Well, something similar has happened to me on occasion and to several others who've told me of it once in a while. I'd guess it has to do with the dream 'disconnect' circuit keeping your body from moving as you would IN the dream. That disconnect (and the associated kinesthetic side-effects) doesn't always let go evenly and restart everything cleanly. A bad ~restart could handily lead to all of your symptoms, including the strained muscle (as a command that didn't get through gets ~auto-resent with higher amplitude just Before the successful start up). At least, that's been my working hypothesis for quite a while now. It also potentially explains why it can be so hard to break out of dreams even when you're pretty sure you're in one.
(no subject)