The shoulder girdle includes the scapula – this bone is involved
in many movements and must be stabilized for others. The
muscles that serve as stabilizers are the trapezius, rhomboids,
levator scapulae, serratus anterior and pectoralis minor.
PROTRACTION
AGONIST: Serratus Anterior
ANTAGONIST: Trapezius &
Rhomboids
SYNERGIST(s): Pectoralis Minor
ELEVATION
AGONIST: Trapezius (upper)
ANTAGONIST: Trapezius (lower)
SYNERGIST(s): Levator Scapulae,
Trapezius (middle)
The SITS muscles comprise what we call the ‘rotator cuff’.
Although involved in rotation of the humerus (& abduction in
the case of the supraspinatus), they are primarily stabilizers of
the shoulder joint, holding the humerus in the glenoid fossa.
One example is internal rotation with the
suscapularis as one of the synergists to the
the latissimus dorsi (agonist).
Another role of synergists is played by the
wrist flexors as they hold a 2nd joint from
moving while the desired action takes
place.
External rotation is achieved by the
posterior deltoid with the infraspinatus,
teres minor & the latissimus dorsi as
synergists. Again, the wrist muscles
(extensors) play the role of stabilizers.
SHOULDER
ADDUCTION
AGONIST:
Latissimus Dorsi
ANTAGONIST:
Lateral Deltoid
SYNERGIST(s):
Pectoralis Major,
Teres Major, Coracobrahialis
NOTE: The scapula must
complete downward rotation
during this movement,
involving the rhomboids
SHOULDER
ABDUCTION
AGONIST:
Lateral Deltoid
ANTAGONIST:
Latissimus Dorsi
SYNERGIST(s):
Supraspinatus
NOTE: The scapula must
complete upward rotation
during this movement,
involving the trapezius &
pectoralis minor muscles
SHOULDER
FLEXION
AGONIST:
Anterior Deltoid
ANTAGONIST:
Posterior Deltoid
SYNERGIST(s):
Biceps Brachii (short head),
Pectoralis Major,
Coracobrachalis
NOTE: Flexion of the
shoulder occurs in the sagittal
plane, around the transverse
axis
SHOULDER
EXTENSION
AGONIST:
Posterior Deltoid
ANTAGONIST:
Anterior Deltoid
Pectoralis Major
SYNERGIST(s):
Latissimus Dorsi, Teres
Major, Triceps Brachii (long
head)
NOTE: Extension of the
shoulder also occurs in the
sagittal plane, around the
transverse axis
ELBOW FLEXION
AGONIST:
Biceps Brachii is
the prime mover.
ANTAGONIST:
Triceps Brachii
SYNERGIST(s):
Brachialis, Brachioradialis,
Pronator Teres
Distal & proximal radio-ulnar joints allow the forearm to
turn in order to do many of the fine motor & sport-related
movements of the hand I.e. Pronation and supination as the
radius rolls over the ulna through the transverse plane
around the longitudinal axis.
SUPINATION is achieved
by the biceps brachii with
the supinator as synergist.
PRONATION is achieved by
the pronator teres &
quadratus together with no
real synergist.
The pelvic girdle includes the pelvic bones– 3
fused bones that stabilize the hip joint for weight
bearing. It is further stabilized by the deep lateral
rotator muscles that play the same role as the
rotator cuff does in the pectoral girdle – synergists
as they stabilize the hip joint and help rotate the
femur
HIP FLEXION
AGONIST:
Iliopsoas is 2 muscles with
powerful origin & insertion
on the lumbar vertebrae,
pelvic bone & greater
trochanter of the femur
NOTES: The only quadricep muscle
that acts on the hip is the rectus
Gluteus Maximus or
femoris; the AGONIST in HIP
Hamstring Group
EXTENSION depends on the
intensity of the action ~ in walking
SYNERGIST(s):
the hamstrings do most of the work;
Rectus Femoris, Sartorius, in running or climbing stairs the
gluteus maximus is the agonist.
Tensor Fasciae Latae
ANTAGONIST:
HIP ABDUCTION
AGONIST:
Gluteus medius
ANTAGONIST:
Adductor Group
SYNERGIST(s):
Tensor Fasciae Latae,
Gluteus Minimus
NOTE: Abduction & adduction
occur through the frontal plane,
around the AP axis
KNEE FLEXION
AGONIST: HAMSTRINGS
Semimembranosus,
Semitendinosus, Biceps
Femoris
ANTAGONIST: QUADRICEPS
Rectus Femoris, Vastus Lateralis,
Vastus Intermedius, Vastus Medialis
SYNERGIST(s):
Gastrocnemius, gracilis,
sartorius
NOTE: In the opposing action
(knee extension) the only
muscle(s) doing the action is the
quad group. There is no synergist.
PLANTAR FLEXION
AGONIST:
Gastrocnemius
ANTAGONIST:
Tibialis Anterior
SYNERGIST(s):
Tibialis Posterior, soleus
NOTE: What looks like extension
of the ankle is plantar flexion ~
moving the toes & knees closer is
dorsi-flexion, with the Tibialis
Anterior as AGONIST.