Etnyre B R
Human Performance and Health Sciences Department, Rice University, Houston TX 77005, USA.
Percept Mot Skills. 1998 Jun;86(3 Pt 2):1211-7. doi: 10.2466/pms.1998.86.3c.1211.
Fitts' law predicts the accuracy of movement to a target decreases as the velocity of the movement increases. This speed-accuracy tradeoff has been examined under numerous conditions. During some tasks, however, increased force to nearly maximal level decreases the variability of the movement (Sherwood & Schmidt, 1980). This condition apparently produced results different from what would be predicted by Fitts' law. The purpose of the present study was to examine the effects of maximal force on dart throwing accuracy and variability. 54 subject were categorized into groups based upon their experience with dart throwing: Advanced, Intermediate, or Beginners. Each subject performed two sessions of 15 trials. Subjects were instructed to "throw normally" for one session and "throw as hard as you can" for the other session Distances from the target (triple-20 area) on the regulation dart board were measured and recorded after each of three darts was thrown. Average Error and Variable Error were calculated for each condition for each subject. The Average Error and Variable Error were greatest for the Beginner group and least for the Advanced group. For all three experience categories both Average Error and Variable Error were significantly greater when subjects performed with maximal force. The greater average error for the maximal force for all subjects suggested that the speed-accuracy tradeoff applied to this aiming task. The greater variability in accuracy with maximal force suggested a ceiling effect, which reduced variability in previous studies, was not achieved.
菲茨定律预测，随着运动速度的增加，向目标运动的准确性会降低。这种速度与准确性的权衡已经在众多条件下得到了研究。然而，在一些任务中，将力量增加到接近最大水平会降低运动的变异性（舍伍德和施密特，1980年）。这种情况显然产生了与菲茨定律预测不同的结果。本研究的目的是检验最大力量对飞镖投掷准确性和变异性的影响。54名受试者根据他们的飞镖投掷经验被分为几组：高级组、中级组或初学者组。每个受试者进行了两个阶段，每个阶段15次试验。受试者被指示在一个阶段“正常投掷”，在另一个阶段“尽你所能用力投掷”。在每次投掷三支飞镖后，测量并记录与标准飞镖靶上目标（20分区）的距离。为每个受试者的每种情况计算平均误差和可变误差。初学者组的平均误差和可变误差最大，高级组最小。对于所有三个经验类别，当受试者以最大力量进行投掷时，平均误差和可变误差都显著更大。所有受试者在最大力量下更大的平均误差表明速度与准确性的权衡适用于此瞄准任务。最大力量下准确性的更大变异性表明，在先前研究中降低变异性的上限效应并未实现。
