Postma Dees B W, den Otter A Rob, Zaal Frank T J M
Center for Human Movement Sciences, University Medical Center Groningen, Sector F, University of Groningen, Groningen, the Netherlands.
PLoS One. 2014 Mar 26;9(3):e92392. doi: 10.1371/journal.pone.0092392. eCollection 2014.
When faced with a fly ball approaching along the sagittal plane, fielders need information for the control of their running to the interception location. This information could be available in the initial part of the ball trajectory, such that the interception location can be predicted from its initial conditions. Alternatively, such predictive information is not available, and running to the interception location involves continuous visual guidance. The latter type of control would predict that fielders keep looking at the approaching ball for most of its flight, whereas the former type of control would fit with looking at the ball during the early part of the ball's flight; keeping the eyes on the ball during the remainder of its trajectory would not be necessary when the interception location can be inferred from the first part of the ball trajectory. The present contribution studied visual tracking of approaching fly balls. Participants were equipped with a mobile eye tracker. They were confronted with tennis balls approaching from about 20 m, and projected in such a way that some balls were catchable and others were not. In all situations, participants almost exclusively tracked the ball with their gaze until just before the catch or until they indicated that a ball was uncatchable. This continuous tracking of the ball, even when running close to their maximum speeds, suggests that participants employed continuous visual control rather than running to an interception location known from looking at the early part of the ball flight.
当面对沿矢状面飞来的高飞球时，外场手需要信息来控制自己跑向拦截位置。这些信息可能在球轨迹的初始阶段就已可得，这样拦截位置就能从其初始条件预测出来。或者，这种预测信息不可得，跑向拦截位置就需要持续的视觉引导。后一种控制方式预计外场手在球飞行的大部分时间里都盯着飞来的球，而前一种控制方式则符合在球飞行的早期看球；当可以从球轨迹的第一部分推断出拦截位置时，在球轨迹的剩余部分一直盯着球就没有必要了。本研究探讨了对飞来的高飞球的视觉跟踪。参与者配备了移动眼动仪。他们面对从约20米处飞来的网球，投影方式使得有些球是可以接住的，有些则接不住。在所有情况下，参与者几乎一直用目光跟踪球，直到即将接球或直到他们表示球接不住为止。即使在接近最大速度奔跑时仍持续跟踪球，这表明参与者采用的是持续视觉控制，而不是跑向从球飞行早期就已知的拦截位置。
