Muscular joint actions
Spine
Concentric contraction Eccentric contraction
To rotate spine toward front leg:
Erector spinae, internal oblique (front leg
side); transversospinalis, rotatores, external
oblique (back leg side)
To resist flexion caused by action of arms:
Spinal extensors
To balance rotation around axis:
Transversospinalis, rotatores, external oblique
(front leg side); erector spinae, internal
oblique (back leg side)
Upper limbs
Concentric contraction
Eccentric contraction
or passively lengthening
To stabilize humeral head:
Rotator cuff
To internally rotate shoulder and prevent
protraction:
Subscapularis, anterior deltoid
To extend arm back:
Teres major, posterior deltoid, latissimus dorsi
To extend shoulder and elbow:
Triceps brachii
To grasp:
Flexors of fingers and hand
Upper trapezius, pectoralis major and minor,
serratus anterior, coracobrachialis
Lower limbs
Front leg Back leg
Concentric
contraction
Eccentric
contraction
Concentric
contraction
Passively
lengthening
To resist tendency
to widen knee
(abduct at hip):
Gracilis, adduc-
tor longus and
brevis
To allow hip and knee
flexion and ankle dor-
siflexion without col-
lapsing into gravity:
Gluteus maximus, ham-
strings at hip joint,
vastii, soleus, intrinsic
and extrinsic muscles
of foot
To level and center
pelvis over feet and to
maintain balance side
to side (the narrower
the stance, the more
active and long these
muscles need to be):
Gluteus medius and
minimus, piriformis,
superior and inferior
gemellus
To extend hip:
Hamstrings at hip joint,
gluteus medius (pos-
terior fibers), adduc-
tor magnus, gluteus
maximus
To extend knee:
Articularis genu, vastii
Soleus, gastrocne-
mius
(continued)