Quote:
Originally Posted by ahimel  Most people have a sleep cycle of around 90 minutes, meaning that if you get less than 90 minutes sleep, you'll be tired and groggy. After my polyphasic experiment, I found that if left to my own devices, I would sleep for 52 minutes and then wake up. |
In both my research and my personal experience, I have found the 90 minute cycle to hold true. It's especially obvious if I take an afternoon nap without setting a time limit: I'll wake up exactly 1.5 hours later. However, I did meet a person who says he naps every afternoon for ~45 minutes, and that's perfect for him.
Perhaps some people just have a really short cycle, or perhaps it's really not a complete cycle after all.
This article outlines various types of naps including the "Lazy Man's Nap" from 50-90 minutes. "You must keep the nap to 20 minutes or slightly less, and if you need the extra sleep, wait until the 50-minute mark."