Why do I feel more tired after going back to sleep?

[iggybaseball]

I've noticed that I often wake about an hour or two before I should get up. When I awake, I often feel pretty energetic but I go back to sleep because of course, I have a couple more hours awaiting me. Then when I wake up the second time, I can feel "dead" or really tired. Does anyone know why this occurs? Does this happen to anyone else? And often when I wake up early, I haven't gotten enough sleep (for example, 5 hours) so I don't think it's an issue of oversleeping. Well thanks.

 

[fargoth]

yeah, I know this effect very well
it happens to everyone, the explanation is: sleeping cycles.
when you wake-up naturally its in the end of a cycle, but when the alarm-clock is waking you up it could be in the stage of deep sleep, and then you get up really tired.
http://www.helpguide.org/life/sleeping.htm

 

[Mk]

You could program a stun gun to wake you up the second time, then you wouldn't have to worry about being dead tired.