Oh, for a good night's sleep.

A common belief among many fitness enthusiasts is that regular exercise helps them sleep better. Before exploring whether this is really the case, let's examine this thing called sleep. Troubled sleep. Sleep is defined as unconsciousness from which the person can be aroused by sensory or other stimuli." In other words, it is unlike coma, "unconsciousness from which the person cannot be aroused." However, if recent data are any indication, many of us may prefer a few bouts of coma to that of insomnia, one of our most prevalent health complaints after the common cold.

According to a recent report by the National Commission on Sleep Disorders Research, as many as 80 million people have serious, incapacitating sleep problems, 20 to 40 percent have insomnia, and nearly half of older adults say they can't get a solid night's rest. The vast majority of us fail to understand what to do about poor sleep and the consequences.

Sleep loss and sleep disturbances are thought to play a major role in 200,000 to 400,000 automobile accidents each year, with as many as 13 percent of accident-related fatalities caused by falling asleep at the wheel. People with chronic insomnia have a diminished ability to concentrate, memory problems, trouble in carrying out daily tasks, and difficulty in working with and getting along with other people. The sleep cycles. A night's sleep consists of four or five cycles, each of which progresses through several stages. During the night a person alternates between slow-wave sleep, also called nonrapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep, The entire cycle of slow-wave sleep and REM takes about 90 minutes. The average adult sleeps 7.5 hours (five full cycles), with 20 percent of that in REM. By age 70, total sleep time decreases to about six hours (four sleep cycles), but the proportion of REM stays at about 20 percent.

In slow-wave sleep, brain activity, heart rate, respiration, blood pressure, and metabolism (vital signs) slow down as a deep, restful state is reached. Sleep begins with NREM, during which brain waves gradually lengthen through four distinct stages.

Stage 1--characterized by lighter sleep, a slowing down of brain activity and vital signs with dreamlike thoughts.

Stage 2--characterized by slightly deeper sleep and slower vital signs.

Stages 3 and 4 (delta level)--characterized by deep sleep, depressed vital signs, and slow, low-frequency, high-amplitude brain activity known as delta waves.

Slow-wave sleep usually terminates with the sleeper changing position. The brain waves now reverse their course as the sleeper heads for the active REM stage. The central nervous system puts on a display of physiology so intense that Dr. Frederick Snyder of the National Institute of Mental Health terms it "a third stage of earthly existence," distinct from slow-wave sleep and wakefulness.

In REM the eyes dart about under closed eyelids, and vivid dreams transpire that can often be remembered. The even breathing of NREM gives way to halting uncertainty, and the heart rhythm speeds or slows unaccountably. The brain is highly active during REM sleep, and overall brain metabolism may be increased above the level experienced when awake.

Better sleep. Getting a good night's sleep has proven to be a difficult goal for many in this modem era. Although Solomon once noted that "a lazy man sleeps soundly" Proverbs 19:15, TLB),(*) this option is avoided by most stressed-out, twentieth-century men and women.

The Better Sleep Council is recognized as one of the leading sleep educators in the U.S. and Canada, and has published several guidelines for better sleep. One of those guidelines is to exercise regularly. According to the Better Sleep Council, "exercise enhances sleep by burning off the tensions that accumulate during the day, allowing both body and mind to unwind. While the fit seem to sleep better and deeper.... you don't have to push to utter exhaustion. A 20- to 30-minute walk, jog, swim, or bicycle ride at least three days a week ... should be your goal. But don't wait too late in the day to exercise. In the evening, you should be concentrating on winding down rather than working up a sweat.... The ideal exercise time is late afternoon or early evening, when your workout can help you shift gears from daytime pressures to evening pleasures."

Do the fit sleep better? The statements by the Better Sleep Council on the value of exercise in improving the quality and quantity of sleep are unfortunately based on relatively few well-designed studies. There is considerable debate on the value of exercise in improving sleep, resulting in large part from the difficulty researchers have in measuring sleep quality.

Some sleep researchers feel that NREM sleep, especially the delta level, helps restore and revitalize people for the next day. When people initiate and maintain heavy exercise programs, it would make sense that during sleep they would have to increase the amount of delta level sleep to compensate. In other words, if there is an increase in energy expenditure through exercise, this requires more restoration time in the form of more sleep overall, especially delta level.

Several studies have indeed shown that physically fit individuals do spend a greater proportion of their sleep hours in the delta level and tend to sleep longer overall. For example, in one study of 12 aerobically fit and 12 sedentary older men, fit subjects were found to spend more time in delta level sleep and also went to sleep faster, had less time awake during sleeping hours, and experienced an overall higher sleep efficiency. In this same study, high body heat leading to sweating from one exercise bout close to bedtime was found to have an adverse effect on sleep quality for both fit and sedentary subjects. This provides support for the recommendation to avoid heavy exercise late in the day.

Very few exercise training studies have been done to determine if initiating and maintaining an exercise program improves sleep quality. In one study of eight new many recruits, 18 weeks of basic training were found to improve sleep quality by several measures. However, most of the sleep quality improvements occurred within the first nine weeks of training, when the recruits were adapting to the increased exercise. Further research is needed to see if good sleep quality accompanies regular exercise.

Seeking help. According to the Better Sleep Council, "Sleep problems have become a modem epidemic that is taking an enormous toll on our bodies and minds. Desperately trying to fit more into the hours of the day, many people are stealing extra hours from the night." Yet even those who want to sleep more often can't because the stress of the day wreaks havoc on the brain during the night. If exercise doesn't seem to be working for you and you need additional help to get a good night's sleep, contact:

The American Sleep Disorders Association 604 Second Street SW. Rochester, Minnesota 55902

National Sleep Foundation 122 South Robertson Blvd. Suite 201 Los Angeles, California 90048

(*) Verses marked TLB are taken from The Living Bible, copyright @ 1971 by Tyndale House Publishers, Wheaton, Ill. Used by permission.

David C Nieman, Dr.P.H., F.A.C.S.M. teaches in the Department of Health, Leisure, and Exercise Science at Appalachian State University, Boone, North Carolina.