trunk muscles

erector spinae

Extension, lateral flexion, & ipsilateral rotation of spine & head, Anterior pelvic rotation, Lateral pelvic rotation to contralateral side

quadratus lumborum

Lateral flexion to ipsilateral side, Stabilizes pelvis & lumbar spine, Extension of lumbar spine, Anterior pelvic rotation, Lateral pelvic rotation to contralateral side

rectus abdomnis

Both sides: lumbar flexion, Posterior pelvic rotation,

Right side: weak lateral flexion to right,

Left side: weak lateral flexion to left

sternocleidomastoid  

Both sides: extension of head at atlantooccipital joint & flexion of neck

Right side: rotation to left & lateral flexion to right of head & neck

Left side: rotation to right & lateral flexion to left of head & neck