In anatomical terms, what does extension generally involve?

Extension, in anatomical terms, refers to the movement that increases the angle between two body segments at a joint. This action typically occurs in several major joints of the body, such as the knee, elbow, and hip. For example, when you straighten your arm after bending it, you are performing an extension at the elbow joint, which increases the angle from the forearm to the upper arm.

This concept is crucial for understanding human movement and biomechanics, especially when it comes to designing exercises and understanding functional movement patterns. Recognizing that extension is about increasing angles allows fitness instructors to better teach clients how to perform exercises correctly and safely, ensuring they engage the appropriate muscle groups and prevent injuries.

The other choices relate to different movements. Decreasing the joint angle refers to flexion, stabilizing a segment pertains to isometric actions, and bringing two body segments closer together describes adduction. These illustrate different types of movements and interactions in the body's musculoskeletal system.