Laboratory "Movement, Interactions, Performance" (EA 4334), Faculty of Sport Sciences, University of Nantes, Nantes, France.
Laboratory "Sport, Expertise and Performance" (EA 7370), Research Department, French Institute of Sport (INSEP), Paris, France.
Scand J Med Sci Sports. 2018 Apr;28(4):1361-1370. doi: 10.1111/sms.13043. Epub 2018 Jan 30.
We investigated the effects of the initial length of the muscle-tendon unit (MTU) and muscle pre-activation on muscle-tendon interactions during plantarflexion performed at maximal velocity. Ultrasound images of gastrocnemius medialis were obtained on 11 participants in three conditions: (a) active plantarflexion performed at maximal velocity from three increasingly stretched positions (10°, 20°, and 30° dorsiflexion), (b) passive plantarflexion induced by a quick release of the ankle joint from the same three positions, and (c) pre-activation, which consisted of a maximal isometric contraction of the plantarflexors at 10° of dorsiflexion followed by a quick release of ankle joint. During the active condition at maximal velocity, initial MTU stretch positively influenced ankle joint velocity (+15.3%) and tendinous tissues shortening velocity (+37.6%) but not the shortening velocity peak value reached by muscle fascicle. The muscle fascicle was shortened during the passive condition; however, its shortening velocity never exceeded peak velocity measured in the active condition. Muscle pre-activation resulted in a considerable increase in ankle joint (+114.7%) and tendinous tissues velocities (+239.1%), although we observed a decrease in muscle fascicle shortening velocity. During active plantarflexion at maximal velocity, initial MTU length positively influences ankle joint velocity by increasing the contribution of tendinous tissues. Although greater initial stretch of the plantarflexors (ie, 30° dorsiflexion) increased the passive velocity of the fascicle during initial movement, its peak velocity was not affected. As muscle pre-activation prevented reaching the maximal muscle fascicle shortening velocity, this condition should be used to characterize tendinous tissues rather than muscle contractile properties.
我们研究了肌肉-肌腱单位（MTU）的初始长度和肌肉预激活对最大速度下进行的跖屈运动中肌肉-肌腱相互作用的影响。在三种情况下，对 11 名参与者的比目鱼肌内侧获得了超声图像：（a）从三个逐渐伸展的位置（背屈 10°、20°和 30°）以最大速度进行主动跖屈，（b）从相同的三个位置通过快速释放踝关节进行被动跖屈，以及（c）预激活，包括在背屈 10°时进行最大等长跖屈肌收缩，然后快速释放踝关节。在最大速度的主动条件下，初始 MTU 拉伸正向影响踝关节速度（+15.3%）和腱组织缩短速度（+37.6%），但不影响肌纤维束达到的缩短速度峰值。在被动条件下，肌纤维束缩短；然而，其缩短速度从未超过主动条件下测量到的峰值速度。肌肉预激活导致踝关节（+114.7%）和腱组织速度（+239.1%）显著增加，尽管我们观察到肌纤维束缩短速度下降。在最大速度的主动跖屈中，初始 MTU 长度通过增加腱组织的贡献来正向影响踝关节速度。虽然更大的跖屈肌初始拉伸（即背屈 30°）增加了初始运动中肌纤维束的被动速度，但它的峰值速度不受影响。由于肌肉预激活阻止达到最大肌纤维束缩短速度，因此应使用这种情况来表征腱组织，而不是肌肉收缩特性。
