All I can say is that if you are thinking of taking a shot at a running deer, then you are doing the right thing by practicing it! It is surprising at how much a deer can move even at walkiung speed before the arrow gets to it no matter how fast you are shooting. Personally, I will shoot at a slow paced walk, but that is about it. One, time I shot at a deer that was standing still grazing (30 yards), and just as I was at the point of no return on the release, the deer took a step. Luck for me that as the deer stepped it also turned slightly quartering away. It turned my double lung broadside shot into a liver, single lung. I waited 5 hours before tracking and found the buck dead in a bed. But I learned a lot from the shot. And it was a very long five hours to wait. BTW, I was shooting carbons and a muzzy 75 grain head at the time FPS around 290.