Characteristics
The power nap is thought to maximize the benefits of sleep versus time. It is used to supplement normal sleep, especially when a sleeper has accumulated a sleep deficit.
Various durations are recommended for power naps, which are very short compared to regular sleep. The short duration of a power nap is designed to prevent nappers from sleeping so long that they enter a normal sleep cycle without being able to complete it. Going beyond sleep stages I and II but failing to complete a full sleep cycle, can result in a phenomenon known as sleep inertia, where one feels groggy, disoriented, and even more sleepy than before beginning the nap. Brief naps (10–15 minutes) can improve alertness directly after awakening without the detrimental effects of sleep inertia associated with longer naps.
Scientific experiments (see Benefits section below) and anecdotal evidence suggest that an average power nap duration of around 30 minutes is most effective. Any more time, and the body enters into its usual sleep cycle. People who regularly take power naps may develop a good idea of what duration works best for them, as well as what tools, environment, position, and associated factors help induce the best results. Others may prefer to take power naps regularly even if their schedules allow a full night's sleep. Mitsuo Hayashi, PhD and Tadao Hori, PhD have demonstrated that a nap improves mental performance even after a full night's sleep. New sleep sensors and sleep timers available on several mobile devices allow advocates of power naps to sleep for exactly as long as they would like to.
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