While many kinesiological and physiological studies on sprint running in field have been made, few of them are based on multichannel electromyographic recordings. In the current experiment electromyograms were recorded mainly from the 13 muscles of the lower limb using surface electrodes,10mm in diameter, with 50m recording wire during 70m sprint running. The subjects used in the experiment were 5 male athletes. The electromyograms recorded were examined in term of functional mechanisms of the muscles. 1) Just after start, in the first and second steps, the recording side leg was grounded at the outer-forward position and extened to the outer-backward direction. The electromyographic discharge patterns in the first and second steps were remarkably different from the ones in the third and further steps. 2) The discharge patters in the third and fourth steps were almost similar to the one during the full speed term. 3) The discharge of the tibialis anterior muscle appeared just at the beginning of the swing phase. It lasted until the end of the swing phase, but at brief period of the mid-swing phase, it was depressed. And it tended to separate into two periods as the running speed increased. The faster pariod of the discharges corresponded with the dorsi flexion of the ankle joint, and the latter, with the inversion of it. The discharge of the gastrocnemius appeared at the mid-swing phase and lasted until the end of the stance phase. It worked in the fixation of the ankle joint with the tibialis anterior in the swing phase and in the plantar flexion in the stance phase. 4) The marked discharges of the vastus medialis and the rectus femoris appeared in the middle of the stance phase in the first and second steps, suggesting the active extension of the knee joint in the phase. However, in the latter half part of the stance phase, so called "kicking phase", the discharges were not observed in the full speed term. 5) The biceps femoris increased in the discharge as the running speed increased. It was also indicated that various muscles participated in the hip extension in the stance phase of the full speed term. 6) The contraction in the latter stage of the swing phase of vastus medialis, biceps femoris and gluteus maximus indicated knee and hip extension. The muscles participated in extending the thigh backward and swinging the lower leg forward. 7) The discharges of rectus femoris, gluteus medius, tensor fasciae latae, sartorius and adductor longus, observed in the early part of the swing phase, indicated the muscles participating in lifting up the thigh. 8) The discharges of the deltoideus pars clavicularis and pars spinata, participating in the arm swing, showed the reciprocal pattern.
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