90 minutes is an average value. The number isn't the same for everyone and can be 80 min for one person and 100 min for the next.
Quote:
|
if you set it 90 minutes before you need to get up, since you immediately fall back asleep after turning off the alarm, won't you be completely refreshed if awakened 90 minutes later?
|
The alarm probably won't totally awake you and there will be still some of the factor that regulate the sleep phase in effect when you go to sleep again.
Quote:
|
It is very hard if even possible to wake up at the end of the cycle as they are continuous throughout the night
|
There are a few techniques that allow the detection of sleep phases and I have heard of alarm clocks that monitor your breathing pattern to find out when you can be awaken the best.
Additionally as long as you wake up during the first sleep phase of a cycle you are fine.
There are also people who naturally awake after sleep phases but go right back to sleep without having memories about the phases in between.