Abstract
Treadmill training is known to improve stepping in complete spinal cord injured animals. Few studies have examined whether treadmill training also enhances locomotor recovery in animals following incomplete spinal cord injuries. In the present study, we compared locomotor recovery in trained and untrained rats that received a severe mid-thoracic contusion of the spinal cord. A robotic device was used to train and to test bipedal hindlimb stepping on a treadmill. Training was imposed for 8 weeks. The robotic device supported the weight of the rats and recorded ankle movements in the hindlimbs for movement analyses. Both the trained and untrained rats generated partial weight bearing hindlimb steps after the spinal cord contusion. Dragging during swing was more prevalent in the untrained rats than the trained rats. In addition, only the trained rats performed step cycle trajectories that were similar to normal step cycle trajectories in terms of the trajectory shape and movement velocity characteristics. In contrast, untrained rats executed step cycles that consisted of fast, kick-like movements during forward swing. These findings indicate that spinal cord contused rats can generate partial weight bearing stepping in the absence of treadmill training. The findings also suggest that the effect of treadmill training is to restore normal patterns of hindlimb movements following severe incomplete spinal cord injury in rats.