Actually I meant to say that you would not see too much squirming around if nailed to a cross. Like the girls hanging down with their arms stretched out taut. Some pushing up but not a lot of wild frantic motion. Too painful I would think with raw flesh moving against the solid iron nails. The condemned would try to limit their movements to what is absolutely essential as when needed to breathe or when muscle cramps get too bad. Their bodies would be in a fearful state of tension from the beginning.
But who knows. No time machine to go back and see what a real crucifixion was like. (Except maybe crumera, who seems to have some insights. Perhaps he could enlighten us further.)