WEEK FOUR: Spinal mechanics and posture Flashcards
1
Q
Is posture a dynamic process?
A
Yes
2
Q
Explain centre of gravity
A
- Centre point where all of our mass is distributed.
- Maintain centre of gravity in an area within or over the base of support
- Segments above the base can be adjusted to bring the body back into balance
3
Q
Explain the base of support
A
- Area defined by feet (width)
- Walking sticks and walking frames become base of support.
- Walking aids increase the area of the base of support
4
Q
Explain the line of gravity
A
- Imaginary line that extends from the CoG to the ground.
- AKA centre of gravity projection
5
Q
Where is the centre of gravity in the anatomical position?
A
- S2, just behind the belly button.
- Differs slightly between each person
6
Q
Explain where the centre of gravity is when we move forward?
A
- CoG will move in front of body (outside body). Projection goes in front of feet
- Less stable.
- Muscles need to work harder to maintain position because more movement
7
Q
In an idealised posture, the Line of Gravity drops in the middle between what bilateral points?
A
- The mastoid processes (pressure point behind ears)
- A point anterior to the shoulder joints
- A point posterior to the hip joints
- A point anterior to the knee joints
- A point anterior to the ankle joints
8
Q
What makes the idealised posture ‘ideal’?
A
- Minimal energy and muscle contraction required to maintain posture (equilibrium)
- Protects supporting structures against injuries and progressive deformity
- Optimal for thoracic and abdominal organs
9
Q
What role do the muscles play in posture?
A
- All of the muscles constantly adjust to maintain equilibrium
10
Q
What are the factors contributing to static balance?
A
- The muscles activated in static balance forming the postural tone to keep body from collapsing in response to the pull of gravity
- So the motor control and strength of these muscles
11
Q
Explain postural sway
A
- No posture is absolutely static, constant sway around any chosen position
- ## Inverted pendulum theory: Lots of mass on top, base at bottom. Mass sways around fixed point on ground
12
Q
Can measuring the postural sway help to diagnose neurological disorders?
A
Yes
13
Q
What is our postural sway affected by?
A
The position of other parts of the body.
If put hands in front = greater postural sway
14
Q
Name 3 out of the 6 factors that affect posture and compensatory change?
A
- Emotion
- Forces applied by body structures (muscles, ligaments)
- Forces applied by gravity, wind or other external forces
15
Q
Name the rest of the 6 factors that affect posture and compensatory change?
A
- Mechanics of joint and lever systems
- Extraneous factors: Pain, pregnancy, obesity, holding a heavy box
- Changes in positions of specific joints and regions: Result in compensatory changes to the positions of other joints or regions
16
Q
Explain the concept of balance. When is it affected?
A
- The ability to maintain posture
- Balance is affected when line of gravity moves outside of the base of support.
- Means we are more mobile but also have the potential to loose balance
17
Q
Explain what happens with our balance when we go from sitting to standing
A
- Decrease base of support
- Centre of gravity also increases in height.
- Decreases stability but increases mobility
18
Q
Explain what happens with our balance when we go from standing to walking
A
- Unsteady base of support because it’s always changing
- CoG is always moving and always moving forward
- For balance, we have to fall over our BoS
- Controlled falling: As CoG moves forward to compensate, BoS also moves
19
Q
What does postural awareness rely heavily on?
A
- Sensory feedback
- Vision, vestibular system and somatosensory info.
20
Q
Explain vision in terms of postural awareness
A
- For reference system/point of where everything is around us and in relation to us
- Most important one
21
Q
Explain the vestibular system in terms of postural awareness
A
- Info in ears. Fluid with senses in it that tell us where our head is in relation to our body
22
Q
Explain the somatosensory info in terms of postural awareness
A
- Info. from joint, muscle and skin receptors.
- Proprioception
23
Q
Explain the four main causes of abnormal posture
A
- Pathology (injury) of joints, muscles, NS
- Lack of, or distorted awareness of body position
- The learning over a long period of a particular abnormality, such that it becomes the norm. Positive feedback
- Asymmetries or imbalances of forces acting on specific joints or regions in “non-optimal” postures must be compensated for by asymemtries/imbalances etc.
24
Q
Name the three most common abnormal postures
A
- Kyphosis
- Lordosis
- Scholiosis
25
Explain Kyphosis
- An exaggerated curve in the thoracic region (slumped)
- Common in older people (intervertebral discs degenerate) and sitting jobs (something too far away or too far in front of them).
- Flexion
- Sagittal plane
26
Explain Lordosis
- When pregnant & obesity. Tight muscles (erector spinae)
- Exaggerated lumbar spine curve.
- Hyper lordotic position
- More mass anteriorly, compensate by leaning back. Change CoG.
- Sagittal plane
27
Explain Scholiosis
- Leg length inequality
- Can have it at any region of the spine
- S is in frontal plane
28
What are the 4 forces on the lumbar spine?
- Disc sheer force
- Disc compressive force
- Erector spinae force
- Moment due to applied load
29
Why are the intervertebral discs particularly important? Why are they particularly prone?
- Important for integrity of spine
| - Particularly prone because much more force going through it
30
What happens when we load up the body?
- Because forces going through the lumbar area, contractions from muscles (erector spinae) to compensate to maintain posture and balance.
- Contractions compress discs and are under a lot of force
31
What main force occurs during flexion?
- Sheer force, discs want to move out
32
Where do discs most commonly herniate?
- Most commonly around the lumbar spine because discs are bigger
- Will herniate posterior laterally during flexion
33
Explain the concept of why you're taller in the morning?
- Because discs are on constant load during the day, fluid in middle slowly seeps out into outer space around disc.
34
Does sitting or standing create more pressure on the discs?
Sitting
35
Why should you not lift at arms length?
Centre of gravity is further away from base of support, more work for muscles to maintain posture
36
Why should you not keep your legs straight when lifting?
- causes shearing and compression force
37
What should you remember when lifting heavy objects and why?
- Keep load close to body to keep CoG low and over base of support
- Squat down to lower CoG and increase stability
38
Describe the concept of viscoelastic creep?
- If stretch passive structures such as discs and ligaments over along period of time, then get reset to become longer.
- Occurs when: Holding flexed positions. Mainly for ligaments that run down back
- No longer useful at maintaining stability of spine. Rely much more on muscles, will get back pain
39
Why is it called a viscoelastic creep?
- Have visco (fluid) elastic type properties
| - Creep: Ligament gets longer and longer
40
What is muscle coactivation?
| Where do we want this especially?
- Where both the agonist and antagonist are activated at the same time.
- Want it in the trunk to stay in posture/position
41
Explain the concept of intra-abdominal pressure?
| Why do we want this pressure?
- Increase intra-abdominal pressure to get coactivation by by embracing the spine.
- Want this pressure to increase the stability of the spine
42
What is abdominal bracing and why do we use it?
- Uses the transverse abdominis
| - Stiffens like a corset around the spine to offer protection and increase stability
43
Does abdominal bracing cause an increase in blood pressure?
No
44
Why is the pelvic tilt important?
Can change position of lumbar spine and can be implicated in back pain
45
What are the 5 major muscle groups that align the pelvis?
- Rectus abdominis
- Iliopsoas
- Rectus femoris
- Hamstrings
- Gluteals
46
Does the anterior pelvic tilt increase or decrease lumbar lordosis? What does this mean?
- Increases lumbar lordosis.
| - Extends lumbar spine
47
What occurs if the anterior pelvic tilt is maintained?
- Back extensors and hip flexors loose flexibility or become tight.
- Hamstrings and abdominals become lax/loose and weak
48
Does the posterior pelvic tilt increase or decrease lumbar lordosis? What does this mean?
- Decreases lumbar lordosis
| - Slumped, starts to straighten spine
49
What occurs if the posterior pelvic tilt is maintained?
- Hip flexors and lower back muscles become lax/loose, weak.
| - Abdominals and hamstrings become tight
50
What is the anterior pelvic tilt corrected by?
- Strengthening hip extensors and abdominals. Stretching the lower back and hip flexors.
51
What is the posterior pelvic tilt corrected by?
- Strengthening back extensors and hip flexors. Stretching the hip extensors.
52
Why do the hamstrings have a major effect on the configurations of the spine and pelvis?
- Because they cross both the hip and knee joints.
53
What is the aponeurosis?
- A flat sheet of connective tissue used for muscle insertion
54
Muscles of the vertebral system are simple, having only one superior and inferior attachment. True or false?
- False
55
The internal oblique abdominal inserts on the:
- costal cartilage of the 8th, 9th and 10th ribs and linea alba
56
The sternocleidomastoid has it's superior attachment where?
- On the mastoid processes
57
What is the linea alba?
- A narrow, vertical, fibrous strip used to attach muscle sheaths of the left and right rectus abdominis
58
What depresses the rib?
- Internal intercostals
- Serratus posterior inferior
- transversus thoracis
59
What part of the IV disc is thicker?
- The anterior part is thicker than the posterior.
60
From C7 onwards, the ligamentum nuchae is formed as a continuation of which ligament?
The supraspinous ligament
61
What are the functions of the anterior and posterior ligaments? What movements would these ligaments restrict?
Anterior: To stabilise and prevent movement. Stop excessive extension
Posterior: Reinforce the intervertebral discs. Stop excessive flexion
62
What is the function of the iliopsoas
Flexes the hip
63
How do the muscles of the abdominal wall work with the back muscles in bending forwards, backwards and side to side?
Stabilise and create compression to support spine.
