Which muscle action occurs when the angle of a joint is increased?

When the angle of a joint is increased, the action occurring at that joint is known as extension. This movement involves the straightening of a joint or the increase in the angle between the body parts that converge at that joint. For instance, when you straighten your arm from a bent position at the elbow, you are executing an extension action.

This action is fundamental in many physical activities and is often contrasted with flexion, which decreases the angle of a joint. Therefore, understanding extension is vital in areas like strength training, movement analysis, and physical rehabilitation, as it plays a role in developing range of motion and strength in various exercises.