lecture 2 Flashcards
why should we study balance?
balance serves as a platform to support and facilitate volitional movements: goal-directed, episodic, rhythmical.
what is mobility?
the ability to move independently and safely from one place to another
how does balance affect mobility?
balance affects locomotion. Poor locomotion affects independent and safe movement
what are the discussed consequences of mobility dysfunction?
- Physical and social activity restrictions.
- Loss of independence.
- Reduced quality of life.
- falls.
what is a fall?
unplanned, unexpected contact with a supporting surface
what is postural control
Ability to control the body’s position in space to maintain stability and orientation
define postural orientation
- Alignment of body parts and body orientation with respect to the environment.
- Commonly oriented relative to gravity in daily life.
what are the 3 coordinate systems for postural orientation
- egocentric
- exocentric
- geocentric
define egocentric
Relative position of body parts to one another.
define exocentric
Relative position of body parts to the environment.
define geocentric
Relative position of body parts to the gravitational field
why is postural orientation important
Good postural orientation minimizes muscle activity needed to counteract gravity
what are anti gravity muscles?
muscles that are tonically active when maintaining posture
what is postural tone
level of anti gravity muscle activity
what are some causes of poor postural orientation?
- musculoskeletal deficits (e.g. osteoporosis)
- neurological deficits (e.g., stroke, Parkinson’s).
what is postural stability
process that controls the body’s center of mass (COM) with respect to its base of support (BOS)
how is balance related to postural stability?
Balance is the process of maintaining postural stability
define center of mass
- COM is the point equivalent of total body mass in a global reference system.
- if multi segmented, the total COM
is the weighted average of the COM of each body segment
what happens to COM in uniform gravity?
COM = center of gravity (COG)
define line of gravity
the vertical projection of COM on the ground
define base of support (BOS)
the area enclosed by the outermost edges of supporting structures
that contact the environment and thereby allows ground reaction forces
to be generated
how does the relationship between BOS and COM affect postural stability?
As long as the COM stays within the BOS, postural stability is maintained
what is static equillibrium?
- when all opposing forces acting on the body are equal so that the body rests in an intended position
- COM must lie within BOS
what are the 3 types of static equillibrium?
- stable
- unstable
- neutral
what is stable static equillibrium?
After a small force is applied, the object/body will return to its original equilibrium position
what is unstable static equillibrium
After a small force is applied, the object/body will
not return to its original equilibrium
position and moves to a new equilibrium position
define neutral static equillibrium
Even with a large force applied, the object will not change equilibrium position
why is balance control difficult for humans
- 2/3s of bodyweight is located 2/3 of height above ground
- must maintain COM with large moment arm within small BOS
what are two ways to make balance easier for humans?
- wider stance (larger BOS)
- lower stance (allows more angular displacement without exceeding BOS)
