Measurement of force applied to javelin in javelin throwing

Kinetic analysis of javelin throwing has been a difficult subject, because the force applied to javelins is unknown and javelins are originally elastic. Therefore, a javelin with a 6-component force transducer is developed in the present reserch. The javelin is equipped with a thin pipe at the gripping position, and the pipe has elastic hinges to mesure the force by utilizing strain gages. The six components of the force applied to the javelin by one male javelin thrower is measured using the force transducer. The major results obtained are as follows; The javelin with the transducer is heavier in weight, and smaller in moment of inertia and in lower compliance at the grip as compared to the ordinary javelins. The measuring system developed is found to be satisfactory to measure the forces in javelin throw, since the relation between the measured voltages and applied forces is linear, and the resonant frequency of the transducer is higher than that of the force measured during actual javelin throw. As a result of a measuering experiment, the force components change mainly from the moment when the thrower stepped his right foot on the ground to release the javelin after run and crossover-step. The peeks of the force components apeared just before the release, and the maximum values are 14.00 kgf in the axial direction of the javelin, 7.21 kgf, 4.62 kgf in the lateral directions, 0.12 kgf・m around the axial direction, and 0.64 kgf・m, 0.77 kgf・m around the lateral directions.