When the contraction of a muscle increases the angle between two articulated bones, the movement is defined as:

The movement defined as the contraction of a muscle that increases the angle between two articulated bones is known as extension.

In anatomical terms, extension refers to the straightening of a joint, which results in the angle between the bones increasing. This movement contrasts with flexion, where the angle decreases. For example, when you straighten your elbow after bending it, you are performing an extension movement.

Extension is important in various activities and plays a vital role in improving joint mobility and muscular strength. It is commonly observed in actions such as standing up, kicking, and reaching downward. Understanding these movements is essential in fields such as biology, physiotherapy, and sports science, where they impact physical performance and rehabilitation practices.