Contrapposto is the Italian word used to describe the way in which the different parts of the human body are counterpoised - balanced against each other.
An ability to represent this natural tendency was seen as part of the artist's skill in recording human anatomy in action, a skill much prized during the Renaissance when interest in anatomy and in the nude increased, especially in Italy.
But the movement and variety which complex contrapposto could entail are associated with the figura serpentinata favoured by Mannerist artists and has more to do with what is balletically possible than with movements commonly observed.