Author(s): WAKATSUKI, T., KAWATA, K., TANAKA, H., Institution: TOKYO UNIVERSITY OF AGRICULTURE AND TECHNOLOGY, Country: JAPAN, Abstract-ID: 660

INTRODUCTION:
In target-aiming motor tasks, increasing target distance instinctively evokes the need for greater force exertion. For example, in golf, demands for greater distance often trigger “over-swinging”—an excessive force exertion that paradoxically degrades performance. We propose that this phenomenon arises from a “speed-dominant adjustment” strategy. Although actual ball distance is determined by both launch angle and velocity, humans tend to perceive speed control as a more intuitive and reliable variable than angle control. Consequently, performers increase movement speed even when the required distance could be achieved solely through angle adjustments. We hypothesized that this distance-induced over-powering compromises movement smoothness and tested this hypothesis using a target-aiming throwing task.
METHODS:
Thirteen participants performed a ball throwing task toward targets at two distances (3.0 m and 4.5 m) under two instruction conditions: accuracy-over-velocity (AV) and velocity-over-accuracy (VA). Ball release velocity, release angle, and release height were measured. Movement smoothness was quantified using jerk cost (JC), calculated from the angular kinematics of the wrist, elbow, and shoulder joints. Using a flight-trajectory simulation that incorporated air resistance, the theoretical minimum angle required to reach 4.5 m was computed based on the measured release velocity in the 3.0 m condition.
RESULTS:
A two-way ANOVA revealed that both release velocity and release angle increased significantly with target distance and instruction condition, with no interaction effects. Notably, in the VA condition, the measured release angle at 4.5 m was statistically equivalent to the theoretical angle required to reach the target using the 3.0 m release velocity. This indicates that participants had already secured a kinematic configuration sufficient to extend the reachable distance to 4.5 m without additional acceleration. Nevertheless, participants significantly increased their velocity. This superfluous increase in speed was accompanied by significant increases in JC at the elbow and shoulder joints, indicating reduced movement smoothness.
CONCLUSION:
The absence of interaction effects suggests that distance-dependent increases in movement speed are a robust feature of motor scaling. Critically, the VA-condition results provide direct evidence of over-powering: participants applied additional power despite already possessing a kinematic configuration that was physically sufficient to achieve the required throwing distance. The concomitant increase in JC suggests that prioritizing speed over strategic angle adjustment disrupts motor coordination efficiency. These findings demonstrate that “trying too hard” to overcome distance through speed leads to kinematic degradation, offering a mechanistic explanation for suboptimal performance in far-aiming motor tasks.