Abstract
To clarify the mechanism of the difference between the load-velocity relation of the human elbow flexors determined by the quick release method and that determined by the after-load method, the relations were calculated from a mathematical model for the human elbow flexion. In this model, the biceps brachii was considered equivalent to the elbow flexors. This equivalent muscle was composed of two components, i.e. the contractile one obeying Hill's characteristic equation and the seriese elastic one. The inputs to this model were the states of the muscle excitement. In the quick release method, the state was consistent and full throughout the muscle contraction. In the after-load method, the state changed linearly from zero at the onset of the contraction to a maximum at 70 ms after the onset, thereafter it kept maximal. The velocities calculated in the after-load method were not greater than those in the quick release method at the loads which corresponded to 0, 10, 20, 30, 40, 50 and 60% of the maximum isometric strength. This result was not compatible with the result of the human elbow flexion reported by Kaneko that the velocity in the after-load method was greater than that in the quick release method when the load was equal to or greater than the load which corresponded to 10% of the maximum isometric strength. According to the result from the mathematical model, it is assumed that there was a difference between the pattern of the muscle excitement in the human elbow flexion and that in the model, or that in the human elbow flexion, the level of the muscle excitement in the quick release method was lower than that in the after-load method when the velocity was measured.
