When the elbow extends, what is primarily happening at the shoulder?

When the elbow extends, the shoulder is primarily participating in an extension movement as well. This is because many of the muscles involved in elbow extension, such as the triceps brachii, have attachments that influence the shoulder joint as well. When the elbow is straightened (extended), the overall position of the arm often results in the shoulder moving into a more extended position.

This is especially evident in movements such as pushing or throwing, where as the elbow straightens, the shoulder also moves backward, contributing to the overall extension of the arm. The kinetic chain effect in the upper limb shows how movements can be interconnected between joints, where one movement can influence the position of another joint in the chain.

The other potential options do not align with this biomechanical relationship, as they assume a different action at the shoulder that is not typical during elbow extension.