Evaluation of a self-consistent method for calculating muscle parameters from a set of isokinetic releases.

A new method for calculating parameters describing the force-velocity relationship of the contractile element and the force-extension relationship of the series elastic element of skeletal muscle from a set of isokinetic release contractions is evaluated using experimental and numerical techniques. The method calculates from the set of isokinetic releases those force-velocity and force-extension relationships that give a self-consistent description of the data set. The self-consistent calculation method is applied to data obtained from the gastrocnemius medialis muscle of the rat, since for such an animal model both relationships can be independently derived from a set of isotonic release contractions. For the two animals studied, the force-velocity and force-extension relationships calculated by the self-consistent method were in good agreement with the ones derived from isotonic releases performed on the same muscle. The statistical properties of the estimates obtained by the calculation method were investigated using a Monte Carlo technique. The method was found to yield results which were biased by less than 2% and which possessed a coefficient of variation smaller than 5%. These findings indicate that the proposed calculation method can be a useful tool for determining the contractile properties of skeletal muscle as reflected in the force-velocity and force-extension relationships.