I was working some fall ball today, and a pitcher asked me about the "double leg pump" move. In the windup, the pitcher gets on his pivot foot, raises his knee as he reaches his balance point, drops the foot as though coming to the plate, then raises the knee upward again, then delivers the pitch. I remembered the video "2019 Video Bulletin #7 - April 19, 2019" on NCAA Central Hub on Arbiter, and told him it was illegal, but after rewatching the video, I am uncertain if it's illegal because