Should I exercise in the morning or the evening? New research on physical activity and sleep architecture being presented today at the 58th Annual Meeting of the American College of Sports Medicine and the 2nd World Congress on Exercise is Medicine® may finally answer that age-old question. For the best sleep, researchers say, work out in the morning.

"Insufficient sleep threatens our country's health by contributing to chronic diseases, such as diabetes, cardiovascular disease and obesity," said Scott Collier, Ph.D., FACSM, lead author of the study. "Exercise is proven to improve the quality of sleep, and our team wanted to see if the timing of exercise could maximize these benefits."

Researchers with Appalachian State University studied the effects of exercise timing on the sleep patterns of six male and three female subjects. Each subject visited the lab on three separate occasions at pre-determined times - one at 7 a.m., one at 1 p.m. and one at 7 p.m. - for 30 minutes of treadmill exercise. At night, subjects wore a sleep-monitoring headband to measure sleep stage time and quality of sleep.

Aerobic exercise at 7 a.m. invoked significantly greater improvements in quality of sleep compared to exercise at 1 p.m. and 7 p.m. When subjects exercised in the morning, they spent more time in light sleep by 85 percent and more time in deep sleep by 75 percent. Exercising at 7 a.m. also caused a 20 percent increase in sleep cycle frequency.

"Our research has shown that well-timed exercise can elicit even greater sleep quality," said Collier, who is an assistant professor at Appalachian State University. "These findings - if the results of the sample hold true for the general population - can help exercisers gain even greater benefits from physical activity."

The National Sleep Foundation suggests adults get seven to nine hours of sleep per day, but nearly 25 percent of people in the U.S. do not get enough sleep. For more information on the importance of sleep, visit the U.S. Centers for Disease Control and Prevention.

American College of Sports Medicine