Which muscle is primarily responsible for extending the elbow?

The muscle that is primarily responsible for extending the elbow is the triceps brachii. This muscle is located at the back of the upper arm and is composed of three heads, or points of origin: the long head, lateral head, and medial head. When the triceps contracts, it pulls on the ulna bone of the forearm, thus extending the elbow joint. This action is vital for various movements, including pushing and straightening the arm.

In contrast, the biceps are primarily responsible for flexing the elbow, while the deltoid primarily functions to facilitate shoulder movements rather than elbow extension. The forearm muscles, while they play key roles in various functions of the arm and wrist, do not specifically extend the elbow joint. Understanding the specific roles of these muscles is essential for comprehending biomechanics and applying this knowledge in massage therapy and other physical activities.