Lec 2

• What is the center of gravity (COG)?

  The point at which all of the body’s mass is equally balanced
• What does the center of gravity represent in terms of forces and moments?

  The summation of all forces and moments at this point equals zero
• How does the shape or position of an object affect its COG?

  If an object's shape or position changes, the location of COG changes
• What is the line of gravity?

  An imaginary vertical line that passes through the center of gravity and extends towards the ground
• Why is the line of gravity important?

  It represents the direction of gravitational pull acting on the body and is crucial for maintaining balance and stability
• Where does the line of gravity pass in the upright position?

  Through the junctions of the vertebral column
• Where is the COG located in a square block with symmetrical mass distribution?

  At the center of the object
• How does asymmetrical mass distribution affect the COG?

  The COG will be nearer to the larger and heavier end
• Where is the COG located in an average adult standing upright?

  Just anterior to the second sacral vertebra
• How does age affect the location of COG?

  With advanced age, the COG becomes lower
• Where is the COG located in a newborn?

  Above the umbilicus
• Where is the COG located in a 2-year-old child?

  At the level of the umbilicus
• Where is the COG located in a 5-year-old child?

  Below the level of the umbilicus
• How does gender affect the COG?

  The COG is higher in males than in females due to muscular distribution
• What happens to the COG when a person carries a backpack?

  The COG will move backward as a compensatory mechanism
• What compensatory action occurs when a person carries weight in front of their body?

  The person will move their trunk backward to prevent falling forward
• What happens to the COG during an amputation?

  The COG moves away from the amputated limb towards the healthy side
• What should be considered when making an artificial limb?

  The weight of the artificial limb should equal the weight of the healthy limb
• What are other factors affecting the location of COG?

  Posture, structural deformities, and external forces
• What is the total COG?

  The whole weight of the body acts vertically downwards through the center of gravity
• What is segmental COG?

  The body segment acts vertically downwards through the segmental COG
• Why is determining the location of COG important in physical therapy?

  To maintain balance during interventions like gait training and weight bearing after fractures
• What is balance defined as?

  The ability to maintain the COG within its base-of-support
• What is equilibrium?

  A state of zero acceleration with no change in speed or direction
• How is stability defined?

  Resistance to a change in the body's acceleration or disturbance of equilibrium
• What is the base of support?

  The supporting area beneath the body, including points of contact with the surface
• How does the height of COG affect stability?

  The lower your center of gravity, the more stable you will be
• How does the size of the base of support affect stability?

  The larger the area of your base of support, the more stable you will be
• What is the relationship between the line of gravity and the base of support?

  The line of gravity must remain within the base of support to maintain equilibrium
• How does body mass affect stability?

  The heavier you are, the more stable you will be
• What is segmental alignment?

  When one segment gets out of line, another segment must compensate for it
• What factors can affect stability?

  Physiological, anatomical, visual factors, and physical/emotional state
• How do walking aids affect stability?

  They increase the size of the base of support, allowing more swaying without falling
• What is stable equilibrium?

  Occurs when an object is placed such that an effort to disturb it would require its COG to be raised
• What is unstable equilibrium?

  When a slight disturbance will drop the object's COG to a lower point
• What is neutral equilibrium?

  COG neither raised nor lowered when moving