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The Relationship Between Sleep and Exercise

By: Mary K. Mulcahey, MD and Symone M. Brown, MPH

It is no secret that we live in a progressively fast-paced society. With us constantly moving from one thing to the next and balancing many responsibilities, we often find ourselves neglecting certain aspects of our lives. Typically, we are conflicted with making the decision of losing sleep to exercise or not exercising to sleep longer. Although it is common knowledge that both sleep and exercise are important, a majority of adults are not meeting the recommended daily guidelines of 7-9 hours of sleep and approximately 30 minutes of exercise. By disregarding these two factors, individuals are making themselves more susceptible to certain health conditions such as cardiovascular disease, obesity, type 2 diabetes, and depression. With this being the case, physicians and scientists have recently begun to examine the relationship between sleep and exercise and how these two factors impact overall health and well-being.

Sleep is an important aspect for superlative health. The average adult should attain anywhere between 7-9 hours of sleep, however, only one-third of American adults meet this requirement. Research demonstrates that active adults need between 9-10 hours of sleep. This increase in optimal sleep time may be related to the need to recover from exercise conducted during the day.

Contrary to popular belief, sleeping is a very detailed process. Our sleeping patterns are contingent upon the Circadian Rhythm, which serves as our body’s internal clock. A major function of the Circadian Rhythm is to send a signal to our brain to release melatonin, a chemical that makes our bodies feel “tired.” If an individual is sleep deprived, the Circadian Rhythm will not function as efficiently as it should. While we sleep, our bodies undergo an extensive series of biological processes, including restoration of the immune and muscular system and consolidation of memories. More specifically, our bodies utilize sleep to replenish the energy that was expended during the day. Sleep has multiple positive effects on the body, including improved memory, decreased inflammation, improved focus, healthier weight, and lower stress levels.

Given the impact of sleep on the overall function of the body, numerous studies have sought to understand the connection between sleep and exercise. Researchers have noted that sleep loss in athletes is associated with rapid development of exhaustion, impaired recovery time between strenuous exercise sessions, and increased risk of sustaining an injury. The direct connection between sleep and injuries is still unclear, but medical professionals believe that it is in part related to individuals experiencing fatigue at higher levels than normal and the body’s inability to fully recover. Additionally, sleep deprivation negatively affects a number of factors associated with well-being, including increased soreness, poor mood, inhibited decision making, depression, and confusion.

On the other end of the spectrum, a number of recent studies have concluded that exercise can have a positive impact on sleep including improved quality of sleep, increased sleep efficiency, and an increase in the total amount of time spent sleeping. This positive correlation has led many physicians to begin prescribing exercise as a non-pharmacologic therapy for patients who experience a variety of sleep disorders, including insomnia and sleep disordered breathing.

Ultimately, the overall effects of exercise are determined by both the exercise protocol and individual characteristics (e.g. age, fitness level, body mass index (BMI), and sex). Factors that comprise the exercise protocol include the intensity, duration, and environment of the workout (indoor vs. outdoor, cold vs. hot), time of day, and whether the workout was classified as aerobic or anaerobic. When it comes to the timing of exercise (morning or night), there is still uncertainty as to which time of day provides better benefits for sleeping. For example, one study noted that exercising in the morning can improve the quality of nocturnal sleep, while another study states that working out an hour before bedtime will also increase deep sleep. It is safe to say that any form of exercise, regardless of the time of day, will positively influence an individual’s sleep quality.

Based on the availability of current research, the underlying theme remains; exercise has a positive impact on sleep. It is important that as an active individual, you maintain a consistent sleeping routine and try to attain at least 7 hours of sleep a night. Sleep not only improves your athletic performance, but it also helps improve and maintain your overall health and well-being; leading to a healthier and happier lifestyle.

**Dr. Mulcahey is a board certified orthopaedic surgeon and the Director of the Women’s Sports Medicine Program at Tulane, which is the only program of its kind in the south. She specializes in the operative and non-operative management of knee and shoulder injuries including ACL tears, patellar instability, meniscus tears, rotator cuff tears, and shoulder instability. Dr. Mulcahey has a passion for supporting and promoting the overall health and wellness of active and athletic women.