目标大小对单臂和双臂动作控制特点的影响

Effects of Target Size on Unimanual and Bimanual Control Characteristics

目的:以上肢运动学特征为出发点,针对单臂和双臂屈伸目标运动进行研究,以期了解影响双臂控制特点的因素。方法:受试者根据测试要求,在2个目标区域间快速准确地屈伸单臂(左/右臂)或双臂,并确保屈伸动作的转折点落于目标区域内。保持2个目标区域中心距离不变,通过改变2个目标区域的大小,从而形成8个不同难度系数(ID)的动作任务。一种情况下,ID以升序的方式展现给受试者;另一种情况,ID以降序的方式展现给受试者。通过使用角度传感器,记录受试者前臂屈伸目标运动的实时角度,并用多因素方差分析反应单臂控制特点的运动时间、停留时间、加速百分比和协调指数4个指标,以及反应双臂控制特点的平均相对相位和平均相对相位的变率。结果:无论测试是在升ID还是降ID的情况下,还是在单臂或双臂的情况下,在高ID下,运动时间和停留时间都相对较长,加速百分比和协调指数都相对较小;而协调指数跨越0.5的ID区域,在双臂的情况下更容易出现在低ID的区域。结论:随着ID的增加,手臂末端的运动逐渐从周期性运动转换到非连续性运动;从周期性到非连续性的这种转换对于双臂控制来说,更容易出现在低ID情况;增加难度系数虽然使双臂的耦合变得更紧密,但是并没有使双臂的协调变的更加稳定。

The purpose of this study is to understand the factors affecting the characteristics of bimanual control. The kinematic characteristics of upper extremities were studied in unimanual and bimanual aiming movements. Subjects were asked to flex and extend one or both arms between two target regions as fast and accurately as possible. They were told that the turning points in flexion and extension should fall into the target regions. The width of the target in the direction of movementwas manipulated within a trialto createIndex ofdifficulty(IDs)of 2.5 to 6.0 in 0.5 increments orto create IDsof 6.0 to 2.5 in 0.5 decrements. Two potential meters recorded the real-time angles of the subject’s forearms. The measurements include movement time,dwell time,percent time to peak velocity,harmonicity index,relative phase,and relative phase variability. Data were analyzed using analyses of variance. The results showed that,regardless of whether performances were tested in a decreasing or increasing ID condition or in a unimanual or bimanual condition,movement time and dwell time were increased,and percent time to peak velocity was reduced at the higher IDs. The harmonicity index spans the ID area of 0.5,which is more likely to occur in the low IDs for the bimanual condition. We conclude that as ID increases the end-effectors’ motion gradually switched from cyclical motion to discrete motion. The transition from cyclical motion to discrete motion is more likely to occur in low ID conditions for bimanual control. In terms of bimanual coordination,increasing the accuracy requirement resulted in a tighter but not more stable coupling between the two limbs.