the maximal internal torque potential is equal to the product of (1) the muscle force generated parallel to a plane and, (2) the length of the internal moment arm available to the muscle
Spatial orientation of a muscle's line of force determines...
its effectiveness for producing an action
Horizontal vs Vertical forces
For a muscle to contribute all its force potential toward axial oration, its overall line of force must be directed solely in the horizontal direction.
For a muscle to contribute all its force potential toward either lateral flexion or flexion, its overall line of force must directed verticallyFor all force potential, line of force must be in that plane
More of the total muscle mass of the trunk is biased vertically than horizontally.
Activation within the axial skeleton
Bilateral: usually produces pure flexion or extension of the axial skeleton
Unilateral: tends to produce flexion or extension of the axial skeleton
The action of a muscle within the axial skeleton depends on...
the relative degree of fixation or stabilization of the attachments of the muscle
axial skeleton assumed _____ end less contrained and moves over ____ end
Influence of Gravity. Action of muscle is ____, rotating body against gravity or some other external resistance
Muscles of Posterior Trunk - Superifical
Muscles of Posterior Trunk - intermediate
serratus posterior superior
serratus posterior inferior
Muscles of Posterior Trunk - deep
From superficial to deep, the deep muscles fiber length progressively gets..
- spinalis - lumborum, thoracis, cervicis
- longissimus - thoracis, cervicis, capitis
- iliocostalis - thoracis, cervicis, capitis
**has a common tendon that anchors it to the axial skeleton by several direct or indirect attachments
The erector spinal muscles cross a considerable distance along the axial skeleton. This anatomic feature suggests a design more suited for control of ___ movements of the entire axial skeleton that for control of ___ movements at individual intervertebral junctions.
Erector spinae - bilateral vs unilateral contraction
bilateral contraction: extends trunk, neck, or head, can APT, accentuate lumbar lordosis (iliacus taut), or both