Balance & Posture Flashcards
1
Q
Define «center of gravity»
A
Point of application of the resultant of the gravitation forces
2
Q
Where is Center of gravity located in anatomical stance ?
A
Anterior between S1 and S2
3
Q
Define the Center of mass
A
The theorical point in which the mass of the body is uniformly distributed
4
Q
Define «base of support»
A
The area beneath a person that include every point of contact that the person makes with the supporting surface. It can include body parts and also walking aids or furniture (ex: chair)
5
Q
What are the disadvantages of bipedal posture ?
A
- increase heart work
- increase stress on vertebral column, pelvis and lower extremities
- reduces stability
6
Q
Define good posture
A
A stereotipycal alignement of body limb segment that requires the least effort to maintain and puts the least strain on ligaments, bones and joints.
7
Q
Define static posture
A
The body and its segments are aligned and maintained in a certain posture.
How you hold yourself when you are not moving.
8
Q
Dynamic posture
A
Posture in which the body and its segments are moving.
How you hold yourself when you are moving.
9
Q
Describe the path of the line of gravity in a ideal posture along the sagittal plane
A
- mastoid process of the temporal bone
- anterior to S1
- slightly posterior the the hip joint
- anterior to the knee and ankle
10
Q
Describe the path of the line of gravity in an ideal posture in the frontal plane
A
- through the 2 feet
- through the umbilicus
- through the xiphoïde process
- through the chin and noise
- between the eyes
11
Q
Name the «anti-gravity» muscles
A
Also called postural muscles
- calf muscles + soleus
- hamstrings
- gluteus
- erector spinae
- neck muscles
- cervical muscles
- abdominal and deep hip muscles
- knee extensors, quadriceps femoris
12
Q
What are the types of standing posture
A
- lordosis
- kyphosis
- flat back
- sway back
- scoliosis
13
Q
Describe the body segments alignement in lordosis
A
- pelvis is anteriorly twisted with an increased lumbar lordosis
- knees are hyperextended
- ankle joints are slightly plantar flexing
14
Q
Which muscles are commonly elongated and weak in lordosis ?
A
- anterior abdominals
- lower and middle trapezius
- hamstrings (compensate)
- small muscles of lumbar spine like rotators or multifidus
- upper thoracic and cervical erector spinae
- rhomboids
- hyoid muscles
15
Q
Which muscles are short and strong in lordosis ?
A
- lumbar erector spinae
- hip flexors
- sternocleomastoid
- scalenes
- upper trapezius
- pectoralis major and minor
- subocciptials
- levatore scapulae
16
Q
Describe the body segments alignement in kyphosis posture
A
- head held forward with cervical spine hyperextended : it is the most anteriorly placed body segment
- scapula may be protracted
- inscreased thoracic kyphosis
- hips flexed
- knee hyper extended
17
Q
Which muscles are elongated and weak in kyphosis ?
A
- neck flexors
- upper erector spinae
- if shoulder protracted : middle and lower trapezius
- external obliques
- thoracic erector spinae
- rhomboids
18
Q
Which are the commonly short and strong muscles in kyphosis
A
- neck extensors
- hip flexors
- if scapula protracted : serratus anterior, upper trapezius, pectoralis major and minor, levatore scapulae
- upper abdominal muscles
- intercostalis
19
Q
Describe the body segments position in sway back
A
- the pelvis is the most anterior body segment
- lower lumbar area flattened
- pelvis neutral or in posterior tilt
- hip and knee joint hyperextended
- subject can stand on one leg so the pelvis is tilted down to non-favor side
- favored leg appears longer in stance
20
Q
Name the muscles commonly weak and elongated in sway back
A
- one joint hip flexors
- external obliques
- lower thoracic extensors
- lower abdominals
- neck flexors
- where one leg is favored, gluteus medius, on the favored side
21
Q
What are the muscles commonly short and strong in sway back ?
A
- hamstrings
- hip extensors
- upper fibers of internal obliques
- internal intercostals
- low back musculature is short but not strong
- where one leg is strong TFL and illiotibial tract
22
Q
Describe the body segments in flat back posture
A
- loss of lordosis in the low back with pelvis posterior tilt
- hip and knee joints hyperextended
- forward head posture with increased flexion of thoracic spine
23
Q
Which muscles are elongated and weak in flat back posture ?
A
- one joint hip flexor
- lumbar extensors
- local stabilizers (multifidus, rotatores)
- anterior intercostals
- scapular retractors (?)
24
Q
What are the muscles commonly short and strong in flat back posture
A
- hamstrings
- abdominals
- hip extensors
- scapular retractors
- thoracic erector spinae
25
Describe the body segments alignement in scoliosis
- the spine is curved to left or right (one curve or several curves to left and right)
- ribs protrude on one side and depress on the other side
- pelvis is tilted laterally
- on concavity side : leg looks longer and shoulder drops
26
Which muscles are elongated and weak in scoliosis ?
- muscles on the convex side
- hip abductors on concave side
- foot pronator muslces on the « long side »
27
Which muscles are short and strong in scoliosis ?
- muscles on the concave side
- hip adductors on the convex side
- foot supinator on short side
28
Define balance
- happens when weight is equally spread so you don’t fall
- the ability to move or to remain a position without loosing control or falling
- postural control
- variation of leg muscles length induced by rotation around the ankle joint
29
Define equilibrium
When opposing forces or actions are balanced so that one is not stronger than the other
30
According to the systems model of balance what coincides with stability ?
1) goal / task orientation
2) central set
3) environmental organization
4) sensory organization
5) motor coordination
6) musculoskeletal systems
31
Explain goal/task orientation ?
- what is the nature of the activity or task ?
| - what are the goals or objectives ?
32
Explain central set
The readiness of central nervous system for an upcoming event based on initial conditions, prior experiences and expectations.
Continuous adaptation to optimize the action to peculiar conditions.
33
Define automatic postural responses
The postural strategies and postural synergies
34
On which parameters are the automatic postural responses dependent ?
- the goal of maintaining equilibrium (and not stereotyped reflex)
- depend on the central set : so that they are specific to the conditions of support and adapt to prior experience
35
Explain motor coordination
Precise behavioral and kinematics descriptions of equilibrium reactions exist for various conditions.
Typical responses of standing subjects to surface perturbations
—> postural strategies
—> postural synergies
36
What are the broad categories of postural strategies to maintain/restore balance ?
- ankle and hip strategies
| - stepping and reaching strategies
37
Explain the ankle and hip strategies
- fixed support strategies that return the body center of over the base of support
38
Explain the stepping and reaching strategies in broad
- change in support strategies : strategies that change the base of support under the falling center of mass
39
Describe the ankle strategy to maintain balance
- the body moves as a flexible inverted pendulum
- the muscles are recruited distal to proximal
- head movement is in phase with the hips
It is used when there is a slow, low amplitude perturbation and when the contact surface is firm, wide and longer than the foot.
40
Describe the hip strategy to maintain balance
- the body exerts torque at the hips in order to quickly move its center of mass
- muscles are recruited proximal to distal
- head movement is out of phase with hips movement
Used when the perturbation is sudden or with a large amplitude and/or the surface is unstable or shorter than the feet
41
Explain the gradual adaptation of strategy to maintain balance
Gradual adaptation from an ankle to a hip strategy (and vice a versa) due to change in surface between large and narrow
42
Describe the stepping strategy to maintain balance
- used to prevent fall
- first attempt is to replace the body center of mass to initial position by exerting ankle torque
- used when perturbations are sudden, with large amplitude or when other strategies fail
43
Explain the reaching strategy to maintain balance
- used to prevent a fall if a rail or a stable support is present
- faster than stepping strategy
- forward bend of the trunk with flexion of the ankle and hips which may progress to a squat
- the center of gravity is lowered
44
Describe musculoskeletal system (with regard to systems model stability)
- range of motion of joints
- strength / power
- sensation (pain, reflexive inhibition)
- abnormal muscle tone (ex : hypertonia, hypotonia)
45
Explain sensory organization (systems model of balance)
- visual
- vestibular
- somatosensory/proprioceptive
However it mainly relies on proprioceptive information followed by vestibular and visual information for stability while standing on a firm surface
46
What are the 3 main roles of the vestibular system ?
- engages a number of reflexes pathways that are responsible for making a compensatory movement
- adjustments of the body position
- engages pathways that project to the cortex to provide perception of gravity and movement
47
Which structure of the inner hear respond to angular acceleration ?
How does it work ?
The ampullae
Semi circular ducts work in pairs to detect head movements : when the head turns, it excites the receptor of on ampullae and inhibits the receptors of the ampullae on the other side
48
What are the receptors of inner hear
Macula : patches of hair topped by small calcium carbonate crystals called otoconia
49
What is the role of utricule in inner hear ?
Utricule senses horizontal, linear acceleration (like in walking)
50
What is the role of saccule in inner hear ?
Saccule senses the vertical acceleration (like in falling)
51
What is the vestibulo ocular reflex ?
It controls eyes movement to stabilize the image when they move.
When the head moves in one direction, they eyes initially turn in the other direction !
52
What is the role of vestibulocollic reflex ?
It stabilizes the head in space during active body movements (locomotion). It is canceled during voluntary head movement.
53
What are the 2 main components of vestibulocollic reflex tract ?
- medial vestibulospinal tract
| - lateral vestibulospinal tract
54
To which structure are the signals from semi circular ducts sent to ?
Neck motoneurons (with the intervention of one interneuron on the vestibulocollic neuron)
55
Describe the inputs pathway along the vestibulocollic neuron
- neck motoneurons receive bilateral excitatory input from the left and the right anterior canal of the vestibulocollic neuron
- neck motoneurons receive bilateral inhibitory input from the left and the right posterior canal of the vestibulocollic neuron
56
What is the purpose of cervico collic reflex ?
Keeps the head to body relation constant
57
What is the main difference between the vestibulo collic reflex and the cervico collic reflex ?
- The vestibulo collic reflex, stabilizes the head position in relation to the gravity vector
- The cervico collic reflex, stabilizes the head position in relation to the trunk
58
What shows the Romberg test ?
An increase in body sway can be observed with eyes closed compared to eyes open.
59
Name the 5 distinct eye movement systems responsible for voluntary and reflex selection of a visual target
- vestibular
- optokinetic
- smooth pursuit
- saccadic
- vergence
60
What are the components of the somatosensory system
- muscle spindles
- golgi tendon organs
- joint receptors
- cutaneous receptors
61
What are the 5 steps of the reflex arc and their roles ?
- receptor : detects the stimulus
- sensory neuron : convey the sensory info to the brain or the spinal cord
- interneuron : relay neuron
- motor neuron : conducts the motor information to the periphery
- effector : muscle or gland
62
Classify the sensory receptors by the type of stimulus they detect
- mechanoreceptors
- nociceptors
- thermoreceptors
- photoreceptors
- chemoreceptors
63
Classify the sensory receptors according to their body location
- exteroreceptors
- interoreceptors
- proprioreceptors
64
Classify the sensory receptors according to their complexity
- complex receptors
| - simple receptors
65
Explain the environment organization of the systems model of balance
- nature of the surface ? What is its texture ? Is it moving or stationary ?
- nature of the surrounds = regulatory features of the environnement
66
Define sensory reweightening
Important mechanism for changing the relative contributions made by the different sensory systems for postural control
67
Describe the sensory reweightening on a firm surface
```
Proprioceptive = 70%
Vestibular = 20%
Visual = 10%
```
68
Describe the sensory reweightening on an unstable surface
- increase in vision and vestibular weighting
| - decrease dependance on proprioceptive inputs
