Abstract: The forelimb of German Shepherd Dog (GSD), a land quadruped animal, was selected as the subject, and the kinematical characteristics of each joint in for-lower limb under various gaits in the foot-ground impact phase were analyzed using optical three-dimensional motion capture technology. The focus is to reveal how does each fore-lower limb joint adjust and adapt to the ground impact. The analyses of joint movement sequence and joint angle variations show that GSD employs the coordination of multi-joint flexion motion of the fore-lower limb to buffer ground reaction force. Compared with metacarpal-phalangeal joint, the humeral joint, cubital joint and carpal joint of GSD play more important roles in ground impact absorption; while, the flexion motion of these three joints function in different contact phases. The flexion of carpal joint happens first, then the humeral joint, and finally the cubital joint. This may show that the coordination of multi-joint flexion of GSD has spatio-temporal characteristics. This study also finds that the initial contact angle between ground and GSD finger increases with the ground impact force. This adaptive adjustment may help GSD to prolong the cushion time during foot-ground impact phase, thus, decreasing the strength of ground reaction force.

Key words: engineering bionics, biomechanics, canine animal, joint angle, flexion motion, buffering