Lesson 8: Introduction To Deltoids

This course describes the deltoid muscles, also known as the shoulder muscles or delts, and how the muscle fibers of the deltoids are divided into “three heads” or “three parts”: anterior head (front delt), middle head (lateral deltoid), and posterior head (rear delt).

Further, this course describes their contribution to motion of the humerus (upper arm bone) at the shoulder joint (glenohumeral joint). This includes the anterior deltoid contributing to shoulder flexion during a front raise or horizontal adduction during a bench press, the middle deltoid (lateral deltoid) contributing to shoulder abduction during a lateral raise or upright row, and the posterior deltoid contributing to shoulder horizontal abduction during a reverse fly or shoulder extension during a seated row. Additionally, this course analyzes the contribution of the deltoid and scapular muscles (shoulder blade muscles) to two of the best exercises for the deltoids, the overhead press, and the reverse fly.

Sports medicine professionals (personal trainers, fitness instructors, physical therapists, massage therapists, chiropractors, occupational therapists, athletic trainers, etc.) must be aware of the deltoid muscle for detailed analysis of human movement, and the development of sophisticated exercise programs and therapeutic (rehabilitation) interventions. Further, this course is essential knowledge for future courses discussing the neural innervations of the deltoids (axillary nerve), the origin and insertion of the deltoids (spine of the scapula, acromion, deltoid tuberosity of the humerus), its synergistic function with other shoulder muscles (e.g. synergy with the rotator cuff, pectoralis major, latissimus dorsi during shoulder motion), injury and physical therapy issues (e.g. shoulder pain, deltoid pain, deltoid strain, hypertonic deltoid muscle fibers, trigger points, etc.), and sports performance (e.g. max bench press, throwing, shooting, punching, lifting).

For more advanced anatomy check out our integrated functional anatomy courses:

• Deltoids

Caption: The deltoid muscles attaching from the scapula to the humerus