Postural Control and Balance: Lecture 4 Flashcards
Postural stability
Ability to control center of mass over base of support
Postural orientation
Ability to maintain relationship between body segments and between body and environment for a task
Vestibular system
Gaze stabilization
- vestibulo-ocular reflex (VOR) is the mechanism for stabilizing gaze during head movement
Provides sensory information for spatial orientation
Maintains postural stability in stationary and dynamic situations - motor output
Stabilizing head is important to controlling locomotion
Somatosensory system
Recognizes relative body movements and position
Base of support, joint proprioception, pressure
Central processing
Adaptive strategies change with demands of task and environment
Anticipatory strategies “pre-tune” sensory and motor systems based on prior learning
Cognitive “override”
- consider motivation, intent, attention
Vestibulo-ocular reflex (VOR)
Stabilizes gaze during head movement
- VOR is intact and mature by 1 y/o
Vestibulo-spinal reflex (VSR)
Coordinates head and body movements to maintain head in upright position
Medial vestibulo-spinal tract (MVST)
- cervical connections
- vestibulo-cervical reflexes for head righting
Lateral vestibulo-spinal tract (LVST)
- adjusts limb movement for balance
Cervico-spinal reflex (CSR)
Tonic neck reflexes
- asymmetric tonic neck reflex (ATNR)
– neck rotation excites ipsilateral extensors and contralateral flexors
- symmetrical tonic neck reflex (STNR)
– neck flexed excites bilateral UE flexors and LE extensors
Postural control responses
Non-reflexic strategies
Ankle - somatosensory
Hip - vestibular
Stepping - vestibular
Steady-state balance
The body does not collapse in response to the pull of gravity
- intrinsic stiffness of muscles
- background muscle tone
- postural tone
Reactive balance
Requires feedback control
Occurs in response to sensory feedback from an external perturbation
Ankle, hip, stepping
Proactive/Anticipatory balance
Requires feedforward control
Postural adjustments are made in anticipation of voluntary movement
Aging and postural control
Decrease
- timely activation of postural responses (reactive balance)
- ankle responses (more hip-dominated)
- ability to stabilize body during movement tasks (anticipatory balance)
- adaptation to changing task and environmental demands
- vision, somatosensory, vestibular function
Increase
- hip, knee, trunk flexion
- UE use
Balance questionnaires
- Activities of balance confidence (ABC)
- Falls efficacy scale (FES)
Patient-reported
Balance tests and measures
- berg balance scale (BBS)
- Performance orientated mobility assessment (POMA, Tinetti)
- 3 meter backwards walk test
- clinical test for sensory interaction in balance (CTSIB)
- balance evaluation systems test (BEST, mini-BEST)
- four square step test
