I agree with you, Unclejed.
But all deppends on the frequency.
Our muscles respond very well to 50/60 Hz mains, so, for example, if I get electrocuted by touching a 220V 60Hz energized wire metallic rod with the palm of my hand, my muscles will respond very well and my hand will hold so tight that I'll be "glued" to the piece.
So, our muscles will behave like they would behave with DC, locking up.
But, for example, if it was a 220V 6kHz, then my muscles would not respond.