During virtual stepping, the robots were attached to the metatarsus, which yielded more consistent stepping than attaching to the toes or lower shank.
The tendency toward in-phase hopping on the virtual treadmill may be related in part to inertial loading of the metatarsus during swing by the robot.
The virtual treadmill configuration was similar, but with the conveyor removed and the robots attached to the rat's metatarsus.
In the virtual treadmill configuration, the robots were attached at the metatarsus, and the rats stepped on a haptically simulated treadmill.
Attachment to the metatarsus and lower shank was achieved using the same small cuffs as for the physical treadmill.
It was found that stepping was difficult to elicit with the toe or lower shank attachment locations, but that the rats could step with the robots attached at the metatarsus.
However, the hindlimb joint trajectories of the rat are such that the metatarsus moves through a greater distance horizontally and vertically than the lower shank during stepping.
This allows support to be placed where necessary, especially in the forefoot (metatarsus and toes) and heel.
