Editing Power nap (section)

==Characteristics==
A power nap, also known as a Stage 2 nap, is a short slumber of 20 minutes or less which terminates before the occurrence of deep [[slow-wave sleep]], intended to quickly revitalize the napper. The expression "power nap" was coined by [[Cornell University]] [[social psychologist]] [[James Maas]].<ref name="Mednick">{{cite book |last=Mednick |first=Sara C. |author2=Mark Ehrman |title=Take a Nap! Change Your Life |year=2006 |edition=First |publisher=Workman Publishing |location=New York, NY, USA |isbn=978-0-7611-4290-4 |url-access=registration |url=https://archive.org/details/takenapchangeyou00medn }}</ref>

The 20-minute nap increases alertness and motor skills.<ref name="Mednick"/> Various durations may be recommended for power naps, which are short compared to regular sleep. The short duration prevents nappers from sleeping so long that they enter the slow wave portion of the normal sleep cycle without being able to complete the cycle. Entering deep, slow-wave sleep and failing to complete the normal sleep cycle, can result in a phenomenon known as [[sleep inertia]], where one feels groggy, disoriented, and even sleepier than before beginning the nap. In order to attain optimal post-nap performance, a Stage 2 nap must be limited to the beginning of a sleep cycle, specifically [[sleep stages]] N1 and N2, typically 18–25 minutes.

Experimental confirmation of the benefits of this brief nap comes from a [[Flinders University]] study in [[Australia]] in which 5, 10, 20, or 30-minute periods of sleep were given. The greatest immediate improvement in measures of alertness and cognitive performance came after the 10 minutes of sleep. The 20 and 30-minute periods of sleep showed evidence of sleep inertia immediately after the naps and improvements in alertness more than 30 minutes later, but not to a greater level than after the 10 minutes of sleep.<ref>{{cite journal |last=Brooks |first=A |author2=Lack, L. |year=2006 |url=https://www.scopus.com/record/display.url?eid=2-s2.0-33745118693&origin=inward&txGid=350283ECD84BD6A56AA7FBA2A5F7C097.53bsOu7mi7A1NSY7fPJf1g%3a1 |title=A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? |journal=Sleep |volume=29 |issue=6 |pages=831–840 |access-date=18 April 2015|doi=10.1093/sleep/29.6.831 |pmid=16796222 |doi-access=free |url-access=subscription }}</ref> Power naps are effective even when schedules allow a full night's sleep.<ref>{{cite journal |title=The effects of a 20-min nap before post-lunch dip |journal=Psychiatry and Clinical Neurosciences |volume=52 |issue=2 |pages=203–204 |date=1 April 1998 |doi=10.1111/j.1440-1819.1998.tb01031.x |pmid=9628152 |last1=Hayashi |first1=Mitsuo |last2=Hori |first2=Tadao |s2cid=14147227 }}</ref>