To investigate the relationship between fascicle behavior and joint torque, the fascicle behavior of the triceps surae during isometric and eccentric (30 and 60 deg/s) plantar flexion by maximal voluntary and submaximal electrical activation (MVA and SEA) was measured by real-time ultrasonography. Eccentric torque at 30 and 60 deg/s was significantly higher than isometric torque under SEA, but not under MVA. However, fascicle length did not significantly differ between isometric and eccentric trials under either condition. Therefore, the difference in developed torque by MVA and SEA cannot be explained by fascicle behavior. Under both MVA and SEA conditions, eccentric torque at 30 and 60 deg/s was equivalent. Similarly, fascicle lengthening velocities at 30 and 60deg/s did not show any significant difference. Such fascicle behavior can be attributed to the influence of tendinous tissue and pennation angle, and lead to a lack of increase in eccentric torque with increasing angular velocity.
Chino is with the Japan Institute of Sports Sciences, Tokyo, Japan; Mitsukawa, Kobayashi, and Miyoshi are with the Graduate School of Human Sciences, Waseda University, Saitama, Japan; Oda is with the Department of Physical Education and Arts Education, Hyogo University of Teacher Education, Hyogo, Japan, and the Living Matter Simulation Team, RIKEN, Saitama, Japan; Kanehisa and Fukashiro are with the Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan; Fukunaga is with the National Institute of Fitness and Sports in KANOYA, Kagoshima, Japan; and Kawakami is with the Faculty of Sport Sciences, Waseda University, Saitama, Japan.