Look, can we agree that there is some acceleration when you throw the arm back? I think we can. If you want to reference K'ON's post, if you need proof. What I'm saying is you should time the extending of the arm with the lunge, so that the arm throw back adds to the acceleration of the lunge. Once the back arm is straight (when the 'hand' is pulling back on the 'sphere'), the lunge is over. The double-benefit of this is that after my lunge is over I get to use the "pull back" argument for the recovery.