Kin10

• Center of Gravity (COG)


  The total body COG can be determined using mathematical or laboratory methods

  
• Mathematical determination of COG

  1. Croskey formula (regarding to sex)

  2. Palmar formula (regardless to sex)
• Croskey formula


  Calculates COG location in both male and female
• Palmar formula


  Calculates COG regardless to the subject sex by multiplying 55.7% of height and then adding 1.4

  
• Laboratory method (reaction board method)

  1. Segmental length *4/7= location of segmental COG

  2. The result number will be the distance from the distal end

  
• Segmental body Centre of Gravity

  • In amputation, segmental COG is very important for artificial limb weight manufacture
  • If the weight of the artificial limb increased, the total COG will shift towards the heaviest body part, increasing pain
• Stability


  • The ability to maintain balance in static and dynamic situations
  • The individual ability to maintain their line of gravity within their Base of Support (BOS)
  • The resistance to over throwing or sudden change of the body's position
• Factors Affecting Stability


  • Size and Shape of the Base of Support
  • Height of the Center of Gravity
  • Relationship of the Line of Gravity to the Base of Support
  • Mass of the Body
  • Age

  
• Base of Support (BOS)

  • The supporting area under the body
  • Includes the point of contact with the supporting surface and the area between them
  • Center of gravity (COG) must remain within the base of support in order to maintain equilibrium
• If the feet are separated

  The base is widened and the equilibrium improved
• If the person is supported by crutches

  • The base of support encompasses the area bounded by the feet and crutches
  • Placing the crutches forward makes a triangular base instead of a linear one, increasing stability
• If the arms are raised or if a weight is carried above waist level

  The center of gravity shifts to a higher position, making it more difficult to maintain equilibrium

  
• Lowering the center of gravity

  Increases the stability of the body because it allows greater angular displacement of the center of gravity within the bounds of the base of support
• Line of Gravity


  • The vertical line that passes through the COG and falls within the BOS
  • To maintain equilibrium, line of gravity must remain within the base of support
  • The nearer the line of gravity to the center of the base of support, the greater the stability
  • The nearer the line of gravity to the edge of the base of support, the less the stability

  
• In standing with leaning the trunk toward the toes or when standing on toes

  The line of gravity is nearer to the edge of the base of support, decreasing stability
• To maintain stability


  The line of gravity should fall within the BOS
• Age


  • The person will be more stable in adulthood period than in childhood
  • The stability will also decrease in older subjects due to the physiological changes occurring as a result of aging process