Prime Mover (Muscle)

Prime Mover: The muscle that can produce the most force for a joint action. Generally, this is the muscle that will generate the most force during a joint action when exerting force against an external load. For example, the gluteus maximus is the prime mover of hip extension during exercises like the Ultimate Glute Bridge , lateral lunge , deadlift , or squat .

• Synonym: Agonist, although this term may be used for any muscle responsible for a joint action.
• Related: The synergists are all the muscles that cause a joint action but are not the prime mover.
• Opposite: The antagonists would be all of the muscles that perform the opposite joint action.
• Special Note: The prime mover, as defined above, may or may not be the most active muscle for a joint action during activities of daily living. For example, the gluteus maximus is the most powerful hip extensor and, therefore, the prime mover; however, the hamstrings are likely the most active hip extensors during low-level activities like walking or standing.

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

List of Prime Movers by Joint Action

Shoulder (Glenohumeral Joint)

• Flexion: Anterior Deltoid
• Extension: Posterior Deltoid
• Abduction: Middle Deltoid
• Adduction: Latissimus Dorsi
• Internal Rotation: Subscapularis
• External Rotation: Infraspinatus
• Horizontal Abduction: Posterior Deltoid
• Horizontal Adduction: Pectoralis Major

2. Elbow (Humeroulnar Joint)

• Flexion: Biceps Brachii, Brachialis, Brachioradialis
• Extension: Triceps Brachii, Anconeus

3. Hip

• Flexion: Iliopsoas
• Extension: Gluteus Maximus
• Abduction: Gluteus Medius
• Adduction: Adductor Longus
• Internal Rotation: Gluteus Minimus
• External Rotation: Gluteus Maximus
• Horizontal Abduction: Piriformis
• Horizontal Adduction: Adductors

4. Knee

• Flexion: Biceps femoris
• Extension: Quadriceps
• Internal Rotation (of flexed knee): Semitendinosus and Semimembranosus
• External Rotation (of flexed knee): Biceps Femoris

5. Ankle (Talocrural Joint)

• Plantarflexion: Soleus
• Dorsiflexion: Tibialis Anterior
• Eversion: Fibularis Muscles
• Inversion: Tibialis Posterior

6. Spine (Lumbar Spine)

• Flexion: Rectus Abdominis
• Extension: Erector Spinae (Spinalis, Longissimus, Iliocostalis)
• Lateral Flexion: External Obliques, Quadratus Lumborum, Erector Spinae (unilaterally)
• Rotation: External Obliques