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{Hw Vol. 9, No. 2, pp. 40-46 (2007)

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Evaluation of Muscular Function by Muscle Fiber Conduction Velocity during Static and Dynamic Contractions of Biceps Brachii Muscle

Kazuyuki MITO, Osamu ANZAI, Kenichi KANEKO, Kazuyoshi SAKAMOTO and Yutaka SHIMIZU

Before using surface electromyogram (EMG) variables such as muscle fiber conduction velocity (MFCV) as indicator of muscular function during dynamic exercises, it is necessary to determine the influence of the joint angle, contraction type, and contraction speed on the EMG variables. The aim of this study is to elucidate these factors during dynamic exercises. Ten healthy male volunteers performed static (isometric) and dynamic (concentric and eccentric) exercises at elbow joint angle from 40 to 140 during 20% of maximum voluntary contraction (MVC). For the dynamic exercises, contraction speed was set at 10/s and 20/s. Surface EMG signals were measured by using a 13 channel surface electrode array from biceps brachii muscle. The innervation zone was observed at the midpoint of the muscle belly during elbow joint angle of 110, and its location shifted to proximal side of muscle depending on an increase of elbow joint angle (i.e., a decrease of muscle length). The values of MFCV and EMG amplitude (RMS) were significantly increased depending to a decrease of the muscle length. For the influence of contraction type, the MFCV and RMS showed high in each elbow joint angle in order of the concentric contraction, isometric contraction and eccentric contraction. For the increase of contraction speed, the MFCV and RMS increased in the concentric contraction and decreased in the eccentric contraction. These results are useful to evaluate the muscular function during dynamic exercises.

Key words: EMG, Muscle Fiber Conduction Velocity , Dynamic Exercise, Biceps Brachii