Coordination of upper and lower limbs in the standing long jump: Kinematics, dynamics, and optimal control

Jumping is a complex task that requires coordination of the arms and legs. The objective of this dissertation was to quantify the performance improvement in the standing long jump when free arm movement is allowed and to gain understanding of the motor coordination principles that enable this improvement.; An experimental study revealed that subjects jumped 21% farther in jumps with free arm movement (2.09 +/- 0.03 m) than in jumps with restricted arm movement (1.72 +/- 0.03 m). Without the ability to swing the arms during flight, the subjects had to "hold back" during the propulsive phase to eliminate excessive forward rotation that would prevent proper landing. This tendency was manifested just before take-off in restricted arm jumps in the earlier decline in the vertical ground reaction force, the development of a counterproductive backwards-rotating moment about the mass center, increases in the extension moments at the ankle and hip, and greater flexion moments at the knee. Swinging the arms also allowed the lower body muscles to generate greater extension moments during key times in the propulsive phase of the jump, but overall, the lower body muscles did not perform significantly more work in free arm jumps. Most of the additional energy imparted to the system in free arm jumps came from work done by the muscles crossing the shoulder and elbow.; Optimal control simulations of the standing long jump were developed to gain additional insight into the mechanisms of enhanced performance due to arm swing. The optimal activations to maximize jump distance of a torque actuated model were determined for jumps with free and restricted arm movement with a simulated annealing algorithm. The results supported the "hold back" theory as the activations of the lower body joint actuators were reduced in the restricted arm jump when a constraint on the landing configuration was imposed. Swinging the arms allowed the lower body joint torque actuators to perform 26 J more work in the free arm jump. However, as in the experimental study, the most significant contribution to developing greater take-off velocity came from the additional 80 J work performed at the shoulder in the jump with free arm movement.