Which of the following is the prime mover for shoulder flexion? Group of answer choices Anterior deltoid Posterior deltoid Which of the following is the prime mover for shoulder flexion? Group of answer choices Anterior deltoid Posterior deltoid Coracobrachialis Long head of the triceps
The Correct Answer and Explanation is :
The correct answer is Anterior deltoid.
Explanation:
Shoulder flexion refers to the movement of the arm forward, in the sagittal plane, where the angle between the arm and the body decreases. For this movement to occur, specific muscles work to produce the motion. The primary muscles involved in shoulder flexion include the anterior deltoid, the coracobrachialis, and to a lesser degree, the pectoralis major. Let’s break down the role of each muscle in shoulder flexion.
- Anterior Deltoid: The anterior (front) part of the deltoid muscle is the primary muscle responsible for shoulder flexion. The deltoid is a large muscle located on the upper arm and shoulder, and it has three distinct parts: anterior, lateral, and posterior. The anterior deltoid fibers are particularly involved when lifting the arm forward. This muscle works by pulling the humerus (upper arm bone) upwards and towards the front of the body, making it the key muscle in shoulder flexion.
- Coracobrachialis: This muscle is located near the front of the shoulder, originating from the coracoid process of the scapula (shoulder blade) and inserting on the humerus. While it does assist with shoulder flexion, it is not as powerful or prominent as the anterior deltoid. It helps with stabilizing the shoulder and flexing the arm slightly, but its contribution is secondary.
- Posterior Deltoid: The posterior (back) part of the deltoid is not involved in shoulder flexion. Instead, it is responsible for shoulder extension, which is the opposite movement—moving the arm backward.
- Long Head of the Triceps: The long head of the triceps is involved in shoulder extension and elbow extension. It crosses both the shoulder and elbow joints but does not play a significant role in shoulder flexion.
In summary, the anterior deltoid is the prime mover for shoulder flexion, and other muscles like the coracobrachialis assist in the motion, while the posterior deltoid and long head of the triceps are not involved in flexion at all.