Napping after a lunch meal is refreshing and provides an energy boost for the second half of the day.
For inhabitants of hot countries, the siesta has been sacred for centuries.
Power naps - a short sleep taken during the working day aimed at improving the quality of work later in the day - are common in homes and offices in the United States and Asia.
And then there's the midday nap - a short moment of rest - which is a therapeutically beneficial break in a busy day.
"It's important that body and soul relax via an all-system shutdown and relief from stress factors," said Goeran Hajak, chief physician at the Department of Psychiatry, Psychosomatic Medicine and Psychotherapy in the Bamberg Social Foundation's Michelsberg Hospital in Germany.
Sleep calms a stressed nervous system.
"This means the heart beats more slowly, the breathing rate is lower, blood pressure drops and so does body temperature," said Professor of internal medicine Michael Stimpel, at Cologne University.
Stress reduction is the most obvious effect of a nap. The napper feels fit and productive again; reaction times and the ability to concentrate are improved.
"Furthermore, afternoon naps benefit overall health," said Heidrun Holstein, a physician with the Karlsruhe branch of the consumer advice centre in the German state of Baden-Wuerttemberg.
Citing a study done in 2007 by scientists from Athens and Boston, Holstein said people who took regular naps had a significantly lower risk of dying of cardiovascular diseases.
Afternoon naps are inherent in the body's basic program.
"Our bodies function in a biphasic activity-rest rhythm," said Hajak, whose areas of specialisation include somnology.
Humans have two rest phases: one at night and the other after lunch or at lunchtime.
While doctors speak of postprandial somnolence - the drowsiness following a meal that is colloquially known as a "food coma" - lunch is not the cause of the lethargy that people typically experience around noon.
The intake of food does, however, intensify the feeling of heaviness.
"The more - and the more nutritiously - that you eat at midday, the more tired you become," Stimpel said.
"The stomach needs a particularly large amount of blood for digestion. At the same time, the heart and body have to be supplied with energy, [on top of which often come the demands of a job].
"This multiple strain is the cause of the tiredness."
Power nappers should prepare a restful environment for themselves.
The perfect place for an afternoon nap is a darkened room with a comfortable daybed, Stimpel said.
Even if this isn't available, workers can easily create the right resting conditions at the workplace.
"The mobile phone can be switched off, the telephone redirected to a co-worker and the door closed - preferably with a 'Please Do Not Disturb' sign attached," Stimpel said.
Workers preparing for a nap are at the same time switching off their "attention" mode, according to Holstein, who said this was an important precondition for calming down.
Waking up at the right time is just as important as calming down, however.
"Fifteen to 30 minutes at most is ideal," Hajak said.
If the afternoon nap lasts longer, there's a danger of sleeping deeply and upsetting the body's diurnal rhythm, he warned.Hajak said it was hard for workers who took a long afternoon nap to activate their bodies again. They not only felt listless, but they also found it more difficult to calm down in the evening.
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