The influence of velocity of length change on tension development in skeletal muscle: Model calculations and experimental results

Abstract

Force responses obtained during constant velocity length changes on skeletal muscle tissue are simulated by means of two cross-bridge models proposed by Huxley and Simmons (1971, Nature 233, 533–538) and by Julian et al. (1974, Biophys. J. 14 546–562). An implicit method was used for the numerical approximation in the simulations. The simulated force transients due to constant velocity length changes are found to be in qualitative agreement with re-investigated experimental results obtained from the whole sartorius muscle of the frog. A non-linear tension transient is observed, dependent both on amplitude and on velocity of release revealing an inflexion which gives the transient a shoulder shape. When velocity is increased the inflexion occurs earlier and at a lower tension value. A non-linear transient is observed during stretches performed at moderate velocities. Force responses are found to deviate concavely downwards from a linear time course. Simulations, however, predict a rather linear tension transient for comparable velocities. Implications of the experimental findings are discussed for both models.