SPINAL MECHANICS AND POSTURE
WEEK 6
READING
QUESTION OR TERM
Centre of gravity?
Centre of pressure
Postural sway
Stable equilibrium
Unstable equilibrium
Neutral equilibrium
Where is postural sway measured?
What are three factors that affect stability?
How do you find balance and equilibrium?
Does the centre of gravity change?
Where is the centre of gravity in female?
Where is the centre of gravity in males
What happens with postural sway in the
elderly?
What happens if there is evidence of
excessive postural sway?
ANSWER OR DEFINITION
Point where all the weight in the body is
concentrated
Point at which force vector for ground
reaction force is applied.
As centre of gravity moves, the centre of
pressure will move.
In order to disturb the object, it’s centre of
gravity must be raised. The lower the
centre of gravity, the more stability there is
Only takes a slight push to destroy balance
COG neither raised nor lowered when
disturbed and the object can come to rest
in any position without any change to the
COG.
In the sagittal and frontal plane
-Height of COG
-base of support
-Relation of line of gravity to base of
support
 All linear and rotary forces must be
balanced.
 Eg; If there is downward linear
force, the upward linear force
causes the vector sum to be zero.
Not if the shape of the object stays the
same. If an objects shape or position
changes, so will the centre of gravity.
Transverse plane approx 55% of standing
height
Transverse plane appox 57% of standing
height
An increase in postural sway can render
elderly a falls risk.
It indicates that there are problems with
stability.