The locomotion of the low spinal cat. II. Interlimb coordination

TLDR

The study examined hindlimb coordination in 14 chronic spinal kittens by analyzing muscle activity and movement patterns during treadmill locomotion after thoracic spinal cord transection. The kittens displayed alternating gaits at low speeds and increasingly simultaneous limb activation at higher speeds, could walk at different belt velocities while maintaining a common rhythm up to a 2–3‑fold speed difference, and even performed multiple steps on the fast belt per slow‑belt step, indicating that all step‑cycle phases are modifiable and multiple spinal mechanisms coordinate limb movements.

Abstract

The interaction of the two hindlimbs were investigated by an analysis of the muscular activity and the movements in 14 chronic spinal kittens during treadmill locomotion (i.e. in kittens subjected to a transection of the spinal cord (Th 10–12 ) one or two weeks after birth). At low speed the limbs were alternating (walk or trot). At higher they were activated more simultaneous, as during gallop. The two limbs could walk at different velocities, as during walking in a circle, when the two belts of the treadmill were driven at different speeds. The duration of the support phases was mainly influenced by the speed of the belt on which the limb was walking. The limbs could still maintain a common rhythm up to a two or three fold speed difference, as the flexion or the first extension phase of the limb walking on the “fast” belt was prolonged and the flexion phase of the “slow limb” was shortened. At extreme speed differences the limb on the “fast belt” performed 2, 3 and even 4 steps during one stepcycle of the “slow limb”. The placement of the feet was found to maintain the most stable relationship during alternating gaits at different speed differences. It is concluded that all phases of the step cycle are modifiable and that there are several mechanisms coordinating the limbs within the spinal cord.