Isometric および eccentric な予備緊張が肘屈曲速度に及ぼす影響 : Concentric な収縮中の負荷重量および動作範囲に着目して

Abstract

This study investigated the effects of isometric and eccentric preliminary muscle contractions on elbow flexion velocity with special reference to load and range of motion during concentric contraction. Subjects were fifteen healthy males. They performed elbow flexion with maximum concentric contraction, just followed by three types of preliminary muscle contraction, i.e., resting condition (After-load method: AL), maximum isometric contraction (Isometric quick release method: IQR), and maximum eccentric contraction (Eccentric quick release method: EQR). Loads during concentric contraction were nine kinds of equivalent mass ranging from 11.4 to 556.7 kg. Comparisons of force, velocity and EMG during concentric contraction were made among three methods. Although the effect of the preliminary contraction on the elbow flexion velocity was observed, the effect of EQR was larger than that of IQR. Furthermore,the effects of both EQR and IQR were remarkable in the only early phase during concentric contraction with the lighter loads. We discussed physiological and mechanical background producing forces at the starting point and from initial to final phases during concentric contraction, since the above effects of the preliminary muscle contractions would be caused by magnitude of their forces. Consequently, it was suggested that the effects of isometric and eccentric preliminary muscle contractions were caused by the complex of positive and negative effects based on some physiologidal and mechanical factors, i.e., activntion level of muscle at the starting point, reuse of elastic energy and decrease of loss energy in early phase, and excitation and inhibition of contractile energy from initial to middle phases during concentric contraction.