Deltoid
The deltoid muscle is used in all side lifting movements and any movement of the humerus on the scapula. It is divided into three portions, anterior, middle and posterior, with the fibres having different roles due to their orientation.
Origin
- Outer 1/3 of the clavicle
- Acromion process
- Spine of the scapula
Insertion
- Deltoid tuberosity on the humerus
Actions
- Anterior portion - Shoulder flexion and internal rotation
- Posterior portion - Shoulder extension and external rotation
- All fibres - Shoulder abduction
Innervation
- Axillary nerve
Daily uses
- Lifting
Example stretches
- Anterior shoulder stretch
- Posterior shoulder stretch
Example strengthening exercises
- Lateral raise
- Front raise
Related injuries
- Deltoid strain
Related muscles
- Infraspinatus Supraspinatus
