Sleep vs. Exercise?

Q. For working parents, it’s difficult to find time to exercise during the week, and early morning is often the only time slot available. Is it better for my overall health to get eight hours of sleep per night during the week but not have time to exercise, or to get six and a half to seven hours of sleep per night and fit in a morning workout?

A. “That’s a terrible choice,” said Dr. Charles Czeisler, a sleep expert at Brigham and Women’s Hospital and Harvard Medical School in Boston. Both sleep and exercise are key components of a healthy lifestyle and shouldn’t be pitted against each other, Dr. Czeisler said.

Sleep is important for workouts, he noted, reducing the risk of injury and allowing muscles to recover from exercise. Lack of sleep weakens the immune system, making people more likely to become sick — which means missing workouts. Sacrificing sleep has also been tied to weight gain, cardiovascular disease and diabetes, among other health problems. Of course, regular exercise provides a lot of benefits, too, including sounder sleep.

Dr. Czeisler also noted that going to bed late, particularly if you’re using electronic devices and sitting under bright lights before bedtime, shifts the body’s circadian rhythms later. But people still need around eight hours of sleep per night. So if you get up after six and a half hours to work out, “you’re essentially exercising during your biological night,” he said.

Research from Northwestern University suggests that muscle cells also have circadian rhythms, and that they perform and recover much better during the biological daytime than the biological night. “So, getting up during your biological night to exercise is counterproductive,” Dr. Czeisler said.

Desiree Ahrens, a certified health and wellness coach at the Mayo Clinic in Rochester, Minn., said that for the time-starved, there are ways to sneak exercise into the day without heading to the gym or a formal exercise class.

Running up the stairs in your house provides just as much exercise as a workout on a stairclimber, she noted. Workouts can also be broken down into small chunks of activity throughout the day. “Be a little more creative with the workouts,” she suggested.

Also, if you have young children at home, it’s O.K. to acknowledge that these may not be the most workout-intensive years of your life, Ms. Ahrens said. No need to catastrophize and worry you’ll never exercise again.

Mostly, Ms. Ahrens advised, use common sense when striking a balance between getting enough sleep and getting up for a morning workout.

“If you have all the best intentions and you end up waking up three times that night with the kids,” she said, “go back to sleep.”