My HR goes up to about 80-90 as I'm preparing for a ride (I'll put my monitor on first before dressing), but it's due to the excitement and nervousness of the upcoming ride. I used to wear the monitor to bed on occasion to get a good average resting rate, but then I read somewhere that your HR actually increases slightly while you sleep (digestion and repair). I now try to take it early morning, before I eat or drink anything.