Axial Skeleton Muscles Flashcards
What determines the line of force of a muscle?
the orientation of its fibers
If the line of force is oriented in the horizontal plane, what motion will occur?
rotation
If fibers are parallel to the vertical plane, what motions will they favor?
flex/extend
What two muscles are parallel to the sagittal plane, making them excellent flexor/extendors?
- longissimus thoracis
- rectus abdominus
Can a muscle produce torque if its line of force is parallel to the axis of rotation?
NO
T/F: External oblique favors rotation.
false, actually 86% flexion/extension, and 50% rotation b/c closer to sagittal plane
- not a pure rotator or flex/extender
Does rectus abdominus produce rotation?
no
T/F: Unilateral contraction of abdominal muscles produces pure flexion/extension.
false- must be bilateral contraction to be pure flex/extend, otherwise some side-bending or rotation occurs
T/F: Muscles that produce internal torque for concentric activity also resist external torque eccentrically.
true - trunk extensors eccentrically control flexion
T/F: Axial muscle function is dependent upon degree of fixation.
true - some motion at pelvis, some at spine; just depends what is fixed
If the moment arm is longer, what happens to torque?
longer moment arm = more torque produced
Muscles have different moment arms depending on their length. What is advantageous for a long moment arm, as well as a short moment arm?
- long moment arm = these muscles are great movers
- short moment arm = these muscles are more for stabilization, not as good at moving
What are the actions of the transversospinal muscles?
(interspinalis, rotators, multifidus, levator costarum, intertransversarii)
- do contralateral rotation, ipsilateral side bend, and extension
- but MOSTLY proprioception
T/F: Shorter segmented muscles have fewer muscle spindles than long muscles.
false; they have more spindles, allowing greater proprioception
Which area of the spine has the most highly developed short segmented muscles?
cervical area -> since head is constantly moving, need constant feedback (proprioception), so these muscles are highly developed
Which 2 of the 3 obliques are attached to thoracolumbar fascia, making them good core stabilizers?
obliquus internus and transverse abdominus
- these muscles should fire first for proper core stabilization
Which oblique is capable of contralateral rotation? Which one does internal rotation?
obliquus externus = contralateral
obliquus internus = ipsilateral
Explain the synergy of the internal and external oblique.
- they work in opposites for rotation, but work together on both sides for flexion
What abdominal muscles are working in a right side bend?
R rectus abdominus, R internal oblique, R external oblique, L eccentric control
What abdominal muscles are working in a right rotation?
L external oblique
R internal oblique
no rectus abdominus
What is greater, flexor or extensor torque in the trunk?
extensor = have to resist gravity all the time
- have better fiber orientation and more CSA
When L-spine is stablized, what is the action of the iliopsoas?
flexes the hip, can cause anterior tilt
What muscles are major stabilizers of the low spine?
psoas major and quadratus lumborum
T/F: Rectus capitus lateralis and rectus capitus anterior are important muscles for posture.
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
If this muscle is tight or compressed, it can cause thoracic outlet syndrome.
scalenes: compress brachial plexus or subclavian, getting tingling down arm
What is the primary extensor of the head?
semispinalis capitus
T/F: The longus muscles resist protraction of the head through slight extension.
false, slight flexion
What muscle atrophies before erector spinae, and is thought to contribute to loss of balance?
multifidus
What are the dynamic movers of the posterior craniocervical region? What do they do?
splenius cervicis
splenius capitus
levator scapulae
- bilaterally extend, ips side bend, rotation
What are the stabilizers of the posterior craniocervical region?
suboccipitals, which do capital extension, ips side bend, and rotation
What does increasing your intrabdominal pressure do?
- increase BP
- stabilize spine
To reduce lifting injuries, what the maximum safe amount of weight to lift?
50 lbs (so 764 lbs of compressive force)
Why keep a weight close to you when lifting?
the further out a weight is, the longer the moment arm, which means it requires more force to lift it (bad)
T/F: Joint reaction forces go down when the weight of the object you’re lifting increases.
false, JRF increases as weight increases (bad)
How do backbraces help with lifting?
- 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
What are 6 ways to reduce lifting injury?
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
What happens with the diaphragm, volume of ab cavity, and glottis to increase intra-abdominal pressure?
glottis closes, diaphragm contracts and lowers, decreasing the intra-abdominal volume
- this increases pressure and stabilizes spine below diaphragm
