Clinical Correlations - Posture Flashcards
What is the line of gravity?
the acceleration/force vector passing through the CoG to the ground
A normal line of gravity during quiet stance passes between what structures in the skull? How does a normal line of gravity pass relative to hip joint, knee joint, and ankle joint?
the mastoid processes; posterior to hip joint, anterior to knee joint, anterior to ankle joint
The projection of the line of gravity must exist within the confines of the ___ of ____
base; support
To maintain the line of gravity, at minimum, the body must rest the pull of gravity. How does it make these adjustments?
paraspinal muscles maintain proper vertebral alignment; iliofemoral ligaments and iliopsoas resist hip hyperextension; ligaments and hamstrings resist knee hyperextension; triceps surae resist dorsiflexion while the tibialis anterior resists plantarflexion; IT band stabilizes hip
When is the ankle strategy (inverted pendulum) used in regards to balance?
during quiet stance
When is the hip strategy (bending at hip/waist) used in regards to balance?
when problem is more complicated or when weak, slow
When is stepping strategy (may include flailing arms) used in regards to balance?
when challenged to limits
In regards to balance, the type of strategy used is based off of strength and reaction time to response relative to magnitude and direction of perturbation. True or false?
true
When intending to move, muscle activity in postural muscles is automatically generated prior to muscle activity of the planned volitional movement. This is a learned response that operates via a “feed-forward” mechanism. What are some examples of this?
quick arm raises quickly shift the CoG of the body anterior. Having learned this, the plan for raising the arms incorporates the activation of postural muscles prior to the onset of shoulder flexors, starting bottom up.
1st - gastrocs 2nd - hamstrings 3rd - gluteus maximus 4th - erector spinae 5th - deltoid
Unanticipated perturbations (uneven ground, obstacles, being pushed) are dealt with how?
by response patterns that are stereotyped and triggered using somatosensory, vestibular, or visual feedback.
note: “fix it after the problem occurs”
This system references the environment through touch (plantar foot on ground/hand on wall) and couples this with knowledge of skeletal arrangement.
somatosensory system
The somatosensory system can be processed within lower centers (spinal cord, brainstem). What does this allow for? What is this system very important for?
quick, reflexive control; walking
This system measures acceleration to understand the position and movement of the head as the reference, as measured by the inner ear
vestibular system
The information in the vestibular system is used reflexively coming form lower brain centers (brainstem) to directly impact postural muscles and as information to the higher brain centers for movement planning and adaptation. When is this crucial?
when performing quick, aerial movements when lacking contact with the ground
When stepping over an obstacle that is seen or altering the direction of our steps to avoid or go around an obstacle, we are using this system
visual system
Vision assesses ___ orientation
vertical (gravity)
Vision is the strongest, most trusted of the sensory inputs, however it can be easily fooled. True or false?
true
Proper use of the three sensory systems comes with combining and weighting the importance of each for purposes of solving the postural problem. When vision is absent, the ____ system dramatically increases its usefulness
somatosensory
ex: closing eyes and then using hands to feel things in order to walk straight
This system refers to the positions of various body parts relative to each other
egocentric coordinate system
This system refers to the position of body parts relative to the environment
exocentric coordinate system
This system refers to the position of body parts related to gravity
geocentric coordinate system
The egocentric, exocentric, and geocentric systems solve the problem of ___ and ____ stance
erect; bipedal
The pelvis becomes important in the transfer and distribution of weight due to gravity. In the normal standing position, the body’s weight is distributed evenly between the two lower limbs. Using simple mechanics, a weight of 150lbs at S2 is translated to a force of ___ lbs at each hip joint. What would this force be if the person was counterbalancing on one leg?
75; 300lbs
The hip joint of the stance limb in unilateral stance experiences how much force?
sum of body’s weight plus the counterbalancing force of the hip abductors (150 + 300 = 450 lbs)
True or false? Articular cartilage is loaded with nerve endings. Bone, ligaments, and synovial membranes, however, have none.
False; articular cartilage has none but bones, ligaments, and synovial membranes have pain fibers.
note: reason why under normal conditions, you do not feel the compression force in joints
To minimize the pain in an abnormal joint, the posture is shifted to minimize the compression force. This can be manifested how?
limp or shift in the curvatures in vertebral column
