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.
Brief naps (10–15 minutes) can improve alertness directly after awakening without the detrimental effects of sleep inertia associated with longer naps.
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.
Power naps of fewer than 30 minutes - even those as brief as 6 and 10 minutes - can restore wakefulness and promote performance and learning. A 30-minute nap may also be able to reverse the hormonal impact of a night of poor sleep or reverse the damage of sleep deprivation. At University of Düsseldorf study found superior memory recall, once a person had reached 6 minutes of sleep, suggesting that the onset of sleep may initiate active memory processes of consolidation which - once triggered - remains effective even if sleep is terminated.
A Flinders University study of individuals restricted to only five hours of sleep per night found a 10-minute nap was overall the most recuperative nap duration of various nap lengths they examined (lengths of 5 min, 10 min, 20 min, and 30 minutes.
The 10-minute nap produced immediate improvements in all outcome measures (including sleep latency, subjective sleepiness, fatigue, vigor, and cognitive performance), with some of these benefits maintained for as long as 155 minutes;
The 20-minute nap was associated with improvements emerging 35 minutes after napping and lasting up to 125 minutes after napping.