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 –
Posterior shoulder stretch - Example strengthening exercises – Lateral raise
Front raise