1. Naming muscles according to their action
Sanjaya Adikari
Department of Anatomy
Faculty of Medicine
Peradeniya

2. Origin and insertion
Origin – Proximal attachment where there is less movement
Insertion – Distal attachment where there is greater movement
Use the terms, proximal/ distal attachment to avoid confusions

3. Prime mover & antagonist
Prime mover is the muscle that does the desired movement at a joint
Antagonist is the muscle that has the action opposite to that of prime mover
Eg:- Flexion of the elbow joint
Biceps brachii is a prime mover
Triceps is the antagonist

4. Prime mover & antagonist…

5. Synergist
Synergist assists the prime mover by preventing unwanted movements at other joints
Eg:- Flexion of the fingers
Flexor digitorum profundus and superficialis are the prime movers
Extensor muscles of the wrist joint are the synergists

6. Synergists…

7. Synergists… Eg:- Supination of the pronated forearm
Biceps brachii and spinator are the prime movers
Triceps acts as a synergists of biceps to prevent flexion of the elbow joint

8. Synergists… Eg:- Flexion of the elbow joint
Biceps brachii is a prime mover
Posterior fibres of deltoid acts as a synergist to prevent extension of the shoulder joint

9. Fixators
Fixators stabilize one attachment of a muscle so that the contraction moves the other end
Eg:- Abduction of the shoulder joint
Deltoid is the prime mover
Levator scapulae, rhomboids and trapezius are fixators

10. Fixators… Eg:- Abduction of the little finger
Abductor digiti minimi is the prime mover
Flexor carpi ulnaris acts as a fixator of pisiform bone