Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan.
Faculty of Kinesiology, The University of Calgary, 2500 University Drive, NW, Calgary, AB T2N 1N4, Canada.
J Biomech. 2021 Jan 22;115:110136. doi: 10.1016/j.jbiomech.2020.110136. Epub 2020 Nov 21.
It has been suggested that residual force enhancement (RFE) contributes to the work enhancement observed in stretch-shortening cycles (SSC). Based on recent findings that RFE was preserved in the reduced force state, one may speculate that the SSC effect may be preserved in the reduced force state as well. The purpose of this study was to examine the magnitude of the SSC effect in inhibited skeletal muscle force states. Normal and inhibited force conditions were analyzed using skinned rabbit soleus fibres (N = 18). The inhibited force condition was achieved by adding 2,3-Butanedione monoxime into the activating solution. For both conditions, a SSC test and a pure shortening test were performed. In the SSC tests, fibres were activated at an average sarcomere length of 2.4 μm, and then stretched to 3.0 μm. Immediately after the end of the stretch, fibres were shortened to 2.4 μm. In the pure shortening tests, fibres were activated at an average sarcomere length of 3.0 μm and then shortened to 2.4 μm. The relative increase in mechanical work in the shortening phase of the SSC compared to the pure shortening condition was defined as the SSC effect index, and the magnitude of the SSC effect was compared between the normal and the inhibited force condition. The SSC effect was greater in the inhibited compared to the normal force condition (p < 0.001). We conclude that the SSC effect is at least in part preserved in the reduced force state.
有人认为残余力增强(RFE)有助于解释伸展-缩短循环(SSC)中观察到的力增强。基于最近发现 RFE 在减小力状态下得以保留,人们可能推测 SSC 效应在减小力状态下也可能得以保留。本研究旨在探讨抑制性骨骼肌力状态下 SSC 效应的幅度。使用去皮兔比目鱼肌纤维(N=18)分析正常和抑制力条件。抑制力条件是通过在激活溶液中添加 2,3-丁二酮单肟来实现的。对于两种条件,均进行了 SSC 测试和纯缩短测试。在 SSC 测试中,纤维在平均肌节长度为 2.4 μm 的情况下被激活,然后拉伸至 3.0 μm。在拉伸结束后立即,纤维缩短至 2.4 μm。在纯缩短测试中,纤维在平均肌节长度为 3.0 μm 的情况下被激活,然后缩短至 2.4 μm。与纯缩短条件相比,SSC 缩短阶段的机械功相对增加定义为 SSC 效应指数,并比较正常和抑制力条件之间的 SSC 效应幅度。与正常力条件相比,抑制力条件下的 SSC 效应更大(p<0.001)。我们得出结论,SSC 效应至少在一定程度上在减小力状态下得以保留。