Module 1 Muscle Actions

Splenius

Bilateral: extension of head neck
Unilateral: lateral flexion and ipsilateral rotation of head and neck

Erector spinae

Bilateral: vertebral column extension
Unilateral: Lateral flexion

Transversospinalis

Bilateral: contributes to vertebral column extension
Unilateral: contralateral rotation

Suboccipitals

Fine postural control, extension & rotation of head at atlanto-occipital and atlanto-axial joints

Quadratus lumborum

Lateral flexion, stabilizes 12 rib and pelvis; contributes to posterior abdominal wall

Rectus abdominus

Trunk flexion, compresses abdominal cavity, stabilizes pelvis

Internal Oblique

Bilateral: trunk flexion, compresses abdomen
Unilateral: Lateral flexion, ipsilateral rotation

External Oblique

Bilateral: trunk flexion, compresses abdomen

Unilateral: Lateral flexion, contralateral rotation

Transverse abdominus

Compresses abdominal cavity, increases intra-abdominal pressure, stabilizes trunk

Psoas Major

hip flexion, trunk flexion with stabilized hip joint

Iliacus

Hip flexion

Sternocleidomastoid

Bilateral: head and cervical neck flexion
Unilateral: lateral flexion and contralateral rotation

Prevertebrals

Bilateral: atlanto-occipital flexion, stabilizes cervical vertebrae
Unilateral: lateral cervical flexion

Scalenes

Bilateral: elevates thoracic cage during forced inspiration
Unilateral: lateral cervical flexion