Use this tag for questions about how sleep relates to physical fitness.
Sleep is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than being in hibernation or a coma. Sleep is a heightened anabolic state, accentuating the growth and rejuvenation of the immune, nervous, skeletal and muscular systems. It is observed in all mammals, all birds, and many reptiles, amphibians, and fish.
Factors that impact the quality of sleep are often collected under the term "sleep hygiene", see for example the National Sleep Foundations tips.
This tag is to be used for questions about physical fitness, relating to sleep. This tag is not to be used for questions about sleep as a subject, as that is off topic for this site.