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Is A Single Bout Of Exercise Helpful Or Harmful In Getting A Good Night’s Sleep?

Washington, DC – Most weight loss experts advocate a sensible diet and regular exercise to shed unwanted pounds. Americans are accepting that advice: low-fat meals are the staples of many diets and both sexes are now engaged in an exercise regimen. As evidence of the latter, marketing experts claim that membership growth in health and fitness club facilities will soon outpace capacity, with almost 12 percent of the population belonging to health clubs in 2000. This figure is expected to reach 41.1 million members, or 14 percent of the population, in 2006.    

Previous research has demonstrated that, in general, quality of sleep improves after regular physical exercise.  However, a number of factors such as the particular exercise training routines and various individual subjective characteristics complicate this overall conclusion. Army researchers set out to quantify the quality and length of sleep obtained after non-habitual acute resistance and aerobic exercise. Of interest was whether a single workout would be beneficial or harmful in obtaining restful sleep the night following the exercise. 

A New Study

The authors of “Non-Habitual Acute Resistance and Aerobic Exercise Affects Sleep” are William J. Tharion, Philip J. Niro, Marilyn A. Sharp, Mark D. Kellogg, Kevin R. Rarick, and Bradley C. Nindl, all at the U.S. Army Research Institute of Environmental Medicine, Natick, MA. They will present their findings at the American Physiological Society’s (APS) (www.the-aps.org) annual scientific conference, Experimental Biology 2003, being held April 17-21, 2004, at the Washington, D.C. Convention Center.

Methodology

Seven men volunteered to participate in the study.  Volunteers were physically active (i.e., they participated in recreational sports or their jobs required some physical labor), but they were not engaged in a regular training program.  The volunteer’s characteristics (all values throughout are means + standard deviations) were as follows:

Subjective measures of sleep were determined using the Pittsburgh Sleep Diary the two nights before the exercise bout and the night after the exercise bout.  An objective measure of sleep was obtained by using a wrist-worn actigraph and applying a sleep algorithm to the activity records.  The actigraph is composed of a piezoelectric sensor that measures body motion.

The exercise took place at approximately 3:00 PM and lasted up to two hours, depending on the type of exercise performed.  A repeated-measures design, with five treatment conditions, was administered.  Treatments were counter-balanced across volunteers to control for order effects.  A minimum of 30 days rest and recovery was allowed before a subsequent test session was administered.  The exercise conditions were as follows:

(1)   Resistance Exercise: Upper Body (Bench Press and Lat Pull-Downs) and Lower Body: Squat and Leg Press, with 90-seconds rest between each set.  This included High Resistance (50 5-10 RM total sets  (1 RM = the greatest amount of weight you can lift one time during a specific exercise)) and Moderate Resistance (25 five 5-10 RM total sets).

(2)   Aerobic Exercise: Consisting of High Aerobic (Six 15-min Cycling Bouts at approximately 70 percent VO₂ max) and  Moderate Aerobic  (Three 15-minute Cycling Bouts at approximately 70 percent VO₂ max) where VO₂  is peak oxygen intake.

(3)   No Exercise.

Results 

No differences existed for any of the 13 actigraph sleep measures (e.g., percent of time slept, sleep latency, times awakened from sleep, etc). A trend did exist, with 85 percent of the various actigraph sleep measures being poorer under the various exercise conditions (i.e., high and moderate volume resistance and aerobic exercise) when compared to the no exercise condition.  Volunteers also reported waking up significantly more times at night after exercise (regardless of the type of exercise) compared to before the exercise condition. 

Conclusions 

Exercise that is non-habitual produced less restful sleep regardless of exercise type.  While sleep measured by actigraphy was not significantly affected by exercise, a consistent trend showed that sleep was more disrupted after non-habitual exercise, regardless of type, compared to no exercise. After the High Volume Resistance exercise bout, volunteers reported lying awake before falling asleep longer than under all other conditions.

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The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 11,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

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Editor’s Note: For further information or to schedule an interview with a member of the research team, please contact Donna Krupa at 703.967.2751 (cell), 703.527.7357 (office) or  at djkrupa1@aol.com. Or contact the APS newsroom at 202.249.4009 between 9:00 AM and 6:00 PM EDT April 17-21, 2004.