Herzog W, Leonard T R
Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.
J Biomech. 2000 May;33(5):531-42. doi: 10.1016/s0021-9290(99)00221-3.
The purpose of this study was to determine the history dependence of force production during and following stretch-shortening and shortening-stretch cycles in mammalian skeletal muscle. Thirty-three different isometric, stretch, shortening, stretch-shortening and shortening-stretch experiments were preformed in cat soleus (n=8) using previously established methods. Stretch-shortening and shortening-stretch cycles are not commutative with respect to the isometric forces following the length changes. Whereas force depression following shortening is virtually unaffected by previous stretching of the muscle, force enhancement following stretch depends in a dose-dependent manner on the amount of muscle shortening preceding the stretch. The history dependence of isometric force following shortening-stretch cycles can conveniently be modelled using an elastic (compressive and tensile) element that engages at the length of muscle activation. Such an "elastic" mechanism has been proposed by Edman and Tsuchiya (1996) (Edman, K.A. P., Tsuchiya, T., 1996. Strain of passive elements during force enhancement by stretch in frog mucle fibres. Journal of Physiology 490. 1, 191-205) based on experimental observations, and has been implemented theoretically in a rheological model of muscle (Forcinito et al., 1997) (Forcinito, M., Epstein, M., Herzog, W., 1997. Theoretical considerations on myofibril stiffness. Biophysics Journal 72, 1278-1286). The history dependence of isometric force following stretch-shortening cycles appears independent of the stretch preceding the shortening, except perhaps, if stretching occurs at very high speeds (i.e. 6-10 times fibre length per second). The results of this study are hard to reconcile with the two major mechanisms associated with history dependence of force production: sarcomere length non-uniformity (Edman et al., 1993) and stress-induced cross-bridge inhibition (Maréchal and Plaghki, 1979) (Maréchal, G., Plaghki, L., 1979. The deficit of the isometric tetanic tension redeveloped after a relase of frog muscle at a constant velocity. Journal of General Physiology 73, 453-467). It appears that studying the history dependence of force production under more functionally relevant conditions than has been done to date may provide new information that contributes to our understanding of possible mechanisms associated with force depression and force enhancement following muscular length changes.
本研究的目的是确定哺乳动物骨骼肌在拉长-缩短和缩短-拉长周期期间及之后力量产生的历史依赖性。使用先前建立的方法对猫比目鱼肌（n = 8）进行了33种不同的等长、拉伸、缩短、拉长-缩短和缩短-拉长实验。就长度变化后的等长力而言，拉长-缩短和缩短-拉长周期是不可交换的。虽然缩短后的力量下降实际上不受肌肉先前拉伸的影响，但拉伸后的力量增强以剂量依赖的方式取决于拉伸前肌肉缩短的量。缩短-拉长周期后等长力的历史依赖性可以方便地用一个在肌肉激活长度处起作用的弹性（压缩和拉伸）元件来建模。Edman和Tsuchiya（1996年）（Edman, K.A. P., Tsuchiya, T., 1996. Strain of passive elements during force enhancement by stretch in frog mucle fibres. Journal of Physiology 490. 1, 191 - 205）基于实验观察提出了这样一种“弹性”机制，并在肌肉的流变学模型中从理论上进行了实现（Forcinito等人，1997年）（Forcinito, M., Epstein, M., Herzog, W., 1997. Theoretical considerations on myofibril stiffness. Biophysics Journal 72, 1278 - 1286）。除了可能在非常高的速度（即每秒6 - 10倍纤维长度）下发生拉伸外，拉长-缩短周期后等长力的历史依赖性似乎与缩短前的拉伸无关。本研究的结果很难与与力量产生的历史依赖性相关的两个主要机制相协调：肌节长度不均匀性（Edman等人，1993年）和应力诱导的横桥抑制（Maréchal和Plaghki，1979年）（Maréchal, G., Plaghki, L., 1979. The deficit of the isometric tetanic tension redeveloped after a relase of frog muscle at a constant velocity. Journal of General Physiology 73, 453 - 467）。看来，在比迄今为止更具功能相关性的条件下研究力量产生的历史依赖性可能会提供新的信息，有助于我们理解与肌肉长度变化后的力量下降和力量增强相关的可能机制。
