Antagonists (Muscle)

Antagonists: Muscles that oppose the agonists (including the prime mover and synergists) for a given joint action. That is, all the muscles that can perform the opposing joint action. For example, the triceps are antagonists to the biceps during elbow flexion.

• Synonym: Opposing muscles.
• Opposite: The agonists would be all of the muscles that perform the opposite joint action.
• Special Note: Sometimes, the term "functional antagonist" is used to refer to a special case in which muscles oppose one another for a specific joint action or during a specific motion, but they do not oppose each other for all joint actions. For example, the tibialis posterior and fibularis muscles will both contribute to plantar flexion; however, they are functional antagonists in the frontal plane, as the tibialis posterior performs inversion, and the fibularis muscles perform eversion.

For additional information, including a video lecture:

• Lesson 21: Functional Roles of Muscles

Functional Roles of Muscles Glossary Terms:

• Prime Mover
• Agonist
• Synergist
• Antagonist
• Neutralizer
• Fixator
• Stabilizer

Articles listing all of the muscles by functional role for each joint action:

• Kinesiology of the Shoulder and Scapula
• Kinesiology of the Elbow
• Kinesiology of the Trunk
• Kinesiology of the Hip
• Kinesiology of the Knee
• Kinesiology of the Ankle

Examples of Joint Actions, Agonists, and Antagonists

Shoulder Flexion

• Agonists:
  • Anterior deltoid
  • Pectoralis major (clavicular head)
  • Coracobrachialis
  • Biceps brachii (long head)
• Antagonists:
  • Posterior deltoid
  • Latissimus dorsi
  • Teres major

Shoulder Extension

• Agonists:
  • Posterior deltoid
  • Latissimus dorsi
  • Teres major
  • Triceps brachii (long head)
• Antagonists:
  • Anterior deltoid
  • Pectoralis major (clavicular head)

Hip Flexion

• Agonists:
  • Iliopsoas (Psoas major and Iliacus)
  • Rectus femoris
  • Sartorius
  • Tensor fasciae latae
• Antagonists:
  • Gluteus maximus
  • Hamstrings (Biceps femoris, Semitendinosus, Semimembranosus)

Hip Extension

• Agonists:
  • Gluteus maximus
  • Hamstrings (Biceps femoris, Semitendinosus, Semimembranosus)
• Antagonists:
  • Iliopsoas
  • Rectus femoris

Plantarflexion

• Agonists:
  • Gastrocnemius
  • Soleus
  • Tibialis posterior
  • Flexor hallucis longus
  • Flexor digitorum longus
• Antagonists:
  • Tibialis anterior
  • Extensor digitorum longus
  • Extensor hallucis longus

Dorsiflexion

• Agonists:
  • Tibialis anterior
  • Extensor digitorum longus
  • Extensor hallucis longus
• Antagonists:
  • Gastrocnemius
  • Soleus
  • Tibialis posterior