Muscle Actions You Need to Know

External intercostals

Elevates ribs for inspiration

Occipital belly of Occipitofrontalis

Tenses and retracts scalp

Flexor digitorum longus

Flexion of toes (digits II-V)

Gluteus maximus

Extension and lateral rotation at hip joint; Also helps tense iliotibial band to laterally support knee

Semimembranosus

Extension at hip joint and flexion at knee

Supraspinatus

Abduction at shoulder joint

Subscapularis

Medial rotation at shoulder joint

Mentalis

Protrudes lower lip, wrinkles skin of chin (pout)

Longissimus thoracis

Extension of spine with bilateral contraction; lateral flexion of spine

with unilateral contraction

Extensor pollicis longus

Extension of pollex

Zygomaticus major

Draws angle of mouth upward (elevates) and laterally (retracts) as in laughing

Sartorius

Flexes and laterally rotates at hip, and flexes knee

Levator labii superioris

Elevates upper lip (snarl)

Buccinator

Compresses cheek medially

Pectoralis major

Flexion, adduction and medial rotation at shoulder

Flexor hallucis longus

Flexion of hallux

Soleus

Plantar flexion at ankle

Tensor fasciae latae (TFL)

Flexion and slight medial rotation at hip;

tenses iliotibial band to laterally support knee

Extensor carpi ulnaris

Extension and adduction (ulnar deviation) at wrist

Gemellus inferior

Lateral rotation at hip

Semispinalis capitis

Extension of head and neck with bilateral

contraction; extension, lateral flexion and

rotation of neck if one side contracts

(unilateral contraction)

Pronator teres

Pronates forearm and slightly

flexes elbow

Frontal belly of Occipitofrontalis

(Frontalis muscle)

Raises eyebrows, wrinkles forehead

Biceps femoris

Extension at hip joint (long head only) and flexion at knee

Extensor carpi radialis longus

Extension and abduction (radial deviation) at wrist

Splenius capitis

Extension of head and neck with bilateral

contraction; lateral flexion and rotation of

head and neck with unilateral contraction

Anterior scalene

Flexion of neck and head with bilateral contraction; lateral

flexion with contralateral rotation of neck if one side

contracts (unilateral contraction)

Also is accessory muscle of inspiration

Peroneus (fibularis) longus

Eversion of foot and plantar flexion at ankle

Internal intercostals

Depresses ribs for forced expiration

Levator scapulae

Elevation of scapula

Triceps brachii

Extends at elbow; long head

also extends at shoulder joint

Extensor digitorum

Extension of digits II-V and wrist

Latissimus dorsi

Extension, adduction and

medial rotation at shoulder

Vastus medialis

Extension at knee

Orbicularis oris

Closes and protrudes lips

(pucker)

Psoas major

Flexion of thigh at hip; Can also

flex lumbar spine if hip

stabilized

Sternocleidomastoid

Flexion of neck and head with bilateral contraction;

lateral flexion with contralateral rotation of neck if one

side contracts (unilateral contraction)

Biceps brachii

Flexion at elbow and supination of

forearm at proximal radio-ulnar

joint

Extensor carpi radialis brevis

Extension and abduction (radial

deviation) at wrist

Gluteus minimis

Abduction and slight medial

rotation at hip

Flexor pollicus longus

Flexion of pollex

Gastrocnemius

Plantar flexion at ankle; and

flexion at knee

Masseter

Elevates mandible

Semitendinosus

Extension at hip joint and

flexion at knee

Brachioradialis

Flexion at elbow

Palmaris longus

Flexes wrist

Iliacus

Flexion of thigh at hip

Adductor longus

Adduction and flexion at hip;

helps with rotation of femur

Teres major

Extension and Medial rotation

at shoulder

Temporalis

Elevates mandible

Rhomboid minor

Retraction of scapula

Gemellus superior

Lateral rotation at hip

Extensor digiti minimi

Extends 5th digit

Extensor pollicis brevis

Extension of pollex

Orbicularis oculi

Closes eye (squeezes shut)

Quadratus femoris

Lateral rotation at hip

Supinator

Supinates forearm

Tibialis posterior

Plantarflexion at ankle and

inversion of foot

Vastus lateralis

Extension at knee

Serratus anterior

Protracts scapula

Obturator internus

Lateral rotation at hip

Quadratus lumborum

Lateral flexion of vertebral

column

Vastus intermedius

Extension at knee

Flexor carpi radialis

Flexion and abduction (radial

deviation) at wrist

Extensor digitorum longus

Extension of toes (digits II-V)

Diaphragm

Primary muscle of inspiration

Flexor digitorum profundus

Flexion of distal phalanges (II-V)

Brachialis

Flexion at elbow

Posterior scalene

Flexion of neck and head with bilateral contraction; lateral

flexion with contralateral rotation of neck if one side

contracts (unilateral contraction)

Also is accessory muscle of inspiration

Flexor digitorum superficialis

Flexion of digits II-V and wrist

Coracobrachialis

Adduction and slight flexion at

shoulder

Flexor carpi ulnaris

Flexion and adduction (ulnar

deviation) at wrist

Pectineus

Flexion and adduction at hip

Pectoralis minor

Protraction and depression of

scapula

Gluteus medius

Abduction and slight medial

rotation at hip

Rhomboid major

Retraction of scapula

Teres minor

Lateral rotation at shoulder joint

Adductor magnus

Adduction and extension at hip;

helps with rotation of femur

Infraspinatus

Lateral rotation at shoulder joint

Peroneus (fibularis) brevis

Eversion of foot

Piriformis

Lateral rotation at hip

Extensor hallucis longus

Extension of hallux

Middle scalene

Flexion of neck and head with bilateral contraction; lateral

flexion with contralateral rotation of neck if one side

contracts (unilateral contraction)

Also is accessory muscle of inspiration

Abductor pollicis longus

Abduction of pollex and wrist

Gracilis

Adduction and slight medial

rotation at hip, helps with flexion of knee

Popliteus

Slight medial rotation of tibia to

help “unlock” knee after

standing

Rectus femoris

Flexion at hip and extension at

knee

Tibialis anterior

Dorsiflexion at ankle and

inversion of foot

Deltoid

Abduction at shoulder joint, also can

flex (anterior fibers) or extend

(posterior fibers) at shoulder

Risorius

Draws corners of mouth

laterally, as in smiling

Trapezius

Elevation, retraction and/or

depression of scapula; can also

extend head and neck