signals to millions of other timekeepers—called peripheral clocks—located in almost every cell with a nucleus in the body. These cells, in turn, switch on genes that prepare our organs for the day’s action, such as consuming and digesting food.

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The light-triggered SCN has been called the body’s “master” clock. But recent research shows that light is just one of several factors that determine our internal sense of time; another is exercise. Karyn Esser, a physiologist at the University of Florida, and her colleagues have found that exercise in the early hours is a powerful cue for the body’s peripheral clocks in oxygen-sensing organs such as the muscles. And other researchers have made similar findings in studies related to the lungs and kidneys. “Healthy circadian rhythms require coordination of clock systems across the body,” Esser says.

Because light and exercise influence circadian rhythms separately through the SCN and peripheral clocks, respectively, scientists think that combining these cues—exercise and morning sunshine—may work better to shift internal clocks to the time of both cues than either light or exercise alone.

Shawn Youngstedt, a professor of exercise science at Arizona State University’s Edson College, and his colleagues tested this combination in a small sample of adults. The researchers found that it produced a larger shift in internal clock timing than just exercise or exposure to light (that was bright enough to simulate sunlight). The combination still needs to be tested in larger studies, Youngstedt says, but exercise “has a significant impact” on the body’s ability to adjust to time shifts.

And scientists know that forceful triggers at dawn help ensure a smooth dusk. The circadian clocks, once set in motion, start a precise countdown to that evening’s release of melatonin—the hormone that lulls us into a relaxed, ready-for-sleep state.

Exercise and daylight exposure may be synergistic in other ways: exercise causes the pupils of our eyes to dilate and capture more light, which could be especially helpful as eyes lose light sensitivity as people age.

Modern schedules and artificial light often interfere with people’s 24-hour biological cycles. Regular disruption to these cycles, or circadian rhythms, is linked to chronic diseases and premature death.

The loss of a single hour when clocks spring forward on March 8 may sound trivial, but the sudden mismatch between our internal clocks and external ones can compromise sleep, well-being, traffic safety and heart health.

To manage these risks, experts suggest you prepare for the transition a few days ahead by using the light-and-locomotion strategy. Wake up 15 to 20 minutes earlier each day from March 5 to 8 and go for an outdoor walk or jog one hour after waking up (indoor light typically isn’t bright enough to reset internal clocks). These incremental changes will acclimate your body to the clock change gradually.

The more body parts you exercise, the better, Esser explains. She suggests that you try to get a little out of breath by exercising at about 50 to 75 percent of full exertion.

This preparation is especially important for older people or those with chronic illnesses. Around age 40, people’s circadian rhythms start to lose flexibility, resulting in “longer adjustments to the clock change and higher probability of a problem,” Esser says.

Certain habits could negate the benefits of the light-and-locomotion strategy. Late-night food or bright light later in the day can shift rhythms later, just as mornings are brightening earlier, says Gad Asher, a biochemist at the Weizmann Institute of Science in Rehovot, Israel, who studies the body’s internal clocks.

After establishing an earlier, stronger circadian rhythm—and springing forward unscathed—don’t throw out your new light-and-exercise habit, Asher says. Keep your rhythm steady to maintain your health for the long haul. “What really matters is your daily habits going forward,” he says.

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