Stability and Equlibrium By Dr Ajay Kumar Reader School of Physical Education DAVV Indore

Concept and Classification  Objects in equlibrium are classified according to the stability of that equlibrium.  If the position of an object is slightly altered and the objects tends to resurns its original position, the objects is in stable equlibrium. Stable

 Unstable equilibrium exists when it takes only a slight push to destroy it.

 The third classification of equilibrium is called neutral equilibrium and exist when an objects center of gravity is neither raised nor lowered when it is disturbed. A ball lying on floor is in neutral equilibrium.

Condition for Static Stability  The relation of line of gravity to the base of support. :- An objects retain its equilibrium only so long as its line of gravity falls within it base of support.  The height of center of gravity :- Stability is inversely proportional to the height of center of gravity.

Condition for Static Stability (cont)  The size and shape pf base of support :-Stability is directly proportional to base area  The mass of the body :-Stability is directly proportional to mass / weight of body  Friction :-Insufficient friction reduces the stability and vice - versa

Condition for Static Stability (cont)  Segmentation :-Maximum stability of a segmented body is assured when the center of gravity of all weight bearing segments lies in a vertical line which is centered over the base of support.  Visual and Psychological Factors :-When walking on a danger area the visual stimulus may affect the stability.

Condition for Static Stability (cont)  Physiological Factors :-The fluid found in the three semi-circular canal inside the ears is also responsible for stability.

Conditions of Dynamic Stability  For dynamic stability to exist there must be sufficient friction between shoo surface and playing surface.  In movement involving quick directional change on the ground an inward lean towards the changed direction is to be required to maintain dynamic stability.

 When the body is free in air to move the balance or the stability can be maintained by the application of end and middle.  When either feet and hand are supported during a movement the stability can be maintained by shifting the hips or other unsupported body parts.

 Majority of the times dynamic stability or equilibrium is obtained involuntarily by the physiological mechanism governing posture and equilibrium, which includes kinesthetic perception and certain body reflexes.

Principles of Stability  Principle I :- Other things being equal the lower the center of gravity the greater will be the stability.  Principle II :- Greater stability is obtained if the base of support is widened in the direction of the line of force.

 Principle III :-For maximum stability the line of gravity should intersect the base of support at a point which will allow greatest range of movement within the area of the base in the direction of force causing motion.

 Principle IV :- Other things being equal, the greater the mass of the body greater will be the stability.  Principle V :- Other things being equal the most suitable position of a vertical segmented body is one in which the center of gravity of each weight bearing segments lies in a vertical line centered over the base of support

 Principle VI :- The other things being equal, the greater the friction between the supporting surface and part of the body or shoo in contact the more stable body will be.  Principle VII :- Other things being equal, a person has better balance in locomotion under difficult circumstances when he focuses his vision on stationary objects rather than on disturbing stimulus.

 Principle VIII :- There is a positive relationship between one’s physical and emotional state and the ability to maintain stability under difficult circumstances.  Principle IX :- Regaining equilibrium is based on same principles as maintaining.