TRAPEZIUS
Pronounced: Trap-eez-iuss
Origin: 7th cervical vertebra and all thoracic vertebrae
Insertion: Clavicle and scapula
Joints crossed: Shoulder girdle
Direction of fibres: Three different directions
Action: Upper fibres elevate the shoulders and extend the neck. Middle fibres retract the scapula. Lower fibres depress the scapula.
Exercise examples: Shoulder shrugs
The trapezius starts where it attaches to the thoracic and cervical spine, and finishes where it attaches on the scapula and clavicle.
RHOMBOIDS
Pronounced: Rom-boyds
Origin: 7th cervical vertebra and all thoracic 1-5
Insertion: Scapula
Joints crossed: Shoulder girdle
Direction of fibres: Diagonal
Action: Retracts the shoulder girdle and rotates the scapula (internally)
Exercise examples: Pulling shoulder blades together for posture
The rhomboids start where they attach to the thoracic and cervical spine, and finish where they attach on the scapula.
PECTORALIS
Pronounced: Pec-tor-alis
Origin: Clavicle and sternum
Insertion: Humerus
Joints crossed: Shoulder
Direction of fibres: Horizontal
Action: Horizontal flexion, adduction and inward rotation of the arm.
Exercise examples: Press ups and Pec dec
Pectoralis major starts where it attaches to the clavicle and sternum, and finishes where it attaches near the top of the humerus.
DELTOID
Pronounced: Del-toyd
Origin: Clavicle and scapula
Insertion: Humerus
Joints crossed: Shoulder
Direction of fibres: Three sets of fibres running vertically
Action: Abducts the arm and assists in shoulder rotation and flexion.
Exercise examples: Dumbell lateral raise
The deltoid starts where it attaches to the scapula and clavicle, and finishes where it attaches on the side of the humerus.
LATISSIMUS DORSI
Pronounced: La-tiss-i-mus dpr-sy
Origin: Lumbar and sacral vertebrae, thoracic vertebrae 7-12
Insertion: Humerus
Joints crossed: Shoulder
Direction of fibres: Diagonal
Action: Adducts, extends and inwardly rotates the shoulder.
Exercise examples: Lat pull downs
The latissimus dorsi starts where they attach to the lumbar and sacral spine, and finish where they attach near the top of the humerus.
BICEPS
Pronounced: Bi-seps
Origin: Scapula
Insertion: Radius
Joints crossed: Elbow and shoulder
Direction of fibres: Vertical
Action: Flexes the elbow and supinates forearm.
Exercise examples: Bicep curls
The biceps start where they attach to the scapula and finish where they attach just below the elbow onto the radius.
TRICEPS
Pronounced: Tri-seps
Origin: Scapula and humerus
Insertion: Ulna
Joints crossed: Elbow and shoulder
Direction of fibres: Vertical
Action: Extends the elbow.
Exercise examples: Tricep dips
The triceps start where they attach to the scapula and humerus, and finish where they attach just below the elbow onto the ulna.