Christou Evangelos A, Carlton Les G
Department of Kinesiology, University of Illinois at Urbana-Champaign, USA.
Med Sci Sports Exerc. 2002 Nov;34(11):1773-8. doi: 10.1097/00005768-200211000-00013.
This study examined the ability of 10 young (25.3 +/- 2.8 yr) healthy individuals to control knee-extension force during several discrete concentric and eccentric contractions.
Subjects performed maximal and submaximal tasks on a KIN-COM isokinetic dynamometer. The submaximal tasks were to match a force-time parabola with a time to peak force of 200 ms at five target-forces (50, 100, 150, 200, and 250 N).
Mean peak force produced by the subjects at each target-force during concentric and eccentric contractions was similar. Mean time to peak force, however, was much shorter for eccentric contractions and was not influenced by increases in the level of force. The standard deviation (SD) and coefficient of variation (CV) of peak force was greater during eccentric compared with concentric contractions. The SD of time to peak force was greater for concentric contractions; however, when normalized to the mean time to peak force produced (CV), eccentric contractions were more variable.
Results provide evidence that even in young adults the control of motor output is different for eccentric compared with concentric contractions.
本研究考察了10名年轻（25.3±2.8岁）健康个体在几次离散的向心和离心收缩过程中控制膝关节伸展力的能力。
受试者在KIN-COM等速测力计上进行最大和次最大任务。次最大任务是在五个目标力（50、100、150、200和250 N）下，使力-时间抛物线与峰值力时间为200 ms相匹配。
受试者在向心和离心收缩过程中，每个目标力下产生的平均峰值力相似。然而，离心收缩时达到峰值力的平均时间要短得多，且不受力水平增加的影响。与向心收缩相比，离心收缩时峰值力的标准差（SD）和变异系数（CV）更大。向心收缩时达到峰值力时间的SD更大；然而，当以产生的峰值力平均时间进行归一化（CV）时，离心收缩的变异性更大。
结果表明，即使在年轻人中，离心收缩与向心收缩相比，运动输出的控制也有所不同。
