ボールバウンシング課題の速度増加局面における動作特性の変容

Abstract

The present study aimed to examine the difference in upper limb movement characteristics between basketball players and novices during the speed-increase phase in a basketball bouncing task. Two-dimensional video analysis and electromyography were used to clarify the motor control with increase in bouncing speed. The participants were 9 college basketball players and 6 novice subjects. The basketball players had approximately 10 years of experience in playing basketball and were now in training for approximately 5 days per week in their college basketball team. The novices had learned how to play basketball in their physical education class, but the ball bouncing movement was not a familiar task for them. The subjects were instructed to synchronize their movement with an external audio signal (100 bpm), and to change the bouncing speed as quickly as possible when a LED signal was lighted. During the bouncing task, two-dimensional body kinematics (joint angular displacements) were measured using a high-speed camera at 100 frames/s. Electromyographic changes were measured by surface electromyograms (EMGs) obtained at the shoulder, elbow, and wrist muscles; the co-contraction index (CI) was calculated on the basis of the activities of the flexor and extensor muscles of each joint. We found that the amplitude of angular displacement in the elbow and wrist joints was greater in the basketball players than in the novices. In each group, EMG activities, especially those of the elbow and wrist muscles, showed different changes with increased bouncing speed. In the speed-increase phase, the wrist muscles CI in the basketball players was less than that in the novices. The results of this study indicate that basketball players bounce the ball with a greater range of motion and less joint stiffness. In contrast, novices have a more restricted range of motion and higher co-contraction in the speed-increase phase. Thus it appears that basketball players can control a ball with a longer ball contact time and lower co-contraction, and can produce a more effective bouncing movement in the speed-increase phase.