Terminology
Refers to all points of body contact w/ support surface; visualized as area enclosed within perimeter of points of contact
Base of support
maintaining upright posture during self-initiated body or body segment activation
dynamic balance
Sophisticated postural responses that occur in response to substantial displacement of the COM
Equilibrium/balance reactions
the ability to reverse movement between opposing muscle groups
Reciprocal motion
single point at which all mass of body can be considered to lie
Center of Mass
The ability to control spontaneous sway in order to sit upright (Static)
steady state
Prevent a fall after the COM moves irreparably beyond the LOS and prevent injury by one or more extremities reaching out to prop on the surface or reset/expand the BOS in the direction of the disturbance to avert a fall.
Protective reactions
movement control achieved by synergistic muscle groups acting together
single location on the support surface where the gravitational line through the center of mass would strike the floor
Center of gravity
Automatic movement patterns, or strategies, that occur when balance is disturbed
Reactive
Perturbation is slow, small
Surface is firm and larger than BOS
Muscles recruited distal to proximal
Ankle balance strategy
the ability to gauge or judge distance and speed of voluntary movement
Movement accuracy
max distance a person can intentionally move in each direction without losing balance
Limits of stability
Related adjustments happen in preparation for the expected evolution of forces during the motion
Anticipatory balance
Perturbation is fast, large
Surface is unstable or shorter than foot
Muscles recruited proximal to distal
Hip balance strategy
addresses the ability to hold the position of an individual limb or limb segment
Fixation or limb holding
maintaining upright posture in the absence of self-initiated or imposed movement
static balance
Orient the head in space and the body in relation to the head and support surface
Righting reactions
Perturbation is fast or large, OR other strategies fail
Used to prevent a fall
Step balance strategy
The sequence of coordination tests in order from least to most difficult:
1. unilateral tasks
2. bilateral symmetrical tasks
3. bilateral asymmetrical tasks
4. multi limb tasks