Power nap
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A power nap (sometimes called a catnap) is a short nap, usually 15-20 minutes, coined by Cornell University social psychologist James Maas. It is thought by many to maximize the benefits of sleep versus time. This type of sleep pattern may be associated with polyphasic sleep; however, it is more often used to supplement normal sleep, especially when the sleeper has accumulated a sleep deficit.
Advocates of this sleep pattern recommend various durations for a power nap. Many have a precise time which they say is optimal—usually around 20-35 minutes. People who regularly take power naps usually have a good idea of what duration works best for them. Some people take power naps out of necessity. For example, someone who doesn't get enough sleep at night and is drowsy at work may sleep during his or her lunch break. Others may prefer to regularly take power naps even if their schedule allows a full night's sleep. Importantly, napping skills are trainable and have been shown to become more efficient in more experienced nappers.
The short duration of a power nap prevents nappers from entering Slow-wave sleep. Waking up after a person has entered this deeper state of sleep can result in a phenomenon known as sleep inertia, perhaps causing the person to feel groggy. Research has shown, however, that splashing water on one's face, brief exercise or a shot of caffeine can help decrease the ill effects of sleep inertia.
While a power nap and a catnap can be considered to be synonymous in terms of duration and effect, the vernacular usage often makes a behavioral distinction where a power nap involves a break from activity, while a catnap is of a more leisurely nature. Thus, one may take a power nap in the middle of a busy work day, and a catnap on the couch during a lazy afternoon, but not vice versa.
Scientists have recently begun investigating the benefits of napping for performance across a wide range of cognitive processes. Since these seminal studies demonstrated that naps were as good as a night of sleep on some memory tasks, more sleep laboratories have reported similar results. A NASA study has found, however, that while naps improve memory functions, they do not aid basic alertness.[1]
Some people report adverse physical and psychological affects to napping, including heartburn, headache, soreness of muscles, and psychologically, a profound inexplicable depression, feelings of loneliness or deep fear, a sense of pointlessness, and a feeling that an inordinate amount of time has passed. Most people who experience this report that the sensations last through the rest of the day.
In the Australian state of Victoria, the Transport Accident Commission has invested in advertising campaigns, advising drivers to take a "15 minute powernap" to help reduce the risk of fatigue when operating a motor vehicle. Some commercial enterprises are also catering to customers by offering "power nap solutions":
