Analyses of airstepping movement in adult spinal dogs

Airstepping of the hind limbs, which occurred when the adult chronic spinal dog was lifted up vertically, was analyzed by high-speed cinematography and electromyography (EMG). In the film analysis, the amplitude of the step increased with decreasing cycle period of the step. The time courses of changes in the joint angles of the hind limb throughout the step were not changed and the maximum flexion of each joint occurred in the knee, ankle and hip joint in that order at any cycle period. In the EMG analysis, alternating EMG activities of the ankle extensor and flexor, and also of the bilateral knee extensors appeared. The EMG burst durations of the knee and ankle extensors correlated closely with the cycle period of the step, although that of the ankle flexor was independent of changes of the cycle period. Since similar results were observed in analyses of treadmill locomotion in the normal and adult spinal dogs, it was thought that airstepping and treadmill locomotion were regulated by the same central pattern generator existing in the lower spinal cord.