A power nap is a short sleep which terminates before the occurrence of deep
sleep or slow-wave sleep, intended to quickly revitalize the subject.
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.
Scientific experiments 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. Mitsuo Hayashi and Tadao Hori have demonstrated that a nap improves
mental performance even after a full night's sleep.
Power naps of less than 30 minutes—even those as brief as 6 and 10
minutes—restore wakefulness and promote performance and learning.
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