Posted by David on May 22, 2001 at 14:49:28:
In Reply to: Ultrashort & Polyphasic Sleep Info needed posted by Craig on May 21, 2001 at 09:40:16:
There are several factors to consider when scheduling naps such as time of day, length of nap, and individual differences in sleep patterns.
In a study done by a group of researchers in Detroit, different subjects were deprived of sleep and then allowed to take naps of varying length. One of the surprising results of this study was that naps 30 and 60 minutes long did not provide the subjects with substantially more restorative sleep than naps 15 minutes long. A nap of two hours, however, allowed subjects more than double the restorative sleep of a single hour nap. This means that a worker will be better rested and better able to perform his job by scheduling a straight two hour stretch of sleep before coming to work.
The time of day is important to consider when scheduling naps. Regardless of how long someone has gone without sleep, his body continues to follow a circadian rhythm of sleep/wake cycle, making napping more difficult during certain times of the day (i.e. during circadian peaks).
A nap taken when a person is more relaxed and ready for sleep will be deeper and more restorative. At some times of day, it is very difficult to sleep no matter how tired a person feels, especially if they have had coffee or ingested other stimulants within the previous several hours.
The length of time it takes to fall asleep is also related to time of day. People on a normal daytime awake/nighttime asleep schedule fall asleep more quickly in the early morning, early afternoon, and shortly before the usual bedtime. The worst time to try to nap if an individual is accustomed to the day shift is from about 6 p.m. to just prior to the customary bedtime, due to peak circadian alertness that occurs in the early evening. These differences do become less significant, however, if an individual has been sleep deprived or working night shifts for an extended period of time.
Another important factor to consider is sleep inertia, the time it takes to return to full alertness after sleep. At certain times of day, a prolonged nap can be detrimental to performance because of the long recovery time. Relatively brief naps have minimal sleep inertia, and a person typically returns to full alertness within minutes. Similarly, awakening in the middle of the deep stages of sleep increases inertia. That is why 1-hour naps are less desirable than those of 20 minutes or 2 hours, since the person will most likely wake from Stages 1 and 2 after a 20 minute nap, whereas a person will wake from Stage 3 or 4 (the deepest sleep) after 45 minutes to 1 hour of sleep.
Hope this helps!
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