Author(s): MURAKAMI, H., YAMADA, N., Institution: KINJO UNIVERSITY, Country: JAPAN, Abstract-ID: 1551

INTRODUCTION:
Movement in humans is thought to be governed by a tradeoff between speed and accuracy (1, 2). However, studies that have examined whole-body movement (e.g. sports) have reported inconsistent findings regarding this relationship. Recently, we examined the relationship between speed and accuracy and its underlying mechanism by introducing a condition in which a control of the landing position was added to a vertical jump task (3). However, this phenomenon was only evaluated under a single condition, where the landing position was verbally instructed, and compared to regular trials. In the present study, the mechanisms underlying this speed‒accuracy relationship were investigated by evaluating changes in jump height at required levels of accuracy when physically limiting the landing position accuracy.
METHODS:
One healthy adult subject performed each 10 trials of vertical jumps on a force plate under the following four conditions: (1) normal condition (nc); (2) 100% adjustment condition (ad100); (3) 80% adjustment condition (ad80); (4) 60% adjustment condition (ad60). Signal outputs from the force plate were digitized at 1000 Hz. From the acquired force data, the corresponding mass and 3D acceleration vectors were calculated. Then, the 3D velocity and position vectors were calculated by the numerical integration of the accelerations. From these variables, the position vectors and distances of the takeoff and landing points, as well as the jump height, were calculated. In addition, the angle from the velocity vector of the takeoff and the landing was calculated, as well as deviation from the vertical direction.
RESULTS:
Jump height decreased as the required landing accuracy condition increased (nc: 0.47±0.01 m, ad100: 0.46±0.01 m, ad80: 0.45±0.01 m, ad60: 0.43±0.01 m) (p < 0.05). The distance between the two points was calculated using the xz coordinates of the center of gravity of the landing and takeoff points for each condition (nc: 0.22±0.04 m, ad100: 0.18±0.08 m, ad80: 0.16±0.03 m, ad60: 0.10±0.04 m) (p< 0.05). These results indicate that the takeoff velocity was adjusted to improve the accuracy of the landing position, since the jump height is determined by the takeoff velocity. The deviation of the velocity vector of takeoff from the vertical direction decreased with conditions of higher required landing accuracy (nc: 3.30±1.08°, ad100: 3.75±1.73°, ad80: 2.17±1.00°, ad60: 1.75±0.90°) (p < 0.05). More vertical control of the takeoff may have improved the accuracy of the landing position.
CONCLUSION:
Even in the vertical jump task, which is usually performed with maximal effort, when the landing position was made the target of control and the level of control was varied, it was shown that as accuracy increased, the velocity (jump height) decreased. Furthermore, it was shown that accuracy could be improved by controlling the velocity vector of the takeoff in a more vertical direction.
REFERENCES:
1)Fitts, 1954
2)Woodworth, 1899
3)Murakami & Yamada, 2024