Effects of swimming on functional recovery after incomplete spinal cord injury in rats

One of the most promising rehabilitation strategies for spinal cord injury is weight-supported treadmill training. This strategy seeks to re-train the spinal cord below the level of injury to generate a meaningful pattern of movement. However, the number of step cycles that can be accomplished is limited by the poor weight-bearing capability of the neuromuscular system after injury. We have begun to study swimming as a rehabilitation strategy that allows for high numbers of steps and a high step-cycle frequency in a standard rat model of contusive spinal cord injury. The purpose of the present study was to evaluate the effect of swimming as a rehabilitation strategy in rats with contusion injuries at T9. We used a swimming strategy with or without cutaneous feedback based on original work in the chick by Muir and colleagues. Adult female rats (n=27) received moderately-severe contusion injuries at T9. Walking and swimming performance were evaluated using the Open-Field Locomotor Scale (BBB; Basso et al., 1995) and a novel swimming assessment, the Louisville Swimming Scale (LSS). Rats that underwent swim-training with or without cutaneous feedback showed a significant improvement in hindlimb function during swimming compared to untrained animals. Rats that underwent swim-training without cutaneous feedback showed less improvement than those trained with cutaneous feedback. Rats in the non-swimming group demonstrated little improvement over the course of the study. All three groups showed the expected improvement in over-ground walking and had similar terminal BBB scores. These findings suggest that animals re-acquire the ability to swim only if trained and that cutaneous feedback improves the re-training process. Further, these data suggest that the normal course of recovery of over-ground walking following moderately-severe contusion injuries at T9 is the result of a re-training process.