The Back - Muscle Actions

Trapezius

Rotates, elevates (superior part), retracts (middle part), and depresses (inferior part) scapula

Latissimus dorsi

Extends, adducts, and medially rotates humerus

Levator scapulae

Elevates and rotates the scapula to tilt the glenoid cavity inferiorly

Rhomboid major

Retracts and rotates the scapula to tilt the glenoid cavity inferiorly

Rhomboid minor

Retracts and rotates the scapula to tilt the glenoid cavity inferiorly

Serratus posterior superior

Elevates ribs 2-5

Serratus posterior inferior

Depresses ribs 9-12

Splenius capitis

Unilateral - laterally flexes and rotates head or neck to same side; Bilateral - extends head and neck

Splenius cervicis

Unilateral - laterally flexes and rotates head or neck to same side; Bilateral - extends head and neck

Erector Spinae (Spinalis, Longissimus, and Iliocostalis)

Unilateral - laterally flexes vertebral column to same side; Bilateral - extends vertebral column and head, stabilizes vertebral column

Semispinalis capitis

Unilateral - extends and laterally rotates head to opposite side; Bilateral - extends head

Semispinalis cervicis

Unilateral - extends and laterally rotates neck to opposite side; Bilateral - extends neck

Spinotransverse (Rotatores, Multifidus, and Semispinalis)

Extends and rotates vertebral column to opposite side

Levatores coastarum

Elevate ribs in inspiration