RESEARCH SHOWS EXERCISE KEY TO GOOD NIGHT'S SLEEP.

Byline: The Boston Globe

If one of your fondest wishes is to sleep better, researchers from Stanford University School of Medicine may have just the answer: Exercise.

It's been a matter of common sense for eons that a physical workout during the day can enhance sleep at night. But until now, that's been one of those gems of folk wisdom that are long on logic and short on proof.

In today's Journal of the American Medical Association, epidemiologist Abby C. King and her team report that regular aerobic exercise four times a week dramatically improves sleep, though it is not a quick fix. It seems to take 16 weeks for the beneficial effects of exercise to fully kick in.

Although there are various speculations, it is still not clear exactly why sleep comes more easily - and lasts longer - for those who regularly have a good, brisk walk or workout.

Insomnia is an occasional problem for as many as half of all American adults, other research suggests, and a chronic problem for at least one in six.

``This is one of the best studies I've seen in terms of thorough documentation of exercise and the effect it has on sleep,'' commented psychologist Gregg Jacobs, director of the behavioral medicine insomnia program at Beth Israel Deaconess Medical Center. ``This is one more solid piece of evidence demonstrating that sleeping pills are not the solution and that behavioral techniques clearly work.''

In the study, 43 adult volunteers age 50 to 76, all of them sedentary and troubled by moderate sleep problems, were randomly assigned to one of two groups. One group was asked to exercise for 30 to 40 minutes four times a week. The other group was asked to stick to its sedentary ways.

Both groups were given repeated questionnaires about their sleep habits and kept daily ``sleep diaries'' to rate their sleep.

On average, King's team found, people who used to take longer than 25 minutes to fall asleep were able, through exercise, to cut this transition stage by 15 minutes. By contrast, the still-sedentary participants exhibited little change in the time it took to fall asleep.

Those who took up exercise also wound up sleeping nearly an hour longer every night, while the control group showed little change. The exercisers also took shorter naps than previously and rated their nighttime sleep as significantly improved.

And though they got more sleep overall, the exercisers did not show dramatic improvement in one of the other annoying sleep problems of mid and later life: waking up during the night.

Although the researchers did not use fancy laboratory tests such as recordings of brain waves to gauge the depth and duration of sleep, they did use one relatively high-tech method to verify that the exercisers did work out on schedule, and that the controls barely stirred from the couch. About half of the exercise group and half of the controls wore portable monitors that kept track of heart rate and body movement for a three-day period at the beginning and end of the trial.

During the study, the exercisers were asked to work out twice a week in a nearby YMCA and twice a week at home. At the gym, they did low-impact aerobics; at home, they did 40 minutes of brisk walking or stationary cycling. They were also asked to do their exercise before dinner, to minimize sleep disruptions.

The Stanford researchers said that it is still unclear just why exercise promotes improvements in some aspects of sleep, though muscular relaxation, reduced anxiety or stress and ``thermal effects,'' among other factors, may be involved.