Pro's Corner

Muscle Actions

by Florent Krasniqi

Muscles which move the shoulder and their action

  • Levator scapulae – Raises shoulder blade
  • Pectoralis minor – Lowers shoulder blade
  • Trapezius – Lifts clavicle. Adducts, elevates and rotates scapular outwards
  • Rhomboideus major the minor – Adducts scapular and rotates it inwards
  • Serratus anterior –  Stabilizes scapula when hand exerts pressure on an object

Muscles which move the arm and their action

  • Pectoralis major - Flexes, adducts and rotates arm medially
  • Latissimus dorsi – Extends, adducts and rotates arm medially. Moves arm downward and backwards
  • Deltoid – Abducts, flexes, extends and medially and laterally rotates arm
  • Coracobrachialis – flexes and adducts arm
  • Teres major -  Extends arm, assists in adduction and medial rotation of arm
  • Subscapularis – adducts arm and rotates arm medially
  • Supraspinatus - abducts arm and rotates arm laterally
  • Infraspinatus - abducts arm and rotates arm laterally
  • Teres minor - abducts arm and rotates arm laterally

Muscles which move the forearm and their action

  • Biceps brachii - Flexes and supinates forearm. Flexes arm
  • Brachialis - Flexes the forearm
  • Brachoradialis - Flexes, semi-supinates and semi-pronates the forearm
  • Triceps brachii - Extends forearm. Extends arm
  • Anconeus – Extends forearm. Extends arm.
  • Pronator teres - Pronates and flexes forearm
  • Pronator quadratus - Pronates the forearm and hand
  • Supinator - Supinates forearm and hand

Muscles which move the wrist and fingers and their action

  • Flexor carpi radialis - Flexes and abducts wrist
  • Palmaris longus - Flexes wrist and tenses palmar aponeurosis
  • Flexor carpi ulnaris - Flexes and adducts wrist. Fixes pisiform during action of hypothenar muscles
  • Flexor digitorum superficialis - Flexes proximal interphalangeal joints and secondarily metacarpophalangeal joints and wrist
  • Flexor digitorum profundus - Flexes distal interphalangeal joints, then secondarily flexes proximal interphalangeal and metacarpophalangeal joints and wrist
  • Extensor carpi radialis longus and brevis - Extends and abducts hand at wrist
  • Extensor digitorum - Extends all joints of fingers
  • Extensor pollicis longus and brevis - Extends interphalangeal and metacarpophalangeal joints of thumb
  • Extensor indicis – Extends all joints of index finger
  • Abductor pollicis brevis - Abducts thumb at metacarpophalangeal & carpometacarpal joints
  • Adductor pollicis - Adducts carpometacarpal joint of thumb
  • Opponens pollicis - Opposes (medially rotates and flexes ) carpometacarpal and metacarpophalangeal joints of thumb
  • Flexor pollicis brevis – Flexes metacarpophalangeal joint of thumb
  • Flexor policis longus - Flexes distal phalanx of thumb
  • Palmaris brevis – Steadies and corrugates skin of palm to help with grip
  • Abductor digiti minimi – Abducts little finger at metacarpophalangeal joint
  • Flexor digiti minimi – Flexes metacarpophalangeal joint of little finger
  • Opponens digiti minimi – Opposes (flexes and laterally rotates) carpometacarpal and metacarpophalangeal joints of little finger
  • Interrosei palmares - Adduct to axis of middle finger. Flex metacarpophalangeal joint while extending interphalangeal joints
  • Interrosei dorsales – Abduct from axis of middle finger. Flex metacarpophalangeal joint while extending interphalangeal joints
  • Lumbricales – Flex metacarpophalaneal joints and extend interphalangeal joints of fingers

Muscles which move the abdominal wall and their action

  • Rectus abdominis - Compresses abdomen and flexes vertebral column
  • Pyramidalis - Reinforces lower rectus sheath
  • External and internal obliques - Bends vertebral column laterally and rotates vertebral column
  • Transversus abdominis - Compresses abdomen
  • Quadratus lumborum - Side flexion

Muscles which move the ribs (respiratory muscles) and their action

  • Intercostales externi - Fix intercostal spaces during respiration. Aids forced inspiration by elevating ribs
  • Intercostales interni - Fix intercostal spaces during expiration. Aids forced inspiration by elevating ribs
  • Levatores costarum - Elevates ribs
  • Subcostales - Depresses lower ribs
  • Transversus thoracis - Depresses upper ribs
  • Serratus posterior superior – Assists forced inspiration
  • Serratus Posterior Inferior – Assists forced expiration
  • Diaphragm - Inspiration and assists in raising intra-abdominal pressure

Muscles which move the vertebral column and their action

  • Iliocostalis lumborum - Extends lumbar region
  • Iiocostalis thoracis – Maintains the spine's erect position
  • Iliocostalis cervicis – Extends cervical region
  • Longissimus thoracis – Extends thoracic region
  • Longissimus cervicis – Extends cervical region
  • Longissimus capitis – Extends the head and rotates it to opposite side
  • Spinalis thoracis – Extends vertebral column
  • Spinalis cervicis - Extends vertebral column
  • Spinalis capitis - Extends vertebral column
  • Psoas minor - Weak flexor of vertebral column

Muscles which move the thigh and their action

  • Psoas major - Flexes and rotates thigh medially and flexes vertebral column
  • Iliacus - Flexes and rotates thigh medially and flexes vertebral column
  • Gluteus maximus – Extends and laterally rotates hip. Maintains knee extended via iliotibial tract
  • Gluteus medius - Abducts and medially rotates hip. Tilts pelvis on walking
  • Gluteus minimus - Abducts and medially rotates hip. Tilts pelvis on walking.
  • Tensor fascia latae - Maintains knee extended (assists gluteus maximus) and abducts hip
  • Gracilis - Adducts hip. Flexes knee and medially rotates flexed knee
  • Pectineus – Flexes, adducts and medially rotates hip
  • Gemellus inferior – laterally rotates and stabilizes hip
  • Gemellus superior - laterally rotates and stabilizes hip
  • Quadratus femoris - laterally rotates and stabilizes hip
  • Piriformis - laterally rotates and stabilizes hip
  • Obturatorius internus - laterally rotates and stabilizes hip
  • Obturatorius externus - laterally rotates hip
  • Adductor longus - Adducts, medially rotates and flexes the thigh
  • Adductor brevis - Adducts, laterally rotates and flexes the thigh
  • Adductor magnusv - Adducts, flexes, laterally rotates and extends the thigh.

Muscles which act on the leg and their action

  • Rectus femoris - Extends knee and flexes hip
  • Vastus lateralis - Extends knee
  • Vastus medialis - Extends knee
  • Vastus intermedius - Extends knee
  • Sartorius - Flexes knee. Flexes hip and rotates femur laterally
  • Biceps femoris - Flexes leg and extends thigh
  • Semitendinosus - Flexes leg and extends thigh
  • Semimembranosus - Flexes leg and extends thigh
  • Popliteus - Unlocks extended knee by lateral rotation of femur on tibia. Pulls back lateral meniscus

Muscles which move the foot and fingers and their action

  • Tibialis anterior - Dorsiflexes and inverts foot
  • Peroneus tertius - Dorsiflexes and everts foot
  • Extensor hallucis longus – Extends big toe and foot. Inverts foot and tightens subtalar joints
  • Extensor digitorum longus - Extends toes and extends foot at ankle
  • Gastrocnemius - Plantar flexes foot and flexes knee
  • Soleus - Plantar flexes foot
  • Plantaris - Plantar flexes foot
  • Tibialis posterior - Plantar flexes and inverts the foot
  • Peroneus longus - Plantar flexes and everts the foot
  • Peroneus brevis - Plantar flexes and everts the foot
  • Flexor digitorum longus - Flexes distal phalanges of lateral four toes and foot at ankle. Supports lateral longitudinal arch
  • Flexor hallucis longus - Flexes distal phalanx of big toe, flexes foot at ankle, supports medial longitudinal arch
  • Plantaris – plantar flexes foot and also flexes the leg at the knee
  • Extensor digitorum brevis - Extends toes when foot fully dorsiflexed
  • Adductor hallucis –Adducts and flexes metatarsophalangeal joint of big toe. Supports transverse arch
  • Flexor hallucis brevis - Flexes metatarsophalangeal joint of big toe. Supports medial longitudinal arch
  • Abductor hallucis - Flexes and abducts big toe. Supports medial longitudinal arch
  • Flexor digitorum brevis - Flexes lateral four toes, Supports medial and lateral longitudinal arches
  • Lumbricales - Extend toes at interphalangeal joints and flex metatarsal phalangeal joints
  • Interrossei – dorsal of foot-Abduct 2nd, 3rd and 4th toes from axis of 2nd toe. Assist lumbricals in extending interphalangeal joints while flexing metatarsal phalangeal joints
  • Interrossei – plantar of foot -Adduct 3rd 4th and 5th toes to axis of 2nd toe, Assist lumbricals in extending interphalangeal joints while flexing metatarsal phalangeal joints