Methods to quantify the velocity dependence of common gait measurements from automated rodent gait analysis devices.

BACKGROUND: Walking slowly is a different biomechanical task than walking quickly, thus measures of gait will be different at different velocities, such as pre/post injury. It is necessary to determine if the difference in gait measures are from the experimental changes, or simply from traveling at different speeds. NEW
METHOD: Instead of limiting this effect, we have developed techniques to embrace the velocity dependence of gait measures. By translating the pawprints into a body coordinate frame we are able to measure location of paw placement in addition to the standard gait measures.
RESULTS: At higher velocities rats have greater consistency of steps, place their forelimb initial contact more medially and anteriorly, and place their hindlimb toe off more medially and posteriorly. Interlimb phasing also becomes more consistent at higher velocities. Following a cervical spinal cord injury consistency is reduced and the velocity dependent behaviors are significantly different. COMPARISON WITH EXISTING
METHOD: Translating the coordinate frame improves the ability to measure changes in base of support following spinal cord injury. Employing a treadmill, or limiting analysis to a narrow velocity window does address the effects of velocity. We feel that measuring across all velocities is more appropriate than dictating that the animals match speeds.
CONCLUSIONS: Quantifying locomotion with automated gait analysis devices is a great way to evaluate the changes that experimental treatments provide. These new methods allow for a more appropriate way to address the confound of many gait measures being velocity dependent.