Ch 10: axial skeleton - muscle and joint

Actions of the trapezius

All: scapular retraction. Upper/lower: upward rotation. Upper: elevation. Lower: depression

Actions of lats

GH adduction, extension, internal rotation, horizontal adduction

Actions of Rhomboids

scapular retraction, elevation, downward rotation

Actions of levator scapulae

scapular elevation

Actions of serratus anterior

scapular protraction, upward rotation

True or False: the erector spinae group is responsible for gross movements of the spine

true: the ES group crosses many segments of the spine

What movment does bilateral contraction of the erector spinae group produce?

trunk, neck, and head extension, anterior pelvic tilt

What movement does unilateral contraction of the erector spinae produce?

iliocostalis is most effective lateral flexor, longissimus and iliocostalis ipsilaterally rotates the head and neck

Which erector spinae muscle has the largest internal moment arm?

iliocostalis because it is furthest away from the spine

True or False: the transversospinal muscles are responsible for gross movements of the spine?

False: they do not cross as many segments, leading to more controlled movements and functional stabilization

What muscles are included in the transversospinal group?

semispinalis, multifidi, rotatores

What is the bilateral action of the transversospinal muscles?

extension

What is the unilateral actions of the transversospinal muscles

lateral flexion, contralateral rotation

What muscles are included in the short segmental group?

interspinalis and intertransversarius

Why is the short segmental group responsible for fine motor control of the axial skeleton?

highly segment, each individual muscle crosses one IV junction, high density of muscle spindles = better proprioception

What is the bilateral action of the short segmental group?

extension

What is the unilateral action of the intertransversarius?

lateral flexion

What are the muscles of the anterior lateral trunk?

rectus abdominis, external obliques, internal obliques, transversus abdominis

Which abdominal muscle has the smallest cross sectional area?

rectus abdominis

Which abdominal muscle has the largest cross sectional area?

internal obliques

What is the bilateral action of the rectus abdominis, external/internal oblique?

reduce the distance between xiphoid and pubis symphysis in order to produce trunk flexion or posterior pelvic tilt

What is the unilateral action of the rectus abdominis, external/internal oblique?

lateral flexion and rotation

If the trunk rotates to the right, which oblique is responsible for ipsilateral rotation?

internal oblique

Actions of the iliopsoas?

hip flexion and anterior pelvic tilt

Bilateral action of quadratus lumborum?

extension of lumbar spine

unilateral action of quadratus lumborum?

lateral flexion of lumbar spine

What are intrinsic core stabilizers?

short, deep, segmented muscles

What are extrinsic core stabilizers?

longer attachments outside of vertebral column

Examples of intrinsic trunk stabilizers?

transversospinal group, short segmental group

Examples of extrinsic trunk stabilizers?

erector spinae, quadratus lumborum, abdominals, psoas

Describe the movement of the trunk and hip during a standard sit up

abdominal muscles flex trunk while also posteriorly tilting pelvis. biceps femoris eccentrically activated due to hip flexion

Explain the significance of the stabilizing function of the abdominals and lumbar multifidi

abdominal muscles often activate before other actions due to anticipatory and subconscious feedforward mechanisms (transversus abdominus and internal oblique activate before the deltoid with shoulder flexion)

Explain the relationship between chronic low back pain and core activation

some evidence shows a delay in transversus abdominus activation, or an overactivation leading to fatigue

List the muscles of the craniocervical region

SCM, scalenes, longus colli/capitis, rectus capitis, splenius cervicis/capitis, suboccipitals

What are some causes of chronic forward head posture?

hyperextension injury of craniocervical muscles leading to guarding, pain/weakness of deep neck flexors, poor ergonomics

True or false: lifting heavy objects generates large compression, tension, and shear forces

true, especially in lumbopelvic region

True or false: the extensor muscle moment arm is relatively large and gives a mechanical advantage relative to external loads

False: the extensor moment arm is relatively small and gives a mechanical disadvantage relative to external loads

Which of these is NOT a way to reduce force demands on back muscles while lifting?

increasing the rate of lifting

What is the most effective way to reduce the force demands on back muscles while lifting?

reduce the length of external moment arm of external load (i.e. lift the load between the knees)

How can you increase the moment arm of the low back extensors?

increase lumbar lordosis

Which of these is considered a safe lifting technique?

lift with a moderately wide and slightly staggered BOS

How does the valsalva maneuver reduce demands on the lumbar extensors during lifting?

creates modest extension torque, lowering muscular based compression forces

which abdominal muscle is responsible for the “corset effect”?

transversus abdominis due to horizontal attachments into thoracolumbar fascia

True or false: the stoop lift is safer than the squat lift

false: both are biomechanical extremes, but the squat lift has less stress on the low back

Describe the stoop lift

extending the hips and lumbar region while knees are slightly flexed

Describe the squat lift

knees are maximally flexed, hips and knees extend during the lift

True or false: the stoop lift is more metabolically efficient

true: stoop is 20-30% more metabolically efficient due to less body mass being moved through space

Which squat technique is most effective for the real world?

a freestyle combination between stoop and squat

Which abdominal muscles are responsible for feedforward control?

transversus abdominus, internal oblique, external oblique

how does the contact area and pressure change with trunk flexion?

decreased contact area, increased pressure

how does the contact area and pressure change with trunk extension?

increased contact area, decreased pressure

What are the three component parts of the interbody joint?

IV disc, vertebral body, end plates

Why is the annulous fibrosus susceptible to injury?

due to the orientation of the fibers

What ligament is responsible for limited flexion torque in the thoracolumbar region?

supraspinous ligament

What percentage of body weight runs through the interbody joints and posterior element while standing?

80 percent interbody, 20 percent posterior element

The ligamentum nuchae arises from which ligament?

supraspinous ligament

What is the closed pack position of the SI joint

posterior pelvic tilt/ sacral nutation

In which direction does the sacrum move during nutation?

anteriorly

In which direction does the pelvis move during nutation?

posteriorly

Which of the following ligaments is NOT tensioned during nutation?

long posterior SI ligament

In which direction does the sacrum move during counter-nutation?

posteriorly

In which direction does the pelvis move during counter-nutation?

anteriorly

Which of the following is anterior tilt associated with?

narrowing the IV foramen

Which of the following is posterior tilt associated with?

shifting the nucleus proprious posteriorly

Which muscles are involved with the valsalva maneuver?

abdominals, pelvic floor, diaphragm