Toru Oshima, Kiyoshi Toriumi, Tomohiko Fujikawa, and Noboru Momose

Abstract:
We studied the effects of the lower leg bi-articular muscle in vertebrates in jumping. We used the proposed Jumping Jack model in computer simulation to analyze the impact of bi-articular muscle on postural jumping stability, energy transition caused by postural change, and the relationship between the ground reaction force and the center of gravity. We made a trial model and measured the jumping posture, ground reaction force, and jumping height to verify simulation results. The bi-articular muscle adjusted the ground reaction force so that the line of action invariably passed near the center of gravity and the conversion of elastic energy to rotational kinetic energy was suppressed, leading to a stable posture after takeoff.

Keywords: lower leg, jumping, bi-articular muscle, jumping posture, ground reaction force