Active state titin’s effects have been studied predominantly in sarcomere or muscle fiber segment level and an understanding of its functional effects in the context of a whole muscle, and the mechanism of those is lacking. By representing experimentally observed calcium induced stiffening and actin-titin interaction induced reduced free spring length effects of active state titin in our linked fiber-matrix mesh finite element model, our aim was to study the mechanism of effects and particularly to determine the functionally more effective active state titin model. Isolated EDL muscle of the rat was modeled and three cases were studied: passive state titin (no change in titin constitutive equation in the active state), active state titin-I (constitutive equation involves a higher stiffness in the active state) and active state titin-II (constitutive equation also involves a strain shift coefficient accounting for titin’s reduced free spring length). Isometric muscle lengthening was imposed (initial to long length, l_m = 28.7 mm to 32.7 mm). Compared to passive state titin, (i) active state titin-I and II elevates muscle total (l_m = 32.7 mm: 14% and 29%, respectively) and active (l_m = 32.7 mm: 37.5% and 77.4%, respectively) forces, (ii) active state titin-II also shifts muscle’s optimum length to a longer length (l_m = 29.6 mm), (iii) active state titin-I and II limits sarcomere shortening (l_m = 32.7 mm: up to 10% and 20%, respectively). Such shorter sarcomere effect characterizes active state titin’s mechanism of effects. These effects become more pronounced and functionally more effective if not only calcium induced stiffening but also a reduced free spring length of titin is accounted for.

主要在肌小节或肌纤维节段水平上研究了活动状态蛋白的作用，并且在整个肌肉的背景下还缺乏对其功能作用的了解，而缺乏这些作用机理的研究。通过在我们的链接纤维-基体网格有限元模型中代表实验观察到的钙诱导的僵化和肌动蛋白-肌动蛋白相互作用诱导的活性态titin的自由弹簧长度减少效应，我们的目的是研究作用机理，尤其是确定功能上更有效的活跃状态titin模型。对大鼠离体的EDL肌肉进行建模，并研究了3种情况：被动状态titin（活动状态下titin本构方程无变化），活动状态titin-I（本构方程包含在活动状态下较高的刚度）和活动状态titin-II（本构方程还包含应变位移系数，说明了廷丁减小的自由弹簧长度）。进行等距的肌肉加长（从最初到较长的长度，1 _m  = 28.7 mm至32.7 mm）。与被动状态titin相比，（i）主动状态titin-I和II分别提高了肌肉总量（1 _m  = 32.7 mm：分别为14％和29％）和主动（1 _m  = 32.7 mm：37.5％：77.4％）。 ），（ii）活性状态titin-II还将肌肉的最佳长度转移到更长的长度（l _m  = 29.6 mm），（iii）活性状态titin-I和II限制了肌节的缩短（l _m  = 32.7 mm：分别高达10％和20％）。这种较短的肌节效应是活动状态肌动蛋白作用机制的特征。如果不仅考虑了钙引起的变硬，而且还降低了替丁的自由弹簧长度，那么这些作用将变得更加明显并且在功能上更加有效。