title: Robot-assisted hindlimb extension increases the probability of swing initiation during treadmill walking by spinal cord contused rats.
abstract: Training and evaluation of locomotion in animals with spinal cord injury will likely be improved with the development of techniques that increase stepping activity. We hypothesized that robot-assisted extension of the hindlimbs of spinal cord injured rats during stance would increase the probability that the swing phase of gait would be initiated. Thirty-three adult, Sprague-Dawley rats received a contusion injury to the mid-thoracic spinal cord. The animals' hindlimbs were pulled into extension using small robotic arms to pull at the ankle, as the rat stepped on either a reciprocating, robotic paw platform or a conventional treadmill belt. The animals demonstrated an increase in the probability of swing initiation with spontaneous recovery during the first 4 weeks following injury (p < 0.0001). The probability of swing initiation was found to be greater with the use of robot-assisted extension versus no extension force at the ankle (75+/-16.9% versus 38.9+/-16.6%, p < 0.001). Swing initiation occurred most frequently at a particular distance of hindlimb extension (50 mm caudal from the neutral position at stance), but was broadly tuned about this distance. These results indicate that a greater amount of stepping activity can be elicited by robot-assisted extension, thereby providing possible benefits to evaluation and training of gait following SCI.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Center for Biomedical Engineering, 4200 Engineering Gateway (E3225), University of California, Irvine, CA 92697-3975, USA. janessler@csupomona.edu
authors.forename: Jeff A
authors.initials: JA
authors.lastname: Nessler
authors.forename: Koyiro
authors.initials: K
authors.lastname: Minakata
authors.forename: Kelli
authors.initials: K
authors.lastname: Sharp
authors.forename: David J
authors.initials: DJ
authors.lastname: Reinkensmeyer
mesh_terms: D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena; D003288:Contusions / Q000503:physiopathology; D003627:Data Interpretation, Statistical; D005260:Female; D006614:Hindlimb / Q000294:innervation / Q000502:physiology*; D008959:Models, Neurological; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012371:Robotics; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D016138:Walking / Q000502:physiology*