Which of the following actions is not classified as flexion?

Flexion refers to a specific type of movement in which the angle between two body segments decreases, effectively bringing those segments closer together. This action is typically observed at joints such as the elbow or knee when they bend.

When considering the options provided, extending the arm in front represents an action that increases the angle at the shoulder joint, moving the arm away from the body rather than bringing it closer. Thus, it does not fit the definition of flexion, which is characterized by the reduction of the angle between adjacent body parts.

The other actions mentioned—bringing two body segments closer together, decreasing the angle at a joint, and reducing the joint angle—are all descriptions that align with the concept of flexion, as they emphasize the reduction in angle at joints. This understanding illustrates that only the action of extending the arm in front is not classified as flexion.