Fortuna Rafael, Groeber Martin, Seiberl Wolfgang, Power Geoffrey A, Herzog Walter
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
Department of Biomechanics in Sports, Faculty of Sport and Health Sciences, Technische Universität München, Munich, Germany.
Physiol Rep. 2017 Jun;5(12). doi: 10.14814/phy2.13279. Epub 2017 Jun 29.
The steady-state isometric force following active muscle shortening or lengthening is smaller (force depression, FD) or greater (residual force enhancement, RFE) than a purely isometric contraction at the corresponding length. The mechanism underlying these phenomena is not explained within the context of the cross-bridge theory, with few studies investigating the effects of FD and RFE in stretching-shortening cycle (SSC). The purpose of this study was to perform SSC, where the time between the end of stretch and the end of shortening was manipulated by (1) adding a pause between stretch and shortening (protocol 1) or (2) performing the shortening contraction at different speeds (protocol 2). The results show that, in protocol 1, FD was reduced for SSC with a 0-sec and 0.5-sec interval between stretching and shortening, but was the same for SSC with a 1-sec interval compared to the pure FD condition. In protocol 2, FD was reduced for SSC with shortening speeds of 30 and 60°/sec, but was the same for shortening speeds of 15 and 20°/sec compared to the pure FD condition. These findings provide evidence that stretch preceding shortening affects FD in a time- and speeddependent manner, providing new information on the potential mechanism of FD and RFE.
主动肌肉缩短或拉长后的稳态等长力比相应长度下的纯等长收缩力小（力衰减，FD）或大（残余力增强，RFE）。这些现象背后的机制在横桥理论的背景下并未得到解释，很少有研究调查FD和RFE在拉伸-缩短周期（SSC）中的作用。本研究的目的是进行SSC，其中拉伸结束与缩短结束之间的时间通过以下方式进行操控：（1）在拉伸和缩短之间添加一个暂停（方案1）或（2）以不同速度进行缩短收缩（方案2）。结果表明，在方案1中，拉伸和缩短之间间隔为0秒和0.5秒的SSC的FD降低，但与纯FD条件相比，间隔为1秒的SSC的FD相同。在方案2中，缩短速度为30°/秒和60°/秒的SSC的FD降低，但与纯FD条件相比，缩短速度为15°/秒和20°/秒的SSC的FD相同。这些发现提供了证据，表明缩短前的拉伸以时间和速度依赖的方式影响FD，为FD和RFE的潜在机制提供了新信息。
