Kin9

• Center of Gravity (COG)


  An imaginary balancing point around which the force of gravity appears to act
• Center of Gravity (COG)


  • The point at which the combined mass of the body appears to be concentrated and equally distributed, and around which the body may rotate freely in all directions
  • In the anatomical position, the COG lies approximately anterior to the second sacral vertebra
  • The point of intersection of the three cardinal body planes (sagittal, frontal and transverse)

  
• Human beings do not remain fixed in the anatomical position, so the precise location of the COG changes constantly with every new position of the body and limbs
• The bodily proportions of the individual will also affect the location of the COG
• COG

  • The balancing, equilibrium or pivoting point
  • The point where the sum of all the forces and force movements acting on the body is zero
  • All the linear forces acting on the body at this point equal zero
  • All the rotary forces (torques) at this point equal zero
• Location of COG


  • If the object is asymmetrically distributed, the COG is near to the heavier and larger part
• Age


  • Since body segments differ in proportion to total height from birth to maturity, the transverse plane of the center of gravity will lie in a different section of the body as age increase, but the proportion of height will be constant
  • The level of the COG will gradually decrease till it reaches the level of the second sacral vertebra at adulthood
  • In newborn, location of COG is above the level of umbilicus
  • At 2 years, location of COG is at the level of umbilicus
  • At 5 years, location of COG is below the umbilicus
  • In adult, anterior to the second sacral vertebra
  • As newborn, the largest and heaviest part is in the upper part, in development redistribution of the body mass occur, so lowering of the COG
• Sex or Gender

  • The distribution of body mass differs from males to females
  • In males, the upper portion is heavier than the lower portion
  • In females, the pelvis is wider and lower than the male
  • The COG will be located higher in males than in females
• Position of any segment in relation to the total body segment on of COG


  • Change of the body segment affects the location of COG, shifting it toward the heavy
  • Flexion of the left upper limb movement of COG upward, forward and to the left
• Addition or subtractions of weight in some parts of the body


  • Carrying weight will move the COG towards the location of load
  • Carrying a weight above the head will raise it upwards
  • Carrying a weight behind the trunk will move the COG backwards
  • Carrying a weight in front of the trunk, the COG will move forward
  • If a person carries a backpack, the COG will move backward as a compensatory mechanism, the person will move his trunk forward (kyphosis) to prevent falling
  • If a person carries weight in front of his body, the COG will move forward as a compensatory mechanism, the person will move his trunk backward (lordosis) to prevent falling forward