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Muscle Function

The main framework of the body (skeleton) is covered by muscles, whose function is to permit movement and maintain posture. Sensory receptors in the muscles monitor the tension and length of the muscles and provide the nervous system with information about the position of the body parts, thereby enabling posture to be maintained.

Movement Definitions

Each of the movements of the muscles for the various parts of the body is described by various terms.

  • Abductor - moves a limb away from the midline
  • Adductor - moves a limb towards the midline
  • Extensor - increase the angle at a joint - extends a limb
  • Flexor - decreases the angle at a joint - flexes a limb
  • Pronator - turns a limb to face downwards
  • Supinator - turns a limb to face upwards
  • Rotator - rotates a limb
  • Sphincter - closes an orifice of opening

Muscle actions

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 - Adducts scapular and rotates it inwards
  • Serratus anterior - Stabilises 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
  • Teres major - Extends arm, assists in adduction and medial rotation of arm

Muscles which move the forearm and wrist 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
  • Pronator teres - Pronates and flexes forearm
  • Pronator quadratus - Pronates the forearm and hand
  • Supinator - Supinates forearm and hand

Muscles which move the abdominal wall and their action

  • Rectus abdominis - Compresses abdomen and flexes vertebral column
  • External obliques - Bends vertebral column laterally and rotates vertebral column
  • Transversus abdominis - Compresses abdomen
  • Quadratus lumborum - Side flexion

Muscles which move the vertebral column and their action

  • Iliocostalis lumborum - Extends lumbar region
  • Iliocostalis thoracis - Maintains the spine's erect position
  • Iliocostalis cervicis - Extends cervical region
  • Longissimus thoracis - Extends thoracis 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

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 rotates thigh laterally.
  • Adductor longus - Adducts, medially rotates and flexes the thigh
  • Adductor brevis - Adducts, laterally rotates and flexes the thigh
  • Adductor magnus - 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

Muscles which move the foot and their action

  • Tibialis anterior - Dorsiflexes and inverts foot
  • Peroneus tertius - Dorsiflexes and everts foot
  • 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

Related References

The following references provide additional information on this topic:

  • EDWARDS, R. H. (1981) Human muscle function and fatigue. Human muscle fatigue: physiological mechanisms, p. 1-18.
  • Edwards, R. H. et al. (1977) Human skeletal muscle function: description of tests and normal values. Clin Sci Mol Med52 (3), p. 283-290
  • BOLAND, R. (1986) Role of Vitamin D in Skeletal Muscle Function. Endocrine reviews7 (4), p. 434-448

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • MACKENZIE, B. (2006) Muscle Function [WWW] Available from: [Accessed

Related Pages

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