(_ _ z) - power nap 101.

You all know how I love taking naps during class and breaks, well here is something that might help you understand this habit of mine.

Here's how the power nap works: Sleep comes in five stages that recur cyclically throughout a typical night, and a power nap seeks to include just the first two of them. The initial stage features the sinking into sleep as electrical brain activity, eye and jaw-muscle movement, and respiration slow. The second is a light but restful sleep in which the body gets ready -- lowering temperature, relaxing muscles further -- for the entry into the deep and dreamless "slow-wave sleep," or SWS, that occurs in stages three and four. Stage five, of course, is REM, when the eyes twitch and dreaming becomes intense.

The five stages repeat every 90 to 120 minutes. Stage one can last up to 10 minutes, stage two until the 20th minute. Extenuating circumstances, like manning the controls of a jet, aside, experts believe that the optimal power nap should roughly coincide with the first 20 minutes in order to give you full access to stage two's restorative benefits. In addition to generally improving alertness and stamina, stage two is marked by a certain electrical signals in the nervous system that seem to solidify the connection between neurons involved in muscle memory. "It's like a welding machine," says Mednick. "When you wake up, your neurons perform the same function as before, but now faster and with more accuracy," making the 20-minute nap indispensible to the hard-working athlete looking to straighten out his putter or baseline shot.

Mednick's most recent research also shows that power naps can lift productivity and mood, lower stress, and improve memory and learning. In fact, Mednick has found through MRIs of nappers that brain activity stays high throughout the day with a nap; without one, it declines as the day wears on. Tell that to the boss next time he finds you passed out at your desk.

There is, however, a pitfall in all this sleeping around. You have to carefully time the duration of your nap in order to avoid waking in slow-wave sleep. This can produce what's known as sleep inertia. That's when the limbs feel like concrete, the eyes can't focus, the speech is slurred, the mind is sluggish. Sleep inertia can ruin your day. You must keep the nap to 20 minutes or slightly less, and if you need the extra sleep, wait until the 50-minute mark. This will safely keep you on the power side of your nap.

Getting The Perfect Nap
Everyone, no matter how high-strung, has the capacity to nap. But the conditions need to be right. Dr. Sara Mednick, who will publish a book on napping in the spring (tentatively titled Take Back the Nap!, Workman Publishing) has some helpful hints:

1 The first consideration is psychological: Recognize that you're not being lazy; napping will make you more productive and more alert after you wake up.
2 Try to nap in the morning or just after lunch; human circadian rhythms make late afternoons a more likely time to fall into deep (slow-wave) sleep, which will leave you groggy.
3 Avoid consuming large quantities of caffeine as well as foods that are heavy in fat and sugar, which meddle with a person's ability to fall asleep.
4 Instead, in the hour or two before your nap time, eat foods high in calcium and protein, which promote sleep.
5 Find a clean, quiet place where passersby and phones won't disturb you.
6 Try to darken your nap zone, or wear an eyeshade. Darkness stimulates melatonin, the sleep- inducing hormone.
7 Remember that body temperature drops when you fall asleep. Raise the room temperature or use a blanket.
8 Once you are relaxed and in position to fall asleep, set your alarm for the desired duration (see below).

How Long Is A Good Nap?
THE NANO-NAP: 10 to 20 secondsSleep studies haven't yet concluded whether there are benefits to these brief intervals, like when you nod off on someone's shoulder on the train.
THE MICRO-NAP: two to five minutes Shown to be surprisingly effective at shedding sleepiness.
THE MINI-NAP: five to 20 minutes Increases alertness, stamina, motor learning, and motor performance.
THE ORIGINAL POWER NAP: 20 minutesIncludes the benefits of the micro and the mini, but additionally improves muscle memory and clears the brain of useless built-up information, which helps with long-term memory (remembering facts, events, and names).
THE LAZY MAN'S NAP: 50 to 90 minutesIncludes slow-wave plus REM sleep; good for improving perceptual processing; also when the system is flooded with human growth hormone, great for repairing bones and muscles.