Trunk

Erector spinae Origin Sacrum; ribs; lumbar, thoracic, and cervical vertebrae Actions: Extension, rotation, and lateral flexion of vertebrae. Provides resistance that helps control the action of bending over at the waist. Insertion Ribs, thoracic and cervical vertebrae, and skull

Iliopsoas Origin Lumbar vertebrae and iliac bone Insertion Lesser trochanter of femur Actions: Hip flexion Spine rotation Keeps upper body from falling over when standing erect.

Foot

Tibialis anterior Origin Proximal tibia Insertion First cuneform and first metatarsal of foot Actions: Dorsiflexion of foot Eversion of foot Stabilization of ankle

Gastrocnemius Actions: Plantar flexion Flexion of the knee Origin Posterior surface of distal head of femur Insertion Posterior surface of calcaneus

Soleus Origin Proximal tibia and fibula Insertion Calcaneus Actions: Plantar flexion

Tibialis posterior Origin Inner posterior borders of tibia and fibula Insertion Navicular, first and third cuneforms, cuboid, and second, third, and fourth metatarsals Actions: Dorsiflexion of foot Eversion of foot Stabilization of ankle