

The dynamic process by which the body’s
position is maintained in equilibrium.
Equilibrium means that the body is either at rest
(static equilibrium) or in steady-state motion
(dynamic equilibrium).

The body’s center of mass (COM) or center of
gravity (COG) is maintained over its base of
support (BOS).
COG, LOG, BOS
Balance control
(varying conditions)
COP& GRF
Contents
Types of Balance
Effect of Gravity on
body segments
(LOG)
Balance control
Effect of Gravity on body segments
*Center of Gravity (COG) or
Center of mass (COM)
 It is an imaginary balancing
point where the body weight
can be assumed to be
concentrated and equally
distributed.
 Anterior 2nd sacral vertebra
(adult)
Line of Gravity (LOG)
• The vertical line passing through the COG
called Line of Gravity (LOG).
Base of Support (BOS)
The boundaries of the contact area between
the body & its support surface.
Relationship between LOG & BOS
 The less height of LOG, the more stability.
 The nearest the LOG to the center of base of support,
the more stabilty.
Height
COG
LOG
Stability
Center
BOS
Newton’s law & Center Of Pressure
The location of the vertical projection of
the ground reaction force (GRF)
Effect of Gravity on body joints
LOG
Trunk
Hip
Knee
Ankle
Ant., Pos., or through Joint
Musculo
skeletal
Nervous
Contextual
effects
Balance control
 Contextual
effects that interact with the two
systems are the environment whether it is
closed (predictable with no distractions) or
open (unpredictable and with distractions),
the support surface (i.e., firm versus
slippery, stable versus unstable,
Types of balance control
Static
dynamic
Automatic

Static balance control
◦ Maintaining sitting.
◦ Half-kneeling,
◦ Tall kneeling,
◦ Standing postures on a firm surface,
◦ Tandem, Single-leg stance.
◦ Working on soft surfaces (e.g., foam, sand, grass),
◦ Narrowing the BOS, moving the arms, or closing the eyes.

1.
1.
Dynamic Balance Exercises Using Movable
Surfaces:
Swiss Ball
Tilt Boards