Functional Groups of
Muscles
S
S Prime movers (agonist)
S Antagonist
S Synergists
S Fixator
S 1 muscle can be in all 4 groups
Interaction of skeletal muscles
S Skeletal muscles either work together or in opposition
S Remember, muscles can only pull (never push)
S As muscles shorten, the insertion point generally moves
toward the origin
S Whatever a muscle (or muscle group) does, another muscle
(or group) ‘un-does’
Functional Groups
S Prime Mover
S Provides the major force for producing a specific movement
S -Ex: Bicep Brachii is the prime mover when you flex your arm
at the elbow
Functional Groups
S Antagonist
S Opposes or reverses a particular movement
S Regulates the motion of the prime mover by contracting and
providing resistance
S Ex: Triceps is the antagonist for flexing the arm at the elbow
S *Prime movers and antagonists are located on opposite sides of
a joint across which they act
Functional Groups
S Synergists
S Help and assist prime movers
S Add extra force to a movement
S Reduce unnecessary movement as prime mover contracts
S Ex: Brachiordialis assists in the flexion of the elbow
Functional Groups
S Fixator
S Synergists that immobilize a bone or muscle origin
S Ex: The muscles of the rotator cuff help stabilize the arm
when it is flexed at the bicep
Muscle actions
S Which muscle is the prime mover and what is the
antagonist:
S Flexion at the elbow?
S Flexion at the knee?
S Extension at the elbow?
S Extension at the knee?