Analysis of Activities in Which 
                                the Body Rotates Free of Support


Previous Discussions have been on CG in Parabolic Motion

        High jump - parabolic motion to acheive height
        Long jump - parabolic motion to acheive length

        However, most concern with air rotation is to acheive ideal performances

               Gymnastics, Diving, Dance, etc.

Rotating Free of Support

        Rotation takes place simultainously aroud all three axis

               Anteroposterior
               Mediolateral
               Inferosuperior

               These three axis intersect at the body's CG

        When not supported, the CG _MUST_ follow a parabolic path

               Body parts can and are moved, but CG moves constantly

               Examples: Tuck, Pike, Layout, Arched

        Angular Momentum and the Human Body

               Consists of 3 Factors:
                       Mass of the performer
                       Radius of Gyration
                              CG to axis of rotation
                       Angular Velocity about axis

               As segments move,
                       Mass Distribution and Radius of Gyration change
                       Thus, the angular velocity will change

               Different positions to change ML rotation
                       Tuck - increases rate of rotation
                       Pike - slightly less increase
                       Layout - decreases rate of rotation
                       Arched - slows then increases rate of rotation
               Any segments that move, move because of internal forces
                       These result in internal momenta
                       Thess momenta will not affect the overall momentum
                              Without external forces, momentum must be conserved
                              Segmental motion cannot add or subtract to overall momentum


Segments Act a Seperate Systems

        Consider a person flying linearly throught the air (head up)

               Linear momentum is maintained 
                       parabolic path - gravity
                       constant horizontal motion

               Angular momentum is maintained
                       Body is not rotating

        Suppose person left with some angular velocity

               Causing them to rotate in an unwanted direction (say - sideways)

               What then would this person do?  Begin to rotate the arms.

        This rotation would then cause the body to move.  HOW???

        Present the second overhead.

               Because of Conservation of Angular Momentum

               As the arms rotate, they cause some angular momentum

               This must be compensated for by the remaining body to conserve momentum

               Thus, the body will begin to rotate.

               Since the mass and the radius of gyration are greater for the trunk,
                       THE BODY WILL ROTATE SLOWER.