A great, FREE, full text on forward and backward walking kinematics and a possible link to central pattern generators.

“Leg kinematics during backward walking (BW) are very similar to the time-reversed kinematics during forward walking (FW). This suggests that the underlying muscle activation pattern could originate from a simple time reversal, as well…

"We concluded that the changes in muscle contributions imply that a simple time reversal would be insufficient to produce BW from FW. We therefore propose that BW utilizes extra elements, presumably supraspinal, in addition to a common spinal drive. These additions are needed for propulsion and require a partial reconfiguration of lower level common networks.”

http://jn.physiology.org/content/107/12/3385

Similar muscles contribute to horizontal and vertical acceleration of center of mass in forward and backward walking: implications for neural controlKaren Jansen, Friedl De Groote, Firas Massaad, Pieter Meyns, Jacques Duysens, Ilse JonkersJournal of Neurophysiology Published 15 June 2012 Vol. 107 no. 12, 3385-3396 DOI: 10.1152/jn.01156.2011