WASHINGTON, Nov. 24 — Older women who often have trouble sleeping may want to consider a little workout in the morning for a better rest at night. Morning exercisers had fewer complaints about a bad night’s sleep and those who stretched in the morning had somewhat better sleep, a new study found. Women who exercise in the evening, on the other hand, were more likely to be up at night.
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The women didn't need much morning activity to get the benefit. “It’s like doing a brisk walk,” said researcher Anne McTiernan. “Nobody is saying people have to be athletes and do marathons.”
The scientists at Fred Hutchinson Cancer Research Center in Seattle drew their data from a larger study of the effects of exercise in reducing the risk of breast cancer. Because the study included survey questions on sleep, the researchers could examine an issue that was not part of the original project. McTiernan is principal investigator of the cancer study as well as senior researcher on the sleep project, whose findings were published in the November issue of the journal Sleep.
Women in the sleep study were cancer-free and postmenopausal, ages 50 to 75, overweight or obese, and not exercising at the start of the project. Eighty-seven were placed in the exercise program and 86 in the stretching program. Both groups were followed for a year. Researchers compared how well the women reported sleeping before the study started and afterward.
Women in the exercise program did at least 45 minutes of moderate walking or riding an exercise bike five days a week at an exercise facility or on their own. Those who were stretching did an hour once a week under the supervision of an exercise physiologist, and stretched 15 to 30 minutes three times a week on their own. Fifty-five percent of all the women did their activity in the morning.
Although the exercise program was about 15 minutes a day more than federal officials recommend as the minimum for healthful exercise, it’s still not a lot, McTiernan said. The heart rates of the exercisers were no higher than they would get in a brisk walk, she said.
Significant improvement reported
How the women did in their programs was compared with their ratings of their ability to sleep, including whether they used sleep aids such as pills or alcohol, whether they felt they were sleeping soundly and through the night, and whether they fell asleep during quiet activities.
Women who exercised averaged 70 percent better sleep and women who stretched averaged 30 percent better sleep, the study found.
The study did not look for reasons why exercise in the morning was good for a night’s rest while exercise at night was not, or why stretching would help at all.
The researchers suspect that exercise in the morning might set the women’s body clocks for a day of activity and a night of sleep, while exercise at night might push back the sleep part of the sleep-wake cycle. They speculate that the stretches might have improved sleep by making the women more flexible and relaxed.
Exercise also increases activity hormones and creates lactic acid as a byproduct, and both can make a body more restless, said Edward Stepanski, director of the Sleep Disorders Service and Research Center at Rush University Medical Center in Chicago. Similarly, exercise raises temperature, while sleep requires a slight drop in temperature, said Stepanski, who was not part of the Fred Hutchinson study.
As for why exercise might be better in morning, Stepanski also suspects a change in circadian rhythm. Finding out whether morning exercise benefits the body clock would be an interesting follow-up study, he said.
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