Center of Mass

CoM & CoG

Center of GravityA point at or near the object through

which the resultant weight of the object passes

Center of Mass point at which the object's mass can

be assumed, for many purposes, to be concentrated

COM

• The point around which a body’s weight is equally balanced in all directions• Also referred to as the center of mass or mass centroid• Need not be physically located inside of a body

Center of Mass

• Specific point at which a system of particles behaves • a concentrated system• a function of only the positions and masses of particles comprising a system.

a) Neutralb) Stablec) Unstable

Center of Gravity

Serves as an index of total body motionBy locating CM can analyze motion of the

entire system as distinguished from the motion of its individual parts

Path of the center of gravity of a runner.

Methods to assess CG

1. Reaction Board technique which is easily applied to static positions

2. Balance Board technique which has limited application and is used for static positions

3. Segmentation method involves an estimation of individual segment masses and positions

Balance Board Technique

Reaction Board Technique

Segmental Method

Position of the end points of all of the body’s segments

Mass of each segmentLocation of CoM within each segment

Segmental Method

14 body segments:TrunkHead and neckRight and left thighsRight and left lower legsRight and left feetRight and left upper armsRight and left lower armsRight and left hands

Each segment has its own CoM