An extension past the anatomical position is known as hyperextension.
What is anatomical position?
An anatomical position can be defined as the position whereby the body is standing upright and facing forward with each arm hanging on either side of the body, and the palms facing forward.
This position is used to study the structure and function of different parts of the organ systems of the body in anatomy.
When the body is extended past the normal range for an anatomical position, it's called hyperextension.