Workout Does Not Contribute To Better Sleep

By Margarita Nahapetyan

Individuals who think that a good day's workout will give them a good night's sleep, appear to be wrong, if the latest research is to be believed. According to new findings, by making you more tired, a good exercise will keep you awake, rather than send you off.

The findings are based on an analysis of an experiment that involved 14 adult individuals. All the participants were asked to wear actigraphy armbands that measure body temperature as well as ambient temperature, position sense, and accelerometry for approximately 23 days. The experts also gathered information about total sleep time of the subjects, their sleep efficiency, total energy expenditure, exercise energy expenditure, non-exercise activity steps and Body Mass Index (BMI). When split by BMI, half of the participants were within a normal BMI range (under 25 kg/m2) and the other half were overweight (over 25 kg/m2).

To their surprise, the investigators came up with some interesting results. They found that the participants who had higher BMI, expended more energy, compared to their counterparts with normal weight. In addition, lower activity days meant an average of 42 minutes extra sleep time during those nights. In other words, the study revealed that days with increased activity were followed by nights with lower total sleep time (TST), whereas nights with lower TST were followed by increased activities during the next day.

The principal author of the study, Dr. Arn Eliasson, from the Integrative Cardiac Health Project at Walter Reed Army Medical Center in Washington, DC, said that the results of the study were quite the opposite of what his team had expected. "It has long been recommended, even championed, that physical activity is part of the recipe for improved sleep. Our data do not support that notion," Dr. Eliasson said.

The longest sleep and best sleep efficiency was observed after days with low non-exercise exertion, Dr. Eliasson said. Similarly, the experts expected that participants who had better rest would be more willing to workout or have busier days. However, better rested individuals turned out to get less exercise and had less calorie expenditure. After more or less normal sleep, more than six hours, all measures of exertion significantly dropped.

Dr. Eliasson assumes that the new findings may be explained by types of personality: people who are Type A, i.e. ambitious, active people throughout the day, may also be more hyper-active at nighttime and therefore, sleep less hours, while individuals who are Type B - lower-key people who are not very active - may have no problem falling or staying asleep. Another possible explanation could be that stress associated with work and life, in general, is linked to busier days, more exertion and more calories burned, but may cause difficulties with sleep.

It has always been thought that physical activity improves sleep because it causes a rise in body temperature, which is then being dropped after a while. It is exactly this decrease in temperature that apparently makes people feel tired and sleepy. So the traditional advice has been to workout at least three to fours before going to bed in order to give body time to cool down and avoid having a hard time falling asleep. But now scientists may have to re-consider their beliefs and start thinking all over again.

The findings were presented June 8, at SLEEP 2009, the 23rd Annual Meeting of the Associated Professional Sleep Societies.