Jumping is a complex task that requires coordination of the arms and legs. Swinging the arms greatly enhances performance in the standing long jump. 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 were able to jump 21% farther when arm movement was allowed (2.09±0.03 m) compared to jumps in which arm movement was restricted (1.72±0.03 m). In this study, it was proposed that the added control provided by the arms contributed to performance improvement because the subjects were able to remedy excessive forward rotation about the mass center by swinging the arms backwards during the flight phase. In jumps with restricted arm movement, the subjects had to “hold back” during the propulsive phase of the jump to eliminate excessive forward rotation while still in contact with the ground. This tendency was manifested in restricted arm jumps in the earlier decline of the vertical ground reaction force and the development of a counterproductive backward-rotating moment about the mass center just before take-off.

To further clarify the role of arm motion in enhancing performance in the standing long jump, a joint moment and work analysis was performed on the experimental jump results. The subjects’ tendency to “hold back” in jumps with restricted arm movement was further illustrated by increases in the extension moments at the ankle and hip and in the flexion moment at the knee just before take-off that caused the subjects to achieve a more upright posture at take-off. Although swinging the arms allowed the lower body muscles to generate greater extension moments during the propulsive phase of the jump, the work analysis showed that the lower body muscles did not perform significantly more work in jumps with free arm movement. Most of the additional energy imparted to the system in free arm jumps came from work done by the upper body muscles crossing the shoulder and elbow.

Finally, 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 with a simulated annealing algorithm for jumps with free and restricted arm movement. The results validated the “hold back” theory as the activation levels of the ankle, knee, and hip joint actuators were reduced in the restricted arm jump when a constraint on the landing configuration was imposed. Furthermore, 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.