The stride cycle of the cat: the modelling of locomotion by computerized analysis of automatic recordings.

The present study gives a general description of the locomotor patterns of the intact cat. Overground and treadmill locomotion were studied by means of automatic recordings of limb movements, ground reaction forces and electromyograms. The data processing and automatic recording techniques which were used are described; one recording technique is based on a television system, another on the Selspot I system. The data were processed and analysed interactively with a computer, which allows a 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 electromyographic activity in different muscles. No element of the stride cycle was found to be constant: 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 of the swing and flexion phases and they all appear to be 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 first extension phase of knee and ankle decrease, whereas 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 was found to remain comparatively constant. There is a correlation between hip, knee and ankle joint angles at touch-down, which was found to be of importance for the precise positioning of the foot.(ABSTRACT TRUNCATED AT 400 WORDS)