Chap. LXXXVIII.—Of the Motions of a Man.
When you mean to represent a man removing a weight, consider that the motions are various, viz. either a simple motion, by bending himself to raise the weight from the ground upwards, or when he drags the weight after him, or pushes it before him, or pulls it down with a rope passing through a pulley. It is to be observed, that the weight of the man’s body pulls the more in proportion as the centre of his gravity is removed from the centre of his support. To this must be added the strength of the effort that the legs and back make when they are bent, to return to their natural straight situation.
A man never ascends or descends, nor walks at all in any direction, without raising the heel of the back foot.