Example of what Janet and I described. I described doing this with the trainer holding a ball and the client holding pressure into the ball. What Janet would do could be the same foot pattern but putting tension on a band instead of a ball. Either works.
I filmed this variation (with permission) at a training with Michol Dalcourt talking about loaded movement training. A more common warding pattern would be to push the upper body in the frontal plane while lunging the legs back in the sagittal plane. This variation with the force and the movement both in the frontal plane is more challenging than it looks! I also like any opportunity for partner work that I can include in a training session.