Kinematics of Locomotor Movements in Rats in 7-Day Unweighting

Abstract

The aim of the present work was to study the dynamics of changes in the sensorimotor control of gait in conditions of unweighting of the hindlimbs. Experiments were performed on rats in which the kinematics of locomotor movements were evaluated before, during, and after keeping the hindlimbs in the Morey-Holton antiorthostatic position. Locomotion on the treadmill after unweighting showed increases in extension at the ankle and knee joints. Analysis of the dynamics of changes in the kinematic parameters of locomotor movements in the unsupported position revealed progressive increases in extension of the knee and ankle joints, though there was a decrease in extension at the hip joint during the seven days of unweighting. This corresponded to the forced position of the hindlimbs on passive hanging, which was characterized by hyperextension of the knee and ankle joints, though with hyperflexion of the hips. These data lead to the conclusion that stable dynamics of changes in gait kinematics characterizing the operation of spinal neural networks in the central locomotor generator responsible for forming the motor pattern can be produced by progressive reorganization of the system of proprioceptive connections in conditions of the altered configuration of body posture and limb joints during unweighting.