A cloth with a nap.

Primarily, nap is the raised (fuzzy) surface on certain kinds of cloth, such as velvet. Nap can refer additionally to other surfaces that look like the surface of a napped cloth, such as the surface of a felt or beaver hat.

Starting around the 14th century, the word referred originally to the roughness of woven cloth before it was sheared.^[1][2] When cloth, especially woollen cloth, is woven, the surface of the cloth is not smooth, and this roughness is the nap. Generally the cloth is then 'sheared' to create an even surface, and the nap is thus removed.

Piled nap[link]

Since the 15th century, the term nap generally refers to a special pile given to the cloth.^[2] The term pile refers to raised fibres that are there on purpose, rather than as a by product of producing the cloth.^[3] In this case, the nap is woven into the cloth, often by weaving loops into the fabric, which can then be cut or left intact. Carpets, rugs, velvet, velour, and velveteen, are made by interlacing a secondary yarn through woven cloth, creating a nap or pile.

Raising the nap[link]

In the finishing process of manufacturing textiles, after the cloth is woven, it goes through processes such as washing, fulling, raising the nap, and trimming the nap. After the nap is trimmed, the fabric is considered finished. The raising process, which draws out the ends of the fibres, is done on both woollen and cotton fabric.^[4] Flannelette is a cotton fabric that goes through this process. There are ways to 'raise the nap', most of which involve wire brushes such as raising cards. Originally, dried teasel pods were used^[5] and were still preferred for use on woollen cloth for a long time.^[4] Woollen fabrics, which must be damp when raising the nap, are then dried and stretched before the nap is trimmed or sheared. Cotton cloth goes straight to the shearing process, where the nap gets trimmed to ensure that all the raised fibres are the same length.^[4]

See also[link]

• Sueding textile fabrics

References[link]

v t e Fabric Woven Aertex Airdura Airguard Barathea Barkcloth Batiste Bedford cord Bengaline silk Beta cloth Bombazine Brilliantine Broadcloth Buckram Bunting Burlap C change Calico Cambric Canvas Chambray Capilene Cedar bark Char cloth Charmeuse Charvet Cheesecloth Chiffon Chino Chintz Cloqué Cloth of gold Cordura Duck Coutil Crape Cretonne Dazzle Denim Dimity Donegal tweed Dowlas Drill Drugget Foulard Flannel Gabardine Gauze Gazar Georgette Ghalamkar Gingham Grenadine Grenfell Cloth Grosgrain Habutai Haircloth Harris Tweed Herringbone Himroo Hodden Irish linen Jamdani Kerseymere Khādī Khaki Khaki drill Kente cloth Lamé Lawn Linsey-woolsey Loden Longcloth Lumalive Mackinaw Madapolam Madras Moleskin Muslin Nainsook Nankeen Ninon Oilskin Organdy Organza Osnaburg Ottoman Oxford Paduasoy Percale Pongee Poplin Rakematiz Rayadillo Rep Rinzu Ripstop Ripstop nylon Russell cord Saga Nishiki Samite Sateen Satin Saye Scarlet Seersucker Serge Scrim Shot silk Stuff Taffeta Tais Toile Tucuyo Tweed Twill Ultrasuede Ventile Vinyl coated polyester Viyella Voile Wadmal Wigan Whipcord Zephyr Zorbeez Figured woven Brocade Camlet Damask Lampas Songket Pile woven Baize Chenille Corduroy Crimplene Fustian Mockado Moquette Plush Polar fleece Terrycloth Velours du Kasaï Velvet Velveteen Zibeline Nonwoven Felt Cedar bark Knitted Boiled wool Coolmax Machine knitting Milliskin Jersey Velour Netted Bobbinet Carbon fiber Fishnet Lace Mesh Needlerun Net Ninon Tulle Technical Ballistic nylon Ban-Lon Conductive Darlexx E-textiles Gannex Gore-Tex Silnylon Spandex Stub-tex SympaTex Windstopper Patterns Argyle Bizarre silk Herringbone Houndstooth Paisley Pin stripes Tartan (Plaid) Tattersall Textile fibers Acrylic Alpaca Angora Cashmere Coir Cotton Hemp Jute Kevlar Linen Mohair Nylon Microfiber Olefin Pashmina Polyester Piña Ramie Rayon Sea silk Silk Sisal Spandex Spider silk Wool Finishing and printing Androsia Batik Beetling Bingata Bògòlanfini Calendering Decatising Finishing Fulling Heatsetting Mercerization Moire Nap Rogan printing Rōketsuzome Roller printing Sanforization Tenterhook Textile printing Waxed cotton Woodblock printing Indienne Related Dyeing Fiber History of textiles History of silk Knitting Pandy Shrinkage Synthetic fabric Terminology Manufacturing Preservation Weaving Yarn

It has been suggested that Power nap be merged into this article or section. (Discuss) Proposed since November 2010.

Hammock napping on a patio, in Costa Rica

A nap is a short period of sleep, typically taken during daylight hours as an adjunct to the usual nocturnal sleep period. Naps are most often taken as a response to drowsiness during waking hours. Cultural attitudes toward napping during the work day vary; children and the elderly are often expected to nap during the day and are provided with designated periods and locations to do so, but most working adults are not and napping on the job is widely considered unacceptable. On the other hand, many cultures (especially those in hot climates) serve their largest meals at midday, with an official allowance for a nap period (siesta) afterwards before returning to work.

Negative effects[link]

Naps (even multiple per day) are not typically long or deep enough to provide the same restorative benefits as a continuous 6–8 hour period of sleep, and can result in the accumulation of a sleep deficit if naps are regularly used as a substitute. Naps are also not recommended for those suffering from insomnia or depression, as they may aggravate already disrupted rest/wake patterns.^[1]

Benefits[link]

Napping has been found to be both physiologically and psychologically beneficial. Napping for 20 minutes can help refresh the mind, improve overall alertness, boost mood and increase productivity.^[2] Napping may benefit the heart. In a six-year study of Greek adults, researchers found that men who took naps at least three times a week had a 37 percent lower risk of heart-related death.^[3] Napping may also relieve headaches. Scientists have been investigating the benefits of napping for years: the 20-minute nap, as well as sleep durations of 1–2 hours. Performance across a wide range of cognitive processes has been tested.^[4] Studies demonstrate that naps are as good as a night of sleep for some types of memory tasks. A NASA study led by David F. Dinges, professor at the University of Pennsylvania School of Medicine, found that naps can improve certain memory functions and that long naps are more effective than short ones.^[5] In that NASA study, volunteers spent several days living on one of 18 different sleep schedules, all in a laboratory setting. To measure the effectiveness of the naps, tests probing memory, alertness, response time, and other cognitive skills were used.

The National Institute of Mental Health funded a team of doctors, led by Alan Hobson, Robert Stickgold, and colleagues at Harvard University for a study which showed that a midday nap reverses information overload. Reporting in Nature Neuroscience, Sara Mednick, Stickgold and colleagues also demonstrated that, in some cases, a 1-hour nap could even boost performance to an individual's top levels. The NIMH team wrote: "The bottom line is: we should stop feeling guilty about taking that 'power nap' at work."^[6]

Cardiovascular Benefits of Napping (Siesta/Daytime sleep)[link]

The siesta habit has recently been associated with a 37% reduction in coronary mortality, possibly due to reduced cardiovascular stress mediated by daytime sleep (Naska et al., 2007). Nevertheless, epidemiological studies on the relations between cardiovascular health and siesta have led to conflicting conclusions, possibly because of poor control of moderator variables, such as physical activity. It is possible that people who take a siesta have different physical activity habits, e.g. waking earlier and scheduling more activity during the morning. Such differences in physical activity may mediate different 24-hour profiles in cardiovascular function. Even if such effects of physical activity can be discounted for explaining the relationship between siesta and cardiovascular health, it is still unknown whether it is the daytime nap itself, a supine posture or the expectancy of a nap that is the most important factor. It was recently suggested that a short nap can reduce stress and blood pressure (BP), with the main changes in BP occurring between the time of lights off and the onset of stage 1 (Zaregarizi, M. 2007 & 2012).

Dr. Zaregarizi and his team have conducted that the acute time of falling asleep was where beneficial cardiovascular changes take place. This study has indicated that a large decline in blood pressure occurs during the daytime sleep-onset period only when sleep is expected however when subjects rest in a supine position, the same reduction in blood pressure is not observed. This blood pressure reduction may be associated with the lower coronary mortality rates seen in Mediterranean and Latin American populations where siestas are common. Dr. Zaregarizi assessed cardiovascular function (blood pressure, heart rate, and measurements of blood vessel dilation) while nine healthy volunteers, 34 years of age on average, spent an hour standing quietly; reclining at rest but not sleeping; or reclining to nap. All participants were restricted to 4 hours of sleep on the night prior to each of the sleep laboratory tests. During the three phases of daytime sleep, he noted significant reductions in blood pressure and heart rate. By contrast, they did not observe changes in cardiovascular function while the participants were standing or reclining at rest. These findings also show that the greatest decline in blood pressure occurs between lights-off and onset of daytime sleep itself. During this sleep period, which lasted 9.7 minutes on average, blood pressure decreased, while blood vessel dilation increased by more than 9 percent. “There is little change in blood pressure once a subject is actually asleep," Dr. Zaregarizi noted, and he found minor changes in blood vessel dilation during sleep (Zaregarizi, M. 2007 & 2012).

Power nap[link]

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 (SWS), intended to quickly revitalize the napper. The expression "power nap" was coined by Cornell University social psychologist James Maas.^[7]

The 20-minute nap increases alertness and motor skills.^[8] Various durations may be recommended for power naps, which are very 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 more sleepy 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.

People who regularly take these short naps, or catnaps as they used to be called, may develop a good idea of the duration which works best for them, as well as which tools, environment, position, and associated factors help produce the best results. Power naps are effective even when schedules allow a full night's sleep. Mitsuo Hayashi and Tadao Hori^[9] have demonstrated that a nap improves mental performance, even after a full night's sleep.

Caffeine nap[link]

A caffeine nap is a short nap that is preceded by the intake of caffeine. In a driving simulator and a series of studies, Horne and Reyner investigated the effects of cold air, radio, a break with no nap, a nap, caffeine pill vs. placebo and a short nap preceded by caffeine on mildly sleep-deprived subjects. The latter was by far the most effective in reducing driving "incidents" and subjective sleepiness. Caffeine in coffee takes up to a half-hour to have an alerting effect, hence "a short (<15min) nap will not be compromised if it is taken immediately after the coffee."^{[10][11][12][13]}

Systematic napping as a lifestyle[link]

A contemporary fad called polyphasic sleeping entails avoiding long sleeps, instead taking regularly spaced short naps. Sara Mednick, whose sleep research investigates the effects of napping, included a chapter, "Extreme Napping", in her book Take a Nap!.^[14] In response to questions from readers about the "uberman" schedule of "polyphasic sleeping", she commented as follows:

This practice rests upon one important hypothesis that our biological rhythms are adaptable. This means that we can train our internal mechanisms not only when to sleep and wake, but also when to get hungry, have energy for exercise, perform mental activities. Inferred in this hypothesis is that we have the power to regulate our mood, metabolism, core body temperature, endocrine and stress response, basically everything inside this container of flesh we call home. Truly an Uberman feat!^[15]

Polyphasic sleep is claimed to be of particular benefit in cases where very long periods of wakefulness (+24 hours) are necessary and a normal circadian rhythm is impossible (such as certain cases of military duty or emergency service). Critics of polyphasic sleep dispute the notion that the human brain can simply be classically conditioned to tolerate a state of near constant wakefulness without deleterious effects. Studies by the US military showed the success rate of introducing polyphasic sleep varied widely depending on individual physiology/psychology, the amount of time provided to acclimate to the new schedule, and the type and difficulty of the tasks being performed. Attempting to acclimate to a polyphasic schedule often induced significant stresses in the participants, with a corresponding deficits in alertness and skill that became progressive and did not improve until the restoration of normal sleep. Many of the more radical cycles (such as Mednick's "Uberman Schedule", allowing only 15 minute naps every 4 hours) are so demanding that to date their only successes have been anecdotal reports from serious devotees and are widely considered to be harmful and physically unsustainable for the average person.

See also[link]

• Siesta

References[link]

Naska, A., Oikonomou, E., Trichopoulou, A., Psaltopoulou, T. and Trichopoulos, D. (2007). Siesta in healthy adults and coronary mortality in the general population. Archives of Internal Medicine, 167, 296-301.

MohammadReza Zaregarizi, Ben Edwards, Keith George, Yvonne Harrison, Helen Jones and Greg Atkinson. (2007). Acute changes in cardiovascular function during the onset period of daytime sleep: Comparison to lying awake and standing. American J Appl Physiol 103:1332-1338.

MohammadReza Zaregarizi (Author). Effects of Exercise & Daytime Sleep on Human Haemodynamics: With Focus on Changes in Cardiovascular Function during Daytime Sleep Onset. BOOK, ISBN (978-3-8484-1726-1), March, 2012.

External links[link]

• How to nap GIF image – Sunday Ideas section, The Boston Globe. Image source dated 2008/06/14. Accessed 2009-06-16.
• Text reprint – Napping: the expert's guide The Guardian 27 January 2009. Accessed 2009-06-16