Although I do have to say that when I took it in college it DID do something to my sleep (not muscles though). I would go to sleep and wake up super early and I'd be wide wide awake. I had lots of dreams too. It's kind of weird.
And it WASN'T placebo because I didn't even know it was known to mess with sleep at the time (it was right when ZMA came out and I took it for the claimed test upping effects). The effect on sleep was very noticeable and it definitely wasn't a placebo. It took me a few weeks to draw a connection to what was messing with my sleep and it stopped when the ZMA ran out.