Muscle Actions

Question 1

Gluteus Maximus

Answer 1

• Extension and lateral rotation of the hip
• Upper fibres: abduction
• Lower fibres: adduction

Question 2

Gluteus Medius

Answer 2

• Abduction of the hip
• Anterior fibres: flexion and medial rotation of the hip
• Posterior fibres: extension and lateral rotation of the hip

Question 3

Psoas Major

Answer 3

• Flexion of the hip
• Flexion and ipsilateral side-bending (flexing) of the trunk

Question 4

Iliacus

Answer 4

• Flexion of the hip
• Anterior rotation of the pelvis (potentially one-sided)

Question 5

Tensor Fascia Lata (TFL)

Answer 5

• Flexion, abduction, and medial rotation of the hip

Question 6

Rectus Femoris

Answer 6

• Flexion of the hip
• Extension of the knee

Question 7

Biceps Femoris

Answer 7

• Short head: flexion and lateral rotation of the knee
• Long head: extension and lateral rotation of the hip

Question 8

Adductor Magnus

Answer 8

• Generally adduction of the hip
• Adductor part: flexion and lateral rotation of the hip
• Hamstrings part: extension and medial rotation of the hip

Question 9

Gastrocnemius & Soleus

Answer 9

• Plantarflexion of the talocrural joint
• Flexion of the knee (Gastrocnemius only)

Question 10

Tibialis Posterior

Answer 10

• Plantarflexion of the talocrural joint
• Inversion of the subtalar joint
• Acts to stabilize and maintain balance (dynamic support of the medial arch of the foot)

Question 11

Tibialis Anterior

Answer 11

• Dorsiflexion of the talocrural joint
• Inversion of the subtalar joint
• Acts to stabilize and maintain balance (dynamic support of the medial arch of the foot)

Question 12

Deltoids

Answer 12

• Abduction of the glenohumeral joint
• Anterior fibres: assist in flexion and medial rotation
• Posterior fibres: assist in extension and lateral rotation

Question 13

Biceps Brachii

Answer 13

• Flexion of the glenohumeral joint
• Flexion and supination of the elbow

Question 14

Triceps Brachii

Answer 14

• Extension and adduction of the glenohumeral joint
• Extension of the elbow

Question 15

Pectoralis Major

Answer 15

• Flexion, adduction, and medial rotation of the glenohumeral joint

Question 16

Pectoralis Minor

Answer 16

• Depression, downward rotation, and protraction of the scapula

Question 17

Trapezius

Answer 17

• Superior fibres: elevation and upward rotation of the scapula, bilateral cervical spine extension, ipsilateral head side-bending, and contralateral rotation of the face
• Middle fibres: retraction of the scapula
• Inferior fibres: depression of the scapula

Question 18

Levator Scapula

Answer 18

• Elevation and downward rotation of the scapula
• Extension and ipsilateral side flexion and rotation of the neck

Question 19

Sternocleidomastoid

Answer 19

• Unilateral: ipsilateral lateral flexion of the cervical spine and contralateral rotation
• Bilateral: extends neck at atlantooccipital joints; extends superior cervical vertebrae while flexing inferior vertebrae so the chins is thrust forward with the head kept level

Question 20

Serratus Anterior

Answer 20

• Protraction and upward rotation of the scapula
• Holds the scapula against the thoracic wall

Question 21

Subscapularis

Answer 21

• Internal rotation of the glenohumeral joint
• Stabilization of the humeral head

Question 22

Supraspinatus

Answer 22

• Abduction of the glenohumeral joint
• Stabilization of the humeral head

Question 23

Infraspinatus

Answer 23

• External rotation of the glenohumeral joint
• Stabilization of the humeral head

Question 24

Teres Minor

Answer 24

• Lateral rotation of the glenohumeral joint
• Stabilization of the humeral head

Question 25

Rhomboids

Answer 25

- Elevation, retraction, and downward rotation of the scapula

Question 26

Latissimus Dorsi

Answer 26

- Extension, adduction, and internal rotation of the glenohumeral joint - Anterior rotation of the pelvis

Question 27

Rectus Abdominis

Answer 27

- Flexion of the vertebral column