The Center of Gravity and Stability Flashcards
Center of Gravity
The point where all the weight of the body/object is concentrated
The center of gravity is the point where all the forces acting on the body equal _.
0
True or false: The center of gravity remains in the same location regardless of changes in body position
False. If the shape or position changes, the location of the center of gravity also changes, possibly even outside of the body.
In a standing female, the COG is about __% of standing height.
55
In a standing male, the COG is about __% of standing height
57
In quiet standing, the COG can be considered almost directly over the _______ __ _______
Center of pressure
Define the center of pressure
Point at which the force vector for ground reaction force is applied
Postural sway
As the COG shifts slightly, the COP will shift slightly in the foot-ground interface
There is _______________ sway in the sagittal plane of about 2-3cm.
Anteroposterior (AP)
There is ______________ sway in the frontal plane of about 1-2cm.
Mediolateral (ML)
An object at rest is in __________ with all forces acting upon it being __________.
equilibrium; balanced
True or False: An object at rest is stable.
False. An object at rest may or may not be stable.
An object placed so that an effort to disturb it would require its COG to be raised is in _______ equilibrium.
Stable
An object placed so that only a slight push will drop the object’s COG to a lower point is in _______ equilibrium.
Unstable
An object whose COG is neither raised nor lowered when disturbed is in ______ equilibrium.
Neutral
True or False: Human beings spend most of their time adjusting body positions for the type of equilibrium best suited to the task.
True
8 Factors that affect stability
Size/shape of base of support
Height of the COG
Relation of the line of gravity to the base of support
Mass of the body
Friction
Segmental alignment
Visual/Psychological factors
Physiological factors
The ___________ is the part of the body in contact with the supporting surface and intervening area.
base of support
As the base of support increases in size, the stability increases/decreases.
increases
To resist lateral external forces, the base of support should be widened toward/away from the direction of the oncoming force.
toward
A high/low COG increases stability.
Low
Why does a low COG increase body stability?
Because it allows greater angular displacement of the COG within the bounds of the base of support
The nearer/further the line of gravity to the center of the base of support, the greater the stability.
Nearer
Where must the COG go when a human begins to rotate about an axis?
Outside of the base of support
When a lateral external force acts on the body, stability increases/decreases if the line of gravity remains over the base even when forced to move by the force.
increases
Other things being equal, the greater the mass of a body, the greater/lesser will be its stability.
greater
Other things being equal. the most stable position of a vertical segmented body is one in which the COG of each weight-bearing segment lies in a horizontal/vertical line centered over the base of support.
vertical
Other things being equal, the greater the friction between the supporting surface and the body parts in contact with it, the more/less stable the body will be.
more
Other things being equal, a person has better balance in locomotion under difficult circumstances when the vision is focused on stationary objects/disturbing stimuli.
stationary objects
True or false: it is easier to maintain balance under difficult circumstances when one’s physical and emotional state are intact.
True
True or False: regaining equilibrium is based on the same principles as maintaining it
True
