Major Muscle Functions

Sternocleidomastoid

Turns and flexes head

Masseter

Closes jaw (chewing)

Orbicularis oculi

closes eyes

zygomaticus

smiling

diaphragm

breathing (increases chest space)

intercostals

Move ribs

transversus abdominis

compresses abdomen

rectus abdominis

flexes trunk (“six-pack”)

deltoid

lifts arm

trapezius

moves and stabilizes scapula

rhomboids

pull scapula back

serratus anterior

holds scapula against ribs

latissimus dorsi

pulls arm down/back

biceps brachii

flexes elbow

brachialis

main elbow flexor

triceps brachii

extends elbow

flexor muscles

bend wrist/fingers

extensor muscles

straighten wrist/fingers

opponens pollicis

thumb to fingertips (grip!)

Gluteus maximus

hip extension

gluteus medius

hip abduction and balance

iliopsoas

hip flexion

adductors

bring leg inward

quadriceps

extend knee

hamstrings

bend knee and extend hip

sartorius

crosses legs

gastrocnemius

powerful plantar flexion (jumping)

soleus

posture and standing

tibialis anterior

dorsiflextion (lift foot)

fibularis (peroneus) longus

eversion + plantarflexion

flexor hallucis Longus

bends big toe

extensor digitorum longus

extends toes