Urbin M A, Stodden David, Boros Rhonda, Shannon David
Auburn University-Department of Kinesiology, Auburn, AL, USA.
Motor Control. 2012 Jan;16(1):19-30. doi: 10.1123/mcj.16.1.19.
The purpose of this study was to examine variability in overarm throwing velocity and spatial output error at various percentages of maximum to test the prediction of an inverted-U function as predicted by impulse-variability theory and a speed-accuracy trade-off as predicted by Fitts' Law Thirty subjects (16 skilled, 14 unskilled) were instructed to throw a tennis ball at seven percentages of their maximum velocity (40-100%) in random order (9 trials per condition) at a target 30 feet away. Throwing velocity was measured with a radar gun and interpreted as an index of overall systemic power output. Within-subject throwing velocity variability was examined using within-subjects repeated-measures ANOVAs (7 repeated conditions) with built-in polynomial contrasts. Spatial error was analyzed using mixed model regression. Results indicated a quadratic fit with variability in throwing velocity increasing from 40% up to 60%, where it peaked, and then decreasing at each subsequent interval to maximum (p < .001, η2 = .555). There was no linear relationship between speed and accuracy. Overall, these data support the notion of an inverted-U function in overarm throwing velocity variability as both skilled and unskilled subjects approach maximum effort. However, these data do not support the notion of a speed-accuracy trade-off. The consistent demonstration of an inverted-U function associated with systemic power output variability indicates an enhanced capability to regulate aspects of force production and relative timing between segments as individuals approach maximum effort, even in a complex ballistic skill.
本研究的目的是检验在最大速度的不同百分比下，过肩投掷速度和空间输出误差的变异性，以测试冲动变异性理论所预测的倒U形函数以及菲茨定律所预测的速度-准确性权衡。30名受试者（16名熟练者，14名非熟练者）被要求以随机顺序，在距离目标30英尺处，以其最大速度的7个百分比（40%-100%）投掷网球（每个条件进行9次试验）。使用雷达枪测量投掷速度，并将其解释为整体系统功率输出的指标。使用具有内置多项式对比的受试者内重复测量方差分析（7个重复条件）来检验受试者内投掷速度变异性。使用混合模型回归分析空间误差。结果表明，投掷速度变异性呈二次拟合，从40%增加到60%时达到峰值，然后在随后的每个区间下降至最大值（p <.001，η2 =.555）。速度与准确性之间没有线性关系。总体而言，这些数据支持在熟练和非熟练受试者接近最大努力时，过肩投掷速度变异性存在倒U形函数的观点。然而，这些数据不支持速度-准确性权衡的观点。与系统功率输出变异性相关的倒U形函数的一致证明表明，即使在复杂的弹道技能中当个体接近最大努力时，调节力产生方面和各节段之间相对时间的能力增强。
