Laura Spenceley
Task 2 – Muscle Movements & Terms
A&P
Muscle Movement Terminology
AGONIST / PRIME MOVER The term agonist refers to the muscle that is primarily responsible for a specific joint motion, or the
muscle that is directly involved in a contraction. For an agonist to be effective as a mover in the
skeletal system, it must actually cross one or more structure(s) that can move. This is typically where
the muscle crosses a joint by way of a connecting tendon. As the myofibrils of a muscle are excited
into action and then contract, they will create tension and pull through the tendon and pull the lever
arm of bone on the opposite side of the joint closer to the muscle's origin.
ANTAGONIST –
The antagonist in a movement refers to the muscles that oppose the agonist. During elbow flexion
where the bicep is the agonist, the tricep muscle is the antagonist. While the agonist contracts
causing the movement to occur, the antagonist typically relaxes so as not to impede the agonist. The
antagonist doesn’t always relax though, another function of antagonist muscles can be to slow down
or stop a movement. We would see this if the weight involved in the bicep curl was very heavy,
when the weight was being lowered from the top position the antagonist tricep muscle would
produce a sufficient amount of tension to help control the movement as the weight lowers.
This helps to ensure that gravity doesn’t accelerate the movement causing damage to the elbow
joint at the bottom of the movement. The tricep becomes the agonist and the bicep the antagonist
when the elbow extends against gravity such as in a push up, a bench press or a tricep pushdown.
SYNERGISTThe synergist in a movement is the muscle(s) that stabilises a joint around which movement is
occurring, which in turn helps the agonist function effectively. Synergist muscles also help to create
the movement. In the bicep curl the synergist muscles are the brachioradialis and brachialis which
assist the biceps to create the movement and stabilise the elbow joint.
FIXATORThe fixator in a movement is the muscle(s) that stabilises the origin of the agonist and the joint that
the origin spans (moves over) in order to help the agonist function most effectively. In the bicep curl
this would be the rotator cuff muscles, the ‘guardians of the shoulder joint’. The majority of fixator
muscles are found working around the hip and shoulder joints.
Laura Spenceley
Task 2 – Muscle Movements & Terms
A&P
EXAMPLES IN SPORT - ROWING
Rowing is a coordinated muscle action that involves every large muscle group in the body. A basic
rowing stroke is split up into four key phases; the catch, the drive, the finish and the recovery. The
following sections illustrate the primary muscles used during each movement of the rowing stroke
and which muscles are acting as the agonist, antagonist, fixator and synergist.
1. The Catch
In this position your legs are compressed and
shins vertical. Your triceps contract as the agonist
to extend your arm whilst the bicep muscles work
as antagonists relaxing to oppose the tricep
movement. Your back muscles are relaxed, and
your abdominals are flexing your torso forward.
2. The drive
You initiate the drive with the powerful muscles of your
legs, and all of the shoulder muscles are contracting. As
you work through the drive sequence, your biceps
engage to pull the handle toward your abdomen, your
back muscles work more as you swing your torso open,
and your glutes and hamstrings contract to extend the hip. As the
drive finishes with the arm pull-through, nearly all the muscles of
your upper body engage.
3. The finish
At the finish, the abdominals stabilize the body, and
the glutes and quads are contracting. The biceps and
many of the back muscles are also contracting to
help keep the torso in the finish position and to
internally rotate the upper arms.
4. The Recovery
The triceps engage to push the arms forward and away from
the body. The abdominals flex the torso forward, and the
hamstrings and calves contract as you slide up to the catch.
Laura Spenceley
Task 2 – Muscle Movements & Terms
A&P