Posture & Balance

Question 1

What is considered to be the “ideal” posture ?

Answer 1

* adopted by the individual that aligns the body so torques and stress generated by gravity are minimized at each body segment

• require the least amount of energy expenditure to counteract the force of gravity on the body

Question 2

Stepping strategy

Answer 2

• Used when perturbation is large enough to move the COG outside of the BOS
• A step is taken to change the BOS and ensure that the COG will fall within it once again

If you went to far, you probably took a step forward or backwards. This is an example of stepping strategy when your COG fell outside of your base of support

Real life examples: standing on the bus, walking and being bumped into by someone else, standing on your tip toes to pick something from a high shelf

Question 3

Define COG, COM, LOG

Answer 3

Center of gravity (COG): the center of a body where all the weight is considered to be concentrated (geometrical concept)

• Center of mass (COM): “the point about which the mass of the object is evenly distributed”

COG COG

• Line of gravity (LOG): projection of the COG to the ground

Question 4

What characterize the sway back posture?

Answer 4

Swayback

• Characterized by the “slouch” posture or “relaxed”

• Pelvis forward, hip extended…compensatied for by an increased lumbar lordosis and thoracic kyphosis. The head will usually be held forwards of ideal.

knees hyperextended,

• Uses the least amount of energy (least amount of muscle work) as the maintenance of posture relies on soft tissue and ligaments

Question 5

Describe the correct sitting posture (5 points)

Answer 5

* support for the thoracic spine

* neutral lumbar spine (slight backward inclined of the chair

* 2/3 of the thighs supported by the chair

* Knees and ankles at a 90 degree angle

* Feet hip width apart on the floor

Question 6

Define Posture

Answer 6

* position of the body” (anatomic view)

“the intrinsic mechanisms of the human body that counteract gravity” (motor control view)

“the maintenance for a period of time of a position in space as a prelude for movement” (functional view)

Question 7

What is a scoliosis posture?

Are muscles shortened or lengthened on the concave side?

Answer 7

Scoliosis

• lateral curve of the spine where one side is defined as the concave and the other as the convex
• Muscles on the concave side will adapt and become shorter
• Muscles on the convex side will be elongated and weak

Question 8

Kyphosis or Kyphotic posture

What is the long-term impact of kyphosis ? consequence of Severe kyphosis ?

Answer 8

• A kyphotic posture is characterized by an increase in the anterior curvature of the thoracic spine.
• lead to increased lordosis on the cervical spine, changing the position of the head and eyes alignment
• Shortening of the chest muscles

• can impact lung function due to decrease thoracic expansion.

• likely to occur as a compensation due to shortened hip flexors

Question 9

Define Base of Support

What does it depend on?

Answer 9

• Defined as the surface area of the body that is responsible for support
• depends on the posture of the body

Question 10

What characterize hyperlordosis or hyperlordotic posture

What is kypho-lordotic posture?

Answer 10

Anterior pelvic tilt (pelvis forward), increased lumbar lordosis that shortens the spinal extensors and the hip flexors, rectus femoris and TFL, and thoracic kyphosis.

The drawing forwards of the pelvis will lengthen and weaken the glutei and abdominal muscles. • The posture is called kypholordotic when combined with a compensatory increased thoracic kyphosis.

Question 11

Explain the role of anticipatory balance control

Answer 11

It’s a mechanism where signals for postural compensation are executed before the movement itself

This allows the body to “prepare” to the disruption that a certain movement may cause

Eg 1, When bending over to pick up a heavy object from the floor: the muscles of the trunk and leg will anticipate the instability that the heavy load may cause and start to fire before you actually even pick up the weight. This will promote stability of the spine

Eg. 2: Throwing a ball with one hand: weight shift to the opposite side of the body to increase instability and efficiency for the throw.

Question 12

• How does the somatosensory system provide information to the brain?

Answer 12

• Provides information about body position
  
  • Conveying through joint receptors (Ruffini fibers)
  • Muscle spindles
  • Mechanoreceptor on foot and hand
• It is essentially subconscious and function at spinal level
  
  • Sensory information is transmitted to the spine, where motor neurons are activated to correct posture without necessary reaching higher level of the brain

Question 13

What is lordosis? Hyperlordosis?

Answer 13

Lordosis is an inward curvature found in the cervical and lumbar region of the spine.

Hyperlordosis is an increase in the curvature of the lumbar or cervical spine

Question 14

How does the body integrate all this information to create a picture of our body in space, as well as any disturbance to posture?

Sensory weighting hypothesis

Provide a real life example that supports this hypothesis

Either eliminate a proprioceptive function, visual or vestibular function

Answer 14

The central nervous system modifies the weight of each input based on its perceived accuracy

Advantage: posture can be maintained in a variety of environments even when one system is not working properly

an example of maintenance of balance without the input from one of the sensory systems (vision) • However, your body was probably able to adapt and maintain balance • This supports the Sensory weighting hypothes

Stand on one foot for 15 seconds

Question 15

How does the body integrate all this information to create a picture of our body in space, as well as any disturbance to posture?

What does the intermodal theory of sensory organization propose?

Answer 15

Intermodal theory of sensory organization hypothesis

All 3 sensory inputs contribute equally and at all times to maintenance of posture •

Question 16

Why is prone posture not recommended for prolonged period of time?

Answer 16

Full rotation of cervical spine and hyperextension of the lumbar spine

Question 17

The area of the brain responsible for interpretation and integration of all modalities of sensory information needed to plan movement is:

Select one:

a. Premotor cortex
b. Somatosensory cortex
c. Cortical associative areas

d. Visual cortex

Answer 17

c. Cortical associative areas

Question 18

A compensatory balance control strategy is performed by the dorsiflexor muscles and plantarflexor muscles.

Explain how if someone bumped into you (either from in front or behind) to cause a small pertuberation to the COG, how would the muscles acting at the ankle help to restore balance.

Answer 18

The ankle dorsiflexors and plantarflexors help to correct small pertuberation to the COG

A backwards sway, which means the COG moves posteriorly, will cause the tibialis anterior to contract to bring the COG anteriorly

Simiarly, a forward sway, would cause the gastrocnemius to bring the COG posteriorly

Question 19

Fat back posture vs Sway back posture

consequences?

Answer 19

Flat back vs Sway back

Posterior pelvis tilt (gives its characterisitc flat back) vs pelvis is pushed forward, (relies on soft tissue and ligaments)

Reduced vs . Increased lumbar lordosis

In Flat back posture –>

Tendency for shortened/tight abdominal muscles and lengthened back extensor

Prolonged flat back posture may lead to hyperextension at hips and knees and lengthened hip flexors

In Sway back posture –> characterized by the “slouch”, thoracic kyphosis, knee hyperextension

Question 20

Posture is control via the integration of vestibular, visual, and somatosensory systems

Where is the vestibular system located?

What is the function of the vestibular system have on postural control?

Answer 20

• Formed in the inner ear, by two systems: auditory and vestibular
• Functions:
• • Head orientation in relation to gravity (in space)
• • Head linear and angular acceleration (flexion, extension, bending, rotating and the rate it)
• • Is responsible for transmitting via the vestibulocochlear nerve (VIII par) (8th cranial nerve)

Question 21

When do babies develop the inward curve of the cervical spine?

Answer 21

Convex development of the cervical spine occurs by the act of lifting up the head against gravity in prone

Question 22

Hyperlordosis posture could cause what kind of influence on the pelvis? What might be the consequences of having a hyperlordosis posture?

Answer 22

1. Anterior pelvic tilt
2. Shortened spinal extensor muscle and hip flexor muscle
3. Weakened abdominal and hip extensors muscles

Question 23

Postural control can be defined as, “the act of maintaining, achieving, or restoring a state of balance during any posture or activity”(Nichols, 1996).

What two mechanism of balance control that helps to control posture

Answer 23

In biomechanics, balance is an ability to maintain the line of gravity (vertical line from centre of mass) of a body within the base of support with minimal posturalsway. Sway is the horizontal movement of the centre of gravity even when a person is standing still.

1. the ability to generate anticipatory control
2. the ability to generate compensatory reactions

For the purpose of maintaining posture.

Question 24

How does the visual system provide information to the brain?

Information is transmitted via which nerve? Where is the information carried out in the CNS ?

Answer 24

• Provides the brain with information regarding body orientation, relationship between body parts, and motion of body in relation to the environment
• Information is transmitted to the brain via optic nerve (cranial nerve II) to diff. area of the brain to help maintain and control posture.
  
  • Brainstem – eye movement control
  • Tectospinal tract – neck and head movements (activated to control posture
  • Tectopontine tract/ with added imput from the cerebellum – eye and head control •
• Outcome: eyes and head control together to ensure orientation of the head in space

Question 25

How does the vestibular system provide information to the brain?

Answer 25

• The sensory receptors in the vestibular system are constantly firing, provide constant information of head position to the brain.
• any changes in head position will change t_he rate of firing that will be processed in the brainstem_

• The information is then transmitted to other brain areas, that control muscles in the neck and trunk to make the necessary adjustment to maintain posture

For example, turning head to one side (even wtih eyes closed) the VS will provide this info to the brain. This will lead to muscle activation in the head and trunk to compensate for the change in head position

Question 26

Another mechanism of balance control is compensatory mechanisms.

Explain how this helps with balance.

Give an example why small pertuberation would not need central activation

Answer 26

• Occurs when large enough “pertuberation” disrupt the system in which compensatory mechanisms activates to maintain state of equilibrium
• Posture is constantly being challenged by external forces (perturbations) that are unpredictable. (Eg, someone bumping into you, or you stepping into a hole in the ground).
• For that, the body needs to have mechanisms of compensatory balance control to counteract external forces and maintain a stable state. (This mechanism plays a role after the movement has occurred)

The external forces need to disrupt the body’s balance enough or no “central” control

• If a small perturbations
  
  • No central control needed
  • Becauuse elastic property of muscles and spinal reflex loop can restore balance
• For example, since in standing the COG falls slightly in front of the ankle joint, calf muscles play an important role in balance control during small perturbations
• Larger perturbations
• Ankle strategy
• Hip strategy
• Stepping strategy

Question 27

What is the posture alignment in new borns?

Answer 27

1- The newborn’s spine has a concave forward-facing curve

Question 28

Important function of the vestibular system

Answer 28

This sensory system detets motion of the head, position of the head, where is the head in space. It helps to maintin balance, stabilize our head and body during movement, and maintain posture.