General organization of the locomotor control system in the cat

This chapter focuses on the idea that during locomotion, each of the four limbs is driven by its individual control mechanism, which is relatively independent of the controllers for the other limbs. This idea emerged from the observation that, under certain conditions, the rhythms of stepping in different limbs may differ from each other. Divergence of rhythms of individual limbs was later observed by other investigators when the animal walked on a treadmill with split belts. Thus, the basic principle of the control of locomotion in walking animals, that is a considerable autonomy of the individual limb controllers, is common for different species – from crustaceans and insects to mammals. A detailed analysis of the motor pattern of the hind limb of the cat was carried out by a number of investigators. The step cycle in the cat consists of two principal parts, the stance (or support) phase and the swing (or transfer) phase. The three main joints (hip, knee, and ankle) of the hind limb perform considerable flexion–extension movements during the step cycle. To increase the speed of locomotion, there are two principal ways: to increase the frequency of stepping and to increase the amplitude of the stepping movements.