Stability Stability and and

EqulibriumEqulibriumByBy

Dr Ajay KumarDr Ajay KumarReader Reader

School of Physical EducationSchool of Physical EducationDAVV IndoreDAVV Indore

Concept and ClassificationConcept and Classification Objects in equlibrium are classified Objects in equlibrium are classified

according to the stability of that according to the stability of that equlibrium.equlibrium.

If the position of an object is slightly If the position of an object is slightly altered and the objects tends to altered and the objects tends to resurns its original position, the resurns its original position, the objects is in stable equlibrium.objects is in stable equlibrium.

Stable

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

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

Condition for Static StabilityCondition for Static Stability

The relation of line of gravity to the The relation of line of gravity to the base of support.base of support.

:- An objects retain its equilibrium only so long :- An objects retain its equilibrium only so long as its line of gravity falls within it base of as its line of gravity falls within it base of support.support.

The height of center of gravityThe height of center of gravity:- Stability is inversely proportional to the :- Stability is inversely proportional to the

height of center of gravity.height of center of gravity.

Condition for Static Stability (cont)Condition for Static Stability (cont)

The size and shape pf base of The size and shape pf base of supportsupport

:-Stability is directly proportional to base area:-Stability is directly proportional to base area

The mass of the bodyThe mass of the body:-Stability is directly proportional to mass / :-Stability is directly proportional to mass /

weight of bodyweight of body

FrictionFriction:-Insufficient friction reduces the stability and :-Insufficient friction reduces the stability and

vice - versavice - versa

Condition for Static Stability (cont)Condition for Static Stability (cont)

SegmentationSegmentation:-Maximum stability of a segmented body is :-Maximum stability of a segmented body is

assured when the center of gravity of all assured when the center of gravity of all weight bearing segments lies in a vertical weight bearing segments lies in a vertical line which is centered over the base of line which is centered over the base of support.support.

Visual and Psychological FactorsVisual and Psychological Factors:-When walking on a danger area the visual :-When walking on a danger area the visual

stimulus may affect the stability.stimulus may affect the stability.

Condition for Static Stability (cont)Condition for Static Stability (cont)

Physiological FactorsPhysiological Factors:-The fluid found in the three semi-circular :-The fluid found in the three semi-circular

canal inside the ears is also responsible for canal inside the ears is also responsible for stability.stability.

Conditions of Dynamic StabilityConditions of Dynamic Stability

For dynamic stability to exist there For dynamic stability to exist there must be sufficient friction between must be sufficient friction between shoo surface and playing surface.shoo surface and playing surface.

In movement involving quick In movement involving quick directional change on the ground an directional change on the ground an inward lean towards the changed inward lean towards the changed direction is to be required to direction is to be required to maintain dynamic stability.maintain dynamic stability.

When the body is free in air to move When the body is free in air to move the balance or the stability can be the balance or the stability can be maintained by the application of end maintained by the application of end and middle.and middle.

When either feet and hand are When either feet and hand are supported during a movement the supported during a movement the stability can be maintained by stability can be maintained by shifting the hips or other shifting the hips or other unsupported body parts.unsupported body parts.

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

Principles of StabilityPrinciples of Stability

Principle IPrinciple I :- Other things being equal :- Other things being equal the lower the center of gravity the the lower the center of gravity the greater will be the stability.greater will be the stability.

Principle IIPrinciple II :- Greater stability is :- Greater stability is obtained if the base of support is obtained if the base of support is widened in the direction of the line of widened in the direction of the line of force.force.

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

Principle IVPrinciple IV :- Other things being :- Other things being equal, the greater the mass of the equal, the greater the mass of the body greater will be the stability.body greater will be the stability.

Principle VPrinciple V :- Other things being :- Other things being equal the most suitable position of a equal the most suitable position of a vertical segmented body is one in vertical segmented body is one in which the center of gravity of each which the center of gravity of each weight bearing segments lies in a weight bearing segments lies in a vertical line centered over the base vertical line centered over the base of supportof support

Principle VIPrinciple VI :- The other things being :- The other things being equal, the greater the friction between the equal, the greater the friction between the supporting surface and part of the body or supporting surface and part of the body or shoo in contact the more stable body will shoo in contact the more stable body will be.be.

Principle VIIPrinciple VII :- Other things being equal, a :- Other things being equal, a person has better balance in locomotion person has better balance in locomotion under difficult circumstances when he under difficult circumstances when he focuses his vision on stationary objects focuses his vision on stationary objects rather than on disturbing stimulus.rather than on disturbing stimulus.

Principle VIIIPrinciple VIII :- There is a positive :- There is a positive relationship between one’s physical relationship between one’s physical and emotional state and the ability to and emotional state and the ability to maintain stability under difficult maintain stability under difficult circumstances.circumstances.

Principle IXPrinciple IX :- Regaining equilibrium :- Regaining equilibrium is based on same principles as is based on same principles as maintaining.maintaining.