Active Voice: Physical Activity and Sleep: Itís Complicated!

By Maya Lambiase, Ph.D.

Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.

Dr. Lambiase is a Department of Veterans Affairs Women's Health Postdoctoral Fellow at the University of Pittsburgh VA. Her research focuses on the relationships among physical activity, sleep, and cardiovascular disease risk. She is a professional-in-training member of ACSM.

The following commentary reflects Dr. Lambiase's views relating to the research article which she and her colleagues authored and that appeared in the December 2013 issue of
Medicine and Science in Sports and Exerciseģ (MSSE).

Almost everyone has experienced a night or two of bad sleep in their life. Unfortunately, for many people getting too little sleep or waking up during the night, this is a common experience. Like many conditions that worsen with age, sleep is no exception. Older adults often report getting less sleep, taking longer to fall asleep, and waking up more frequently than younger individuals. Sleep problems also are highly prevalent among women across the lifespan.

While most people feel better after a good nightís sleep, accumulating scientific evidence suggests that habitual sleep problems are associated with an increased risk for chronic disease. Therefore, greater awareness and understanding of sleepís role in health is crucial for researchers and practitioners alike. Additionally, identifying effective strategies to improve sleep, especially among individuals with habitual sleep problems (e.g., older women), could have noticeable benefits for both short-term (e.g., day-to-day) functioning and long-term health.

Physical activity has long been thought to be beneficial for sleep, a notion that has been adopted by the popular media, as well as by medical professionals. The link between physical activity and sleep is supported by numerous epidemiological studies that consistently demonstrate that people who are more physically active also sleep better. However, the directionality of this relationship remains unclear. Does physical activity improve sleep? Do people who sleep better increase physical activity?

To address these questions, we examined the physical activity and sleep patterns of 144 older women who were participating in an ongoing study of healthy aging at the University of Pittsburgh. A notable feature of this study is that women wore an accelerometer on their waist and an Actiwatch sleep monitor on their wrist for a full 24-hour period for seven consecutive days while they went about their normal activities. This allowed us to objectively quantify both physical activity and sleep behaviors concurrently over an entire week in a free-living setting.

Surprisingly, we found that more physical activity during the day was not associated with better sleep that night. Conversely, on nights when women slept better, they engaged in more physical activity the following day. These findings suggest that, in the short-term, sleep may have more of an impact on physical activity than the other way around. However, multiple biological, behavioral, psychological, and environmental factors affect both sleep and physical activity. Thus, the effects of physical activity on sleep are likely more complex than originally thought.

Regardless of the scientific support for physical activityís influence on sleep, a physically active lifestyle is absolutely beneficial for many aspects of health. Therefore, regular physical activity is encouraged for all individuals. Ironically, getting a good nightís sleep may be one way to increase a personís willingness or motivation to be physically active!