Regular physical activity is frequently recommended as a path to improving sleep. There is evidence suggesting that sleep and physical activity have a bi-directionally beneficial relationship. Some studies have found that regular exercise can lead to improvements in subjective sleep quality improves, longer total sleep time and more intense deep sleep. Patients with sleep disorders such as insomnia or obstructive sleep apnea are often advised to begin an exercise regimen to improve sleep.
However, the experimental evidence supporting the relationship between exercise and sleep appears to be less clear cut than many people believe. The evidence is strong that sleep can impact performance, particularly that sleep deprivation can have a negative impact on performance in next day exercise , leading to lower intensity and duration of exercise. It is not clear though that exercise leads directly to better sleep.
Epidemiological studies indicate that sleep and exercise are correlated. But the causal relationship is unclear. People who exercise more report sleeping better, while non-exercisers are more likely to be sleep deprived and suffer from sleep apnea . It may take several weeks or months of continued exercise for a significant improvement in sleep to occur. A healthy lifestyle that includes regular exercise is more likely to lead to better sleep than a sedentary lifestyle.
Exercise directly before going to bed can interfere with sleep. Exercise can raise core body temperature for over an hour, making it difficult to initiate sleep which requires a drop in core body temperature. To avoid this effect, it is better to exercise at least 2-3 hours before bedtime.