Kohei Watanabe1, Motoki Kouzaki2, Ryosuke Ando3,4, Hiroshi Akima3,5, Toshio Moritani6. 1. Laboratory of Neuromuscular Biomechanics, School of International Liberal Studies, Chukyo University, Yagotohonmachi, Showa-ku, Nagoya, 466-8666, Japan. wkohei@lets.chukyo-u.ac.jp. 2. Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan. 3. Graduate School of Education and Human Development, Nagoya University, Nagoya, Japan. 4. Japan Society for the Promotion of Science, Tokyo, Japan. 5. Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan. 6. Laboratory of Applied Physiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan.
Abstract
PURPOSE: To test the hypothesis that motor units with different axonal excitability levels are localized in specific portions of the rectus femoris (RF) muscle using transcutaneous electrical nerve stimulation. METHODS: M-waves were elicited by transcutaneous electrical nerve stimulation and detected from 24 sites along longitudinal line of the muscle. The stimulation was applied to the femoral nerve, and the current level was gradually increased. RESULTS: The central locus activation, which is calculated from the spatial distribution of M-waves, appeared at the proximal regions at low stimulation level and then moved to the middle site of the muscle with an increase in the stimulation level. The results reveal that groups of motor units activated at different stimulation levels are located in different positions in the proximal-distal muscle direction. CONCLUSION: Our results suggest that motor unit properties in proximal and other regions are not uniform within the RF muscle.
PURPOSE: To test the hypothesis that motor units with different axonal excitability levels are localized in specific portions of the rectus femoris (RF) muscle using transcutaneous electrical nerve stimulation. METHODS: M-waves were elicited by transcutaneous electrical nerve stimulation and detected from 24 sites along longitudinal line of the muscle. The stimulation was applied to the femoral nerve, and the current level was gradually increased. RESULTS: The central locus activation, which is calculated from the spatial distribution of M-waves, appeared at the proximal regions at low stimulation level and then moved to the middle site of the muscle with an increase in the stimulation level. The results reveal that groups of motor units activated at different stimulation levels are located in different positions in the proximal-distal muscle direction. CONCLUSION: Our results suggest that motor unit properties in proximal and other regions are not uniform within the RF muscle.