The purpose of this study was to develop a computer simulation of a forward, full twisting dive in the layout position. The results of this simulation would indicate whether the twisting rotation observed in a dive could be completely produced by the counter rotation of the diver's arms or whether part of his twisting rotating would have to be produced at takeoff.

The computer program, which simulated the airborne phase of a twisting dive was developed using a 4x4 matrix transformation technique. In the diving simulation the diver's body was modelled as a system of five inter-connected spatial linkages. The equations of motion of the 12 degrees of freedom accorded the diver's body were derived using Lagrangian mechanics.

The computer program was validated by comparing its results with those results generated by computer programs based upon force-mass-acceleration analyses. The 4x4 matrix program is not limited to only simulating twisting dives. Tt can be employed to model any mechanical system where there is at most one point of contact between the system and its environment.

The computer program predicted the translational and angular orientation of the diver's trunk-head-legs segment during the flight phase of his dive. The input data required by the program included the diver's body segment and intial takeoff parameters, and the motion of his arms, as measured relative to his trunk-head-legs segment. The diver's initial takeoff parameters were the somersaulting angle and angular velocity and the translational velocity of his L runk-head-legs segment at takeoff. Two sets of values for each of the diver's initial takeoff parameters were obtained from a search of the available literature on diving.

The arm motions employed in the diving simulations were modelled as sine functions. The angular displacements of the six degrees of freedom assigned to a diver's arms were obtained by filming two competitive divers' mimicking their twisting arm motions on dry land. The temporal data designating when the divers initiated and ceased their six arm motions were obtained from films of the divers performing their twisting dives from a one meter spring board.

There were eight separate dives simulated in this research project. Only one set of body segment parameters and arm motions were utilized in simulating all eight twisting dives.

The differences in the somersaulting, rolling, and twisting angular displacements of the simulated divers' trunk-head-legs segments at water contact were explained in terms of the divers' angular momenta. Once a diver was airborne, his absolute angular momentum had to be conserved. The relative motion of the diver's arms caused his trunk-head-legs segment to experience a rolling rotation. The diver's angle of roll reoriented his body so that his absolute angular momentum, which was determined at the instant of takeoff, produced both somersaulting and twisting rotations.

Although none of the divers simulated in this research project attained the correct somersaulting, rolling, and twisting angular displacements at water contact, the computer results did indicate that given the correct takeoff parameters and arm motions, a diver could perform a forward, full twisting dive in the layout position through the counterrotation produced by his arms. The diver's final somersaulting angular displacement was a function of his somersaulting angle and angular velocity at takeoff and his time of flight, which depended upon his translational velocity at takeoff. The change in the magnitude of the diver's roll angle was due to the angular velocities of his arms and the amount of twist he exhibited. The diver's final twisting angular displacement was a function of his somersaulting angular velocity at takeoff (i.e., his absolute angular momentum) and his angle of roll. For a diver to attain both a 0.0 rad angle of roll and a 6.3 (2 π) rad angle of twist at splashdown, he had to hold his wrap position until he had a twist angle greater than 4.7 (3 π/2) rad.