抄録
This study examines the activity levels of the neck flexor muscles and the acceleration of the head during the ushiro-ukemi movement. The subjects were seven male expert judo players (expert group) and seven males who were not experts at judo (non-expert group). The neck flexion strength (NFS) during maximal isometric voluntary contraction (MVC) and the electromyogram (EMG) activities of the sternocleidomastoid (SCM) and scalenus (SC) of the neck flexor muscle during MVC and the ushiro-ukemi movement were determined. The rectified EMG signals during the ushiro-ukemi movement were averaged and normalized as the relative value (%EMGmax) to that during MVC. The %EMGmax values for SCM and SC used the calculated ratio of SCM/SC during the ushiro-ukemi movement.We also recorded the acceleration of the head during the ushiro-ukemi movement. No significant difference was found between the expert group and the non-expert group in NFS relative to head mass.The SCM/SC ratio was significantly higher, and the acceleration of the head was significantly lower in the expert group than in the non-expert group. The results indicate that the acceleration of the head during the ushiro-ukemi movement is influenced by the activity level of the SCM. The activity level of the SCM is one of the most important elements in learning how to perform the ushiro-ukemi movement.
