Simply speaking ,rem sleep is "physical sleep"

The sum of rem sleeping hour is about one hour and half.

Because brain work lively, muscle is convulsed and eyes often move.

「Is it true?」But please look at this graf. And you should check "The leg cramped up and he awoke. " Even now at this time, I remember it, seeing the dream.

"-- that -- surely -- the dream of a university entrance examination ... so .. the bulletin board of announcements of test results ... " --

Then, the leg cramped up and it awoke. placing such a thing!! lastly, I think that it is somehow true but certain to remember a muscular spasm and dream.

To『 Relation between sleep and a life 』