Axial Skeleton Muscles

Question 1

What determines the line of force of a muscle?

Answer 1

the orientation of its fibers

Question 2

If the line of force is oriented in the horizontal plane, what motion will occur?

Answer 2

rotation

Question 3

If fibers are parallel to the vertical plane, what motions will they favor?

Answer 3

flex/extend

Question 4

What two muscles are parallel to the sagittal plane, making them excellent flexor/extendors?

Answer 4

• longissimus thoracis

- rectus abdominus

Question 5

Can a muscle produce torque if its line of force is parallel to the axis of rotation?

Answer 5

NO

Question 6

T/F: External oblique favors rotation.

Answer 6

false, actually 86% flexion/extension, and 50% rotation b/c closer to sagittal plane
- not a pure rotator or flex/extender

Question 7

Does rectus abdominus produce rotation?

Answer 7

no

Question 8

T/F: Unilateral contraction of abdominal muscles produces pure flexion/extension.

Answer 8

false- must be bilateral contraction to be pure flex/extend, otherwise some side-bending or rotation occurs

Question 9

T/F: Muscles that produce internal torque for concentric activity also resist external torque eccentrically.

Answer 9

true - trunk extensors eccentrically control flexion

Question 10

T/F: Axial muscle function is dependent upon degree of fixation.

Answer 10

true - some motion at pelvis, some at spine; just depends what is fixed

Question 11

If the moment arm is longer, what happens to torque?

Answer 11

longer moment arm = more torque produced

Question 12

Muscles have different moment arms depending on their length. What is advantageous for a long moment arm, as well as a short moment arm?

Answer 12

• long moment arm = these muscles are great movers

- short moment arm = these muscles are more for stabilization, not as good at moving

Question 13

What are the actions of the transversospinal muscles?

Answer 13

(interspinalis, rotators, multifidus, levator costarum, intertransversarii)

• do contralateral rotation, ipsilateral side bend, and extension
• but MOSTLY proprioception

Question 14

T/F: Shorter segmented muscles have fewer muscle spindles than long muscles.

Answer 14

false; they have more spindles, allowing greater proprioception

Question 15

Which area of the spine has the most highly developed short segmented muscles?

Answer 15

cervical area -> since head is constantly moving, need constant feedback (proprioception), so these muscles are highly developed

Question 16

Which 2 of the 3 obliques are attached to thoracolumbar fascia, making them good core stabilizers?

Answer 16

obliquus internus and transverse abdominus

- these muscles should fire first for proper core stabilization

Question 17

Which oblique is capable of contralateral rotation? Which one does internal rotation?

Answer 17

obliquus externus = contralateral

obliquus internus = ipsilateral

Question 18

Explain the synergy of the internal and external oblique.

Answer 18

• they work in opposites for rotation, but work together on both sides for flexion

Question 19

What abdominal muscles are working in a right side bend?

Answer 19

R rectus abdominus, R internal oblique, R external oblique, L eccentric control

Question 20

What abdominal muscles are working in a right rotation?

Answer 20

L external oblique
R internal oblique
no rectus abdominus

Question 21

What is greater, flexor or extensor torque in the trunk?

Answer 21

extensor = have to resist gravity all the time

- have better fiber orientation and more CSA

Question 22

When L-spine is stablized, what is the action of the iliopsoas?

Answer 22

flexes the hip, can cause anterior tilt

Question 23

What muscles are major stabilizers of the low spine?

Answer 23

psoas major and quadratus lumborum

Question 24

T/F: Rectus capitus lateralis and rectus capitus anterior are important muscles for posture.

Answer 24

false, they’re really too small to be movers into good posture, more for stabilization
- the muscles that really are good are longus capitus and colli

Question 25

If this muscle is tight or compressed, it can cause thoracic outlet syndrome.

Answer 25

scalenes: compress brachial plexus or subclavian, getting tingling down arm

Question 26

What is the primary extensor of the head?

Answer 26

semispinalis capitus

Question 27

T/F: The longus muscles resist protraction of the head through slight extension.

Answer 27

false, slight flexion

Question 28

What muscle atrophies before erector spinae, and is thought to contribute to loss of balance?

Answer 28

multifidus

Question 29

What are the dynamic movers of the posterior craniocervical region? What do they do?

Answer 29

splenius cervicis
splenius capitus
levator scapulae
- bilaterally extend, ips side bend, rotation

Question 30

What are the stabilizers of the posterior craniocervical region?

Answer 30

suboccipitals, which do capital extension, ips side bend, and rotation

Question 31

What does increasing your intrabdominal pressure do?

Answer 31

• increase BP

- stabilize spine

Question 32

To reduce lifting injuries, what the maximum safe amount of weight to lift?

Answer 32

50 lbs (so 764 lbs of compressive force)

Question 33

Why keep a weight close to you when lifting?

Answer 33

the further out a weight is, the longer the moment arm, which means it requires more force to lift it (bad)

Question 34

T/F: Joint reaction forces go down when the weight of the object you’re lifting increases.

Answer 34

false, JRF increases as weight increases (bad)

Question 35

How do backbraces help with lifting?

Answer 35

• They give the wearer proprioception to remind them to contract abs, and they give some slight stabilization
• but people can rely on them, and that gets bad b/c then you’ll only contract abs with the brace on

Question 36

What are 6 ways to reduce lifting injury?

Answer 36

1) keep weight close to body
2) bend your knees, bringing body closer to weight and reducing moment arm
3) no twisting
4) lift slowly
5) keep weight centered
6) reduce weight
7) ask for help if needed

Question 37

What happens with the diaphragm, volume of ab cavity, and glottis to increase intra-abdominal pressure?

Answer 37

glottis closes, diaphragm contracts and lowers, decreasing the intra-abdominal volume
- this increases pressure and stabilizes spine below diaphragm