Sleep and exercise have a bidirectional relationship (as does sleep and pain). Quality sleep promotes better physical performance, and regular exercise improves sleep quality. Numerous studies confirm that both aerobic and resistance training enhance sleep quality by reducing sleep onset latency and increasing slow-wave sleep. A meta-analysis by Kredlow et al. 2015found that regular exercise has small beneficial effects on total sleep time, small to medium beneficial effects on sleep onset latency (the time it takes to fall asleep), and moderate beneficial effects on sleep quality.
El-Kader and Al-Jiffri (2020) noted in their study of 80 sedentary individuals with primary insomnia that, after completing a six-month aerobic training program, there were significant improvements in total sleep duration, sleep efficiency, and sleep onset latency.
In their 2023 SR, authors Alnawwar et al. identified an increase in melatonin, stress reduction, body temperature regulation, and initiation of a positive feedback loop, as well as mood improvements, as mechanisms by which exercise improves sleep.
Conversely, inadequate sleep impairs exercise recovery, reduces endurance, and increases the risk of injury. For athletes and physically active individuals, insufficient sleep may also negatively affect immune function and delay tissue repair. A study by Fullagar et al. 2015 concluded that optimal athletic performance is closely tied to sufficient, high-quality sleep.
Importantly, the timing of exercise matters. High-intensity workouts late at night can elevate core temperature and delay the onset of melatonin, making it more difficult to initiate sleep. However, morning or early evening workouts tend to support healthier circadian alignment and are essential as part of the daily circadian reset.
In summary, exercise and sleep form a mutually supportive feedback loop. To maximise the benefits of both, individuals should aim for regular, moderate physical activity and prioritise consistent, sufficient sleep. Optimising this relationship between sleep and exercise enhances not only physical performance but also emotional regulation and cognitive resilience.