So I couldn't sleep and was playing the old 'maybe if I try hard enough my muscles will move' game. I realized that maybe I can pull my left leg up towards my body, I've been doing this for ages, mostly to pull my left leg up over my other leg when lying on my right side, and always assumed it was just a functional spasm that I was able to trigger reliably.
I realized I can also do it when lying on my back, I just concentrate very hard, almost straining every fiber in my body, and my leg will straighten and shake before I am able to pull it up.

How to tell if its voluntary or a spasm? Would I always be able to trigger the spasm every time?