How exercise resets your body clock and improves sleep patterns

Exercise improves sleep quality and helps treat sleep disorders by regulating circadian rhythms, reducing stress, and enhancing physiological functions like melatonin production and autonomic balance.

Review: The impact of exercise on sleep and sleep disorders. Image Credit: Lysenko Andrii / Shutterstock

In a recent review article published in the journal npj Biological Timing and Sleep, researchers summarized the research on how exercise, or structured physical activity, improves sleep quality, both for those with sleep disorders and healthy individuals. They highlighted that the effects of exercise on sleep are influenced by factors such as an individual’s age, sex, fitness level, and the type, timing, and intensity of exercise.

Types of Exercise

Exercise is any form of repetitive, planned, and structured physical activity. Aerobic exercise involves activities that use the body’s large muscle groups, increasing the heart rate and the amount of oxygen a person uses. Swimming, cycling, and walking are forms of aerobic exercise.

While aerobic exercise improves cardiovascular health, anaerobic exercise, which includes sprinting and weight training, builds muscle strength and mass. Meanwhile, stretching exercises focus on improving an individual’s range of motion, but the evidence is mixed regarding whether or not they can prevent injuries.

Dynamic exercise involves moving joints and appears to have health benefits in the long term, including improved blood flow and lower blood pressure. However, static exercise occurs when muscles are activated without movement and can increase blood pressure significantly but build strength over time. The journal article also noted that these different forms of exercise may have distinct effects on sleep, with aerobic exercise generally providing the most benefits for sleep quality.

Advantages of Exercise

Exercise is critical to regulating weight, as it prevents excessive gain and can support weight loss by burning calories and balancing calorie expenditure and intake. It decreases the risk of diabetes, hypertension, and depression. Regular exercise also improves cardiovascular health, improves heart recovery, and decreases the resting heart rate.

Beyond physical benefits, exercise also improves mood and energy. It increases energy levels by improving the delivery of nutrients and oxygen to the tissues. Meanwhile, exercise improves mood, reduces stress, and enhances relaxation, particularly if it takes the form of activities that a person enjoys. Research has shown that exercise can reduce levels of cortisol, a stress hormone linked to sleep disturbances, while increasing melatonin, the hormone that regulates sleep cycles.

Not getting adequate amounts of exercise has been linked to chronic illnesses such as diabetes, cancer, and heart disease, which have become leading causes of global mortality.

How Exercise Improves Sleep

In healthy individuals, exercise improves sleep efficiency, which is defined as the ratio of time a person spends sleeping to the total time they spend in bed.

Specifically, exercise between four and eight hours before going to bed can reduce wakefulness during sleep and help people fall asleep faster. However, the review emphasized that exercising less than four hours before bedtime may delay melatonin release and increase body temperature, potentially making it harder to fall asleep. Regular exercise also improves overall sleep quality and helps people sleep longer.

Over time, exercise improves sleep hygiene, namely the habits that help people sleep well. This leads to stable sleep-wake cycles and improves the regulation of the body’s circadian rhythms. Because exercise acts as a “zeitgeber” (a factor that influences the body’s biological clock), it can help reset disrupted circadian rhythms, particularly in individuals who experience sleep disturbances due to shift work or jet lag.

Exercise can also indirectly improve sleep by reducing stress and enhancing mood. Regular and consistent exercise reduces stress, depression, and anxiety. By reducing the heart rate, exercise calms the body, facilitating sleep. It also regulates hormones like cortisol and melatonin, which are linked to sleep patterns.

Treating Sleep-Related Disorders

Researchers have studied the benefits of exercise for alleviating sleep disorders. Exercise has psychological benefits, reducing the emotional stress and anxiety associated with disordered sleep. It can also reduce sleep-disordered breathing and improve autonomic and hormonal imbalances that worsen sleep quality.

Regarding specific sleep disorders, people experiencing insomnia can benefit from moderate-intensity aerobic exercise, which improves the onset of sleep, reduces the time spent awake, and enhances the overall sleep quality. The review also noted that exercise may be more effective when combined with sleep hygiene interventions, such as maintaining a consistent bedtime and avoiding stimulants before sleep.

Another condition that can hamper sleep quality is restless leg syndrome (RLS), a neurological condition that causes an uncontrollable urge to move the legs. Aerobic exercise can also reduce symptoms of RLS, including throbbing, aching, and itching in the legs. The study highlighted that the benefits of exercise for RLS may be due to improved blood circulation and neuromuscular function.

For people with sleep apnea, which causes breathing to stop and start repeatedly during sleep, researchers recommend combining weight loss with exercise to reduce the severity of the condition and improve functioning and wakefulness during the day. Importantly, the review found that even in the absence of significant weight loss, regular exercise can improve sleep apnea symptoms by enhancing autonomic nervous system regulation and reducing inflammation.

Conclusions

While existing studies on the relationship between exercise and sleep are promising, researchers identified ways to apply these findings and avenues for future investigations.

Long-term studies are needed to understand how different durations, intensities, and types of exercise impact sleep patterns. Diverse populations should be included to identify tailored and effective interventions for different demographic groups. The review also called for more research into the molecular mechanisms underlying the effects of exercise on sleep, such as its impact on brain function and immune responses.

There is still much that is not known about the physiological mechanisms that underpin exercise’s impacts on sleep quality and circadian rhythms, particularly among those with chronic sleep disorders. The systemic and molecular effects of exercise on sleep also need more exploration.

Current research can be applied to interventions to improve the health of athletes and the general public. For athletes, optimizing sleep is crucial for recovery and performance, and the review suggested integrating personalized sleep-monitoring protocols into training programs.

Physical activity should be promoted as a non-pharmacological intervention for the general public, but clear guidelines regarding intensity, frequency, and timing should be provided for different age groups. The researchers stressed the importance of personalized exercise prescriptions that account for an individual’s age, fitness level, and existing sleep disturbances to maximize benefits.