Important Muscle Terminology
Skeletal muscles connect from one bone to another and cross at least one joint.
Muscle contraction causes tension which results in movement by pulling the bones toward each other.
Muscles generate torque which results in angular motion at the joint.
Action – what movement does the muscle cause? Examples would include flexion, extension, abduction,
adduction, circumduction, etc.
Agonist – muscle primarily responsible for the movement
Antagonist – muscle that resists the movement. Provides joint integrity
Synergist – muscle that assists the agonist in carrying out the movement
Neutralizer, fixator, or stabilizer – muscle that prevents unwanted body movement
Origin – tendon attachment site for a muscle that is located more medially or more stationary. Some
muscles have more than one origin.
Insertion – tendon attachment site for a muscle that is located more distally or more moveable. Some
muscles have more than one insertion.
Single joint muscle – muscle that crosses only one joint.
Two joint muscle – muscle that crosses two joints.
Muscle Shapes:
a. Pennate – feather shaped; unipennate, bipennate, multi-pennate (quadriceps femoris)
b. Parallel – long, strap-like muscles (Sartorius and Rectus Abdominis)
c. Convergent – fibers converge at insertion; fan shaped (Deltoid)
d. Circular – located surrounding an opening (eye and mouth)
Naming of Muscles:
a. Shape – trapezoid, rhomboid, quadrates
b. Location – pectoralis (chest)
c. Size – minimus, maximus, longus, brevis
d. Origin and Insertion – brachioradialis, sternocleidomastoid
e. Number of heads – biceps, triceps
f. Function – adductor, abductor, flexor, extensor