David S.K. Magnuson1, Rebecca Smith1, Edward H. Brown1, Gaby Enzmann1, Claudia Angeli2, Peter M. Quesada3, Darlene A. Burke4
1Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky,
2Frazier Rehabilitation Institute, Jewish Hospital Louisville, Kentucky
3Department of Mechanical Engineering, Speed School of Engineering University of Louisville, Louisville, Kentucky
4Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, Louisville, Kentucky
Tóm tắt
Background. The authors have shown that rats can be retrained to swim after a moderately severe thoracic spinal cord contusion. They also found that improvements in body position and hindlimb activity occurred rapidly over the first 2 weeks of training, reaching a plateau by week 4. Overground walking was not influenced by swim training, suggesting that swimming may be a task-specific model of locomotor retraining. Objective. To provide a quantitative description of hindlimb movements of uninjured adult rats during swimming, and then after injury and retraining. Methods. The authors used a novel and streamlined kinematic assessment of swimming in which each limb is described in 2 dimensions, as 3 segments and 2 angles. Results. The kinematics of uninjured rats do not change over 4 weeks of daily swimming, suggesting that acclimatization does not involve refinements in hindlimb movement. After spinal cord injury, retraining involved increases in hindlimb excursion and improved limb position, but the velocity of the movements remained slow. Conclusion. These data suggest that the activity pattern of swimming is hardwired in the rat spinal cord. After spinal cord injury, repetition is sufficient to bring about significant improvements in the pattern of hindlimb movement but does not improve the forces generated, leaving the animals with persistent deficits. These data support the concept that force (load) and pattern generation (recruitment) are independent and may have to be managed together with respect to postinjury rehabilitation.
