Balance & Postural Control

What is postural control AKA?

balance

What is the definition of postural control?

the ability to control the body's position in space with respect to gravity, support surfaces, visual surround and internal reference for dual purposes of stability and orientation

What is stability definition?

the ability to control the body's COM in relation to the BOS under quasi static and dynamic conditions

What is orientation definition?

relationship between the body's segments and between the body & environment

What is COG?

center of gravity; imaginary point in space, calculated biomechanically from measured forces & moments where the sum total of all forces = zero;

Where is the body's center of mass?

S1-S3

What is BOS?

base of support; body surface that receives pressure as the result of body weight & gravity

What is LOS?

limits of stability; farthest distance a body can lean in any direction without altering the original BOS

What is the difference between perceived and actual LOS?

perceived = how forward a pt thinks they can lean without losing balance

actual = the actual cone of stability in which a pt can lean without losing balance

Why is the cone of stability greater anterior to the body?

the forward lean has an advantage because of the feet provide more support and the pt can see where they are when they are leaning forward

How will the LOS change if a pt has an involved L side?

LOS will shift to the R side

What are the sensory components of postural control?

-somatosensory system

-visual system

-vestibular system

What is the role of the somatosensory system in posture control?

provides CNS with position and motion info about the body's position in space in reference to the support surface; feet feeling surface on ground

What is the role of the visual system in posture control?

provides info regarding the position & motion of the head with respect to surrounding objects

What is the role of the vestibular system in postural control?

provides info regarding position and movement of the head with respect to gravity & inertial forces

What system is "the boss" when systems are in conflict with one another when considering the sensory components of postural control?

vestibular system

What is the structure of the vestibular system? What does each portion do?

1. semi-circular canals = directionally sensitive to angular acceleration; VOR

2. vestibule with utricle & saccule (hair cells) = detects linear acceleration and gravity; static head position

In general what are the functions of the vestibular system in regard to posture control?

1. detect position & motion of the body in space

2. control COM via VSR

3. gaze stability via VOR

4. orient head & body to vertical with respect to gravity

5. resolve inter-sensory conflict

What are movement strategies?

type of automatic postural response to keep to COG over the BOS; functionally organized long-loop responses to keep the body in a state of equilibrium

What are the types of movement strategies?

ankle, hip, stepping strategies

What is an ankle strategy?

-movement to control the COG by rotating the body around the ankle joints with in-phase movement of head & hips

-distal muscle activation

-utilized in response to small perturbations on firm surfaces

If the force plate, in which a pt is standing on, moves minimally backwards what is the sequence of muscle firing as a movement strategy?

ankle strategy kicks in and the muscle activate in a distal to proximal fashion

gastro, hamstring, paraspinals

If the force plate, in which a pt is standing on, moves minimally forwards what is the sequence of muscle firing as a movement strategy?

ankle strategy kicks in and the muscle activates in a distal to proximal fashion

tibialis anterior, quads, abdominals

Will an ankle strategy occur on a firm surface?

Yes, must be a firm surface

Will an ankle strategy occur with a large perturbation?

No, needs to be small

What is a hip strategy?

-movement strategy to control COG with large and rapid motion at the hip & anti phase movement of the head

-muscle activation occurs proximally

-utilized in response to large fast perturbations or when support surface is unstable or narrow

If the force plate, in which a pt is standing on, moves quickly and with a large amplitude backwards what is the sequence of muscle firing as a movement strategy?

hip strategy occurs proximally then distally

abdominals & quads fire

If the force plate, in which a pt is standing on, moves quickly and with a large amplitude forwards what is the sequence of muscle firing as a movement strategy?

hip strategy occurs proximally then distally

hamstring & paraspinals fire

What type of movement strategy is used in response to large fast perturbations?

hip strategy

T or F: With hip strategies, the head and hips move in opposite directions

True

What is a stepping strategy?

change the base of support when the perturbation is strong enough to displace the COG outside the BOS

The push and release tests what type of balance?

reactive balance

What is steady state postural control?

-ability to control the location of the body's COM within the area defined by the BOS under predictable, quasi-static conditions

-adopt motor behavior to meet demands of different task & environmental conditions

What are the 3 types of balance control strategies?

steady state, anticipatory, reactive

What is anticipatory postural control?

-ability to generate postural adjustments prior to the onset of and during voluntary movement for the purpose of countering an upcoming postural disturbance

What is reactive postural control?

-ability to respond to sensory input that signals a need for a response to ensure successful maintenance of postural control

-need for a response is unanticipated but may be generated externally (perturbation) or secondary to an internal generated movement (like leaning to far, or grabbing something too heavy)

What is it called when a pt responds to unanticipated movement, either generated internally or externally?

reactive postural control

What are musculoskeletal determinant of balance?

-ROM

-flexibility

-muscle performance

-alignment

What are neuromuscular determinants of balance?

-postural movement strategies

-coordination

-sensory integrity

-sensory processing (integration)

-perceptual function (verticality)

What are cognitive/mental function determinants of balance?

-executive function

-multi-task capacity

-arousal and alertness

What hemisphere of the brain influences executive function?

R hemisphere

What are the behavioral factors that influence balance?

-balance confidence

-falls self-efficacy

-fear of falling

-activity avoidance

What is self efficacy?

the belief that one can master a situation and produce favorable outcomes

T or F: Utilizing "poor, fair, and good" are reasonable descriptions for balance

false you idiot

What are examples of steady state balance tests?

-romberg

-sharpened romberg

-SLS

-one-legged stance time (OLST)

-postural sway

What are examples of perturbed balance tests?

-nudge/push test

-motor control test (MCT)

What is a way to evaluate sensory integration when examining balance?

sensory organization test (SOT)

What are examples of active standing balance exams?

-functional reach (FR)

-multidirectional reach test (MDRT)

-limits of stability (LOS)

What are examples of task performance balance exam tests?

-observation ANPT 6 core tasks

-BBS

-TUG

-Tinetti POMA

-community balance and mobility scale (CB&M)

-short physical performance battery (SPPB)

-fullerton advanced balance scale (FAB)

-postural assessment scale (PASS)

-trunk impairment scale (TIS)

What are gait examination balance tests?

-DGI

-FGA

-emory functional ambulation profile (E-FAP)

What are examples of dual task balance tests?

-stops walking when talking (SWWT)

-multiple tasks test (MTT)

-TUGman or TUGcog

What are self report measures for balance exam?

-fall efficacy scale (FES)

-activities-specific balance confidence scale (ABC)

-dizziness handicap inventory (DHI)

-fall logs/diaries

What are specialized vestibular testing exam measures?

-dix-hallpike manuever

-vertiginous positions

-oculomotor tests

-VOR tests

-dynamic visual acuity

-Fakuda stepping test

-complex gait tasks (DGI)

What are all the underlying determinants of balance?

-musculoskeletal

-neuromuscular

-cognitive/mental function

-behavioral factors

What are the 6 core tasks to evaluate balance?

sitting, standing, reaching/grasping/manipulating, sit to stand, step up.down, walk & turn

What are the main categories for diagnostic labels for movement system diagnoses?

-deficit in steady state postural control (SSPC)

-deficit in anticipatory postural control (APC)

-deficit in reactive postural control (RPC)