THE STRIDE CYCLE OF THE CAT - THE MODELING OF LOCOMOTION BY COMPUTERIZED ANALYSIS OF AUTOMATIC RECORDINGS

Google Scholar
  • 1 January 1983
    • journal article
    • review article
    • Vol. 521, 1-75
Abstract
A general description of the locomotor patterns of the intact cat is given. Overground and treadmill locomotion were studied by means of automatic recordings of limb movements, ground reaction forces and electromyograms [EMG]. One recording technique is based on a television system, another on the Selspot I system. The data were processed and analyzed interactively with a computer, allowing statistical analysis of many strides in a fast and accurate way. The amplitudes and time course of movements in different joints and different limbs were studied at different velocities of locomotion and correlated to each other and to parameters such as the onset and termination of EMG activity in different muscles. The amplitudes of joint angles and limb excursions as well as the durations of the different phases of the stride cycle can be adapted to maintain an appropriate coordination between the limbs. The durations of all phases of the stride cycle decrease with increasing speed of locomotion. The durations of the support and extension phases change proportionally more than those of the swing and flexion phases and they all are linearly related to the stride cycle duration. The relations of the flexion duration with the stride cycle duration for the different joints are usually different from each other, and after a disturbance of the movements of a forelimb the duration of knee and ankle flexion of the homolateral limb can increase and the 1st extension phase of knee and ankle decrease. They usually increase or decrease together. This further supports the hypothesis that every joint is controlled by a flexion and extension unit pattern generator. The amplitude of the joint angle excursions during the different phases of the stride cycle are better controlled than the absolute joint angles at the onset and termination of these phases. The position of the toe at touch-down was studied at different velocities of locomotion and remains comparatively constant. There is a correlation between hip, knee and ankle joint angles at touch-down, which was important for the precise positioning of the foot. During alternating locomotion, such as walking and trotting, all events of the stide cycle are shifted approximately half a cycle with respect to the corresponding events on the contralateral side. The limbs remian coordinated even when large asymmetries in the stride cycle are induced by letting the left and right pairs of limbs locomote at different speeds on 2 separate treadmill belts. An event just preceding the support phase or at its onset is always shifted approximately half a cycle with respect to the corresponding event on the contralateral side during split belt locomotion with a 1:1 rhythm. At a certain speed difference between the 2 belts, the asymmetries become too large and the limbs stepping on the belt with the higher speed will take 2 strides when the limbs stepping on the slower belt take only one. The 2 strides of the limb stepping on the fast belt are asymmetric with respect to limb positioning, time course of different phases and EMG activity. The coordination between forelimbs and hindlimbs is not very strict. Intervals may change gradually with increasing speed of locomotion and no fixed values were observed. At the same velocity of locomotion the same interval could vary considerably between trials.