Muscle tension response to sinusoidal length perturbation: a theoretical study.

The set of kinetic equations that defines a deterministic model of muscle contraction, based on the sliding filament hypothesis in which the relative sliding velocity is an independent variable, is numerically integrated under the simulated conditions of sinusoidal length perturbation. The frequency response curve of phase angle and dynamic stiffness are in agreement with experimental curves. The resultant mean tension per cycle is lower than the unperturbed steady-state tension. The magnitude of the negative tension deviation is greater when either the amplitude or the frequency of the oscillation is increased. The tension-time curve differs from a simple sine when the perturbing frequency is in the vicinity of the stiffness minimum. These consequences are in agreement with the few experimental results that are available.