What is balance? (2 definitions)
- ability to maintain body’s position in equilibrium
- ability to maintain the body’s center of gravity over the base of support
what is center of gravity?
hypothetical point at which body’s mass appears to be concentrated and from which gravity appears to act
where is COG located?
slightly anterior to S2 vertebra
what is the base of support?
the perimeter of contact area between body and its support surface
how does someone fall?
when the COG goes beyond and outside of the BOS
What are the systems which work together to maitain balance?
- sensory systems: provide sensory input on whether someone is balanced or not
- integrating system: sensory input is processed and integrated
- motor output: integrating system sends information to motor areas of the body -> decide if any motor activities are required to maintain balance
What are the 3 main areas for sensory input?
- visual system
- vestibular system
- somatosensory system
What is the role of the visual system?
tells us about:
- relative position of head and body in space
- direction and speed of movement
What is the role of the vestibular system?
receptors in inner ear tell us about
- our head position
- movement and acceleration (with respect to gravity and inertia)
what is the role of the somatosensory system?
- provide info about proprioception
- > where your joint position is in space
- > sense of limb movement
where in the brain is sensory input integrated and processed? (3)
- cerebellum
- basal ganglia
- supplementary motor area
what are the 3 main motor output responses for maintenance of balance?
- hip strategy
- ankle strategy
- stepping stategy
what happens in the hip strategy?
- pelvis moves in opposite direction of sway/fall
- for larger and more rapid displacements
what happens in ankle strategy?
- ankle either dorsiflexes/plantarflexes on the opposite direction to fall
- usually used for small and slow displacements (used rather to maintain balance than prevent fall)
what happens in stepping strategy?
- a step is taken either forwards/backwards (opposite to direction of displacement)
- usually occurs when COG displacement is too big to use ankle/hip strategy to maintain balance
- works by increasing BOS
7 causes of impaired balance
- lower limb pathology (decreased muscle strength and flexibility)
- spinal pathology (affects motor nerves which slow down motor responses)
- visual deficits
- vestibular system conditions/injuries
- brain injuries
- neurological conditions (decrease central processing of sensory info)
- ageing (older people have less balance due to change in soft tissue, mechanoreceptors and reaction time)
definition of balance training
- an exercise programme which requires patients to maintain balance during static and dynamic activities which progressively get more difficult
what are the benefits of balance training (7)
- improve balance measures
- reduce risk of injuries due to falls
- improve strength
- improve posture
- improve physical functioning (eg: increase walking speed by decreasing fear in falling)
- improve standing balance and locomotor performance in elderly
- improve quality of life
11 ways to progress balance training
- supported -> unsupported
- bilateral -> unilateral
- large BOS -> small BOS
- PWB -> FWB
- stable -> unstable surface
- visual input -> no visual input
- static -> dynamic balance
- add limb and head movements
- add distractions
- give perturbation
- move outside BOS
what are the contraindications for balance exercises?
- when can increase pain/inflammation
- when will disrupt healing process/surgical repair
- when patients are inherently unsafe in balance-challenged positions
what happens (physiologically) when someone carries out balance exercises? (3)
- decrease in cortical brain activity, but increase in subcortical brain activity (increased skill acquisition)
- decrease in excitability of spinal reflexes (decrease in unwanted reflex joint oscillations -> throw someone even more off balance)
- improved movement control and more refined balance (muscle activation controlled more by brain centers)
what are the outcome measures/tests used for balance
- berg balance scale
- functional reach test
- timed get up and go test
- 10m/any distance walk test
