PT Activity Examination: Balance and Trunk Control Flashcards
base of support (BOS)
boundary created by body parts in contact w supporting surface
center of mass (COM)
mean/avg location of total mass in the body
center of pressure (COP)
theoretical position under BOS through which all forces act on the body
- weighted avg (net force) of all forces acting on supports
ie imaginary point where all pressure is located (right vs left, toes vs heels)
center of gravity (COG)
mean location of moments and forces acting on a body
- imaginary point about which sum of forces and moments equal ZERO
limits of stability (LOS)
COG approaches BOS; further distance a person can WTS without LOB or altering the original BOS
- influenced by a person’s height, foot length, confidence
what are two ways to define balance
ability to control COG relative to BOS
ability to achieve and maintain postural orientation and stability for function
what does adaptive postural control require
sensory and motor modifications as task and environment changes
balance is an ACTIVITY that emerges from the complex interaction of:
- sensory systems responsible for detection of body position and motion
- CNS integration processes
- motor systems responsible for execution of motor responses
how does the incidence falls related to age
inc as you get older
- 30 at >65yo
- 42-49 at >75yo
- 83 at >85yo
how is neurological dysfunction related to the incidence of falls
5x more likely
why is the inc incidence of falls w age so significant
falls account for 50% of injury related deaths in older adults d/t
- severe disability
- wounds/infections
- ability to mobilize
- people might not know they fell
what is the impact on the healthcare system from inc incidence of falls w age
costly public health crisis
- surgery, hospital stay, rehab/SNF
what are 6 anatomical and physiological functions/processes contribute to balance
sensory orientation
motor function
biomechanical constraints
stability limits
anticipatory postural adjustments
- proactive balance
postural responses
- reactive balance
what is anticipatory or proactive balance
anticipation of a destabilizing force
- ms activation prior to expected COG disturbance by an internal perturbation
what drives proactive balance
feedforward mechanisms drive response based on past experiences and established motor programs
how is proactive balance seen in infants and young children
presence of righting and equilibrium reactions
what is reactive postural response
displacement of COG requiring motor response and/or changes in BOS
what drives reactive postural responses
sensory inputs drive corrective response (feedback)
what are displacement forces that trigger reactive postural responses
external forces or perturbations
- train stops, someone bumps into you
internal forces - LOB
what are perturbations
something that is destabilizing
what are reactive balance responses (3)
ankle strategy
hip strategy
stepping strategy
describe ankle strategy
small shifts of COG within LOS
- feet maintained on ground
body rotates as a rigid mass about the ankle joints
how does ankle strategy often manifest itself
anterior/posterior sway
when is ankle strategy used
ALLLLLL THE TIME
- smaller forces
when is hip strategy used
elicited w faster, larger amplitudes of COG displacement
when is hip strategy most effective
when COG is near BOS or when support surface is small, variable
when is hip strategy required
lateral displacement in COG via hip ABD/ADD
- due to nature of movement at hip
when is stepping strategy used
when COG displaced beyond BOS and outside LOS
how does stepping strategy work
establish new BOS in which COG is maintained
- take a step or steps to prevent a fall
- in sitting may have UE ext also
when is stepping strategy elicited
by larger and/or fast amplitude and external perturbation
how is BOS changed by someone sitting down
BOS includes all body parts in contact w a support surface
describe postural responses in sitting
trunk moves on hips
-if feet on supporting surfaces, gastroc and soleus may be activated
describe postural responses in sitting to posterior excursion of COG
ie leaning back
- hip flexors fire first
- then abs
- then neck flexors
extensors fire for anterior displacement of COG
what postural responses in sitting do you see to large, quick excursions in COG
protective extension
step responses
trying to establish larger, more stable BOS
what is required for sensorimotor integration in balance
complex interactions of musculoskeletal and neural systems required
what provides sensory input for balance
joint and muscle proprioceptors
cutaneous and pressure receptors
what information are your sensory receptors providing in terms of balance
relationship of body to supporting surface
what sensory input is provided by visual proprioception (3)
- perceive movement of objects
- recognition of environmental factors
- perception of verticality or orientation of self to the environment
sensory input from the vestibular system: otoliths vs semicircular canals
OTOLITHS - position of head in relation to gravity and linear acceleration
SEMICIRCULAR CANALS - info on angular/rotary motions of the head
what are the two otolith organs? how does their function differ?
saccule - vertical info
utricle - horizontal info