GENERAL INFORMATION
The deltoid is a large, triangular-shaped muscle situated in the shoulder region, pivotal for shoulder movement and aesthetics. Comprising anterior (front), middle, and posterior (rear) heads, it plays a central role in shoulder joint function.
ORIGIN
- Anterior Head: Originates from the lateral third of the clavicle.
- Middle Head: Originates from the acromion process of the scapula.
- Posterior Head: Originates from the spine of the scapula.
INSERTION POINT
It inserts into the deltoid tuberosity of the humerus (upper arm bone), facilitating shoulder movement.
MAJOR ARTERIES
This muscle receives vascular supply from branches of the posterior circumflex humeral artery and the thoracoacromial artery, ensuring adequate blood flow for muscle function.
NEURAL INNERVATION
Innervated by the axillary nerve (C5-C6) from the brachial plexus, It receives sensory and motor innervation crucial for shoulder movement and stability.
TRIGGER POINT
Trigger points in this muscle can cause localised pain and tenderness, often due to overuse, poor posture, or trauma.
CONCENTRIC FUNCTION
Contraction of the deltoid muscle facilitates shoulder abduction (lifting the arm away from the body), flexion (lifting the arm forward), and extension (pulling the arm backwards), essential for various upper limb movements.
ECCENTRIC FUNCTION
It provides controlled eccentric movement during shoulder actions, assisting in the controlled descent of the arm.
ISOMETRIC FUNCTION
Isometric contraction of this muscle stabilises the shoulder joint, supporting posture and overall shoulder function.
RELATED MUSCLE SCIENTIFIC NAMES
- Deltoid Muscle: Primary muscle responsible for shoulder movement and stability.
ANTAGONIST MUSCLES
- Latissimus Dorsi: Counters deltoid actions, aiding in shoulder adduction and extension.
- Pectoralis Major: Antagonizes deltoid function during shoulder adduction and flexion movements.
COMMON INJURIES
- Rotator Cuff Injuries: Strains or tears of the rotator cuff tendons can impact deltoid function, often due to repetitive overhead motions.
- Shoulder Impingement: Compression of shoulder structures, including the deltoid, leading to pain and reduced range of motion.
- Shoulder Dislocation: Partial or complete displacement of the humerus from the shoulder socket, potentially causing deltoid strain or tear.
EXERCISES
- Shoulder Press: Weightlifting exercise targeting this muscles, enhancing shoulder strength and stability.
- Lateral Raises: Isolation exercise focusing on shoulder abduction, specifically targeting the middle deltoid.
- Front Raises: Exercise emphasising shoulder flexion, predominantly engaging the anterior deltoid.
- Upright Rows: A compound exercise involving the deltoids and other muscles, performed with dumbbells or a barbell.
STRETCHES
- Across-the-Chest Stretch: Stretches the deltoid by crossing one arm over the chest and gently pulling it towards the body.
- Overhead Triceps Stretch: Extends the deltoid and triceps by reaching one arm overhead, bending at the elbow, and gently pulling the elbow with the opposite hand.
- Wall Stretches: Places the hand on a wall at shoulder height and rotates the body away to stretch the deltoid and shoulder muscles.
- Child’s Pose: Stretches the muscle and relaxes shoulder muscles, supporting flexibility and recovery.