This is very intriguing, do you mind me asking what you use the back up for. We have only done the basic obedience so I haven't heard of this before.
Let me see: Often times Earnhardt is blocking the entrance door from the back yard,and if I want to go in before him,I simply tell him to "back it up". Or if I am going out,and he is already out there..when I open up the door I say..back it up~He's big,and takes up the whole door entrance. I feel its only a part of teaching them manners,as I will not get run over by a stampede of dogs.
I can get him to back it up,and with a hand signal even from a distance.He used to do it often as when he was really young,he was trained with a person that would do field trials,and he needed to understand what was being communicated to him by hand signals.nothing more irritating than to have a handler yelling directions to a dog,as they got close to a decoy.He may be rusty on some signals,but that one he has never forgotten,
Sometimes these guys will follow me into the laundry room,and there is only so much room,especially when all 3 decide to come in and check out the dirty laundry baskets...I just tell them..back it up. It's quite funny really to see all 3 simply put it in reverse.Cause there is no room to actually turn around.
I practice with Trapp & Jasper,using narrow spaces to back it up,it gets them in touch with thier rear ends & legs,making them work in what I feel is not a totally natual movement for any dog.
In probably an agility dog,or one that does freestyle events,it could in my opinion be very useful.Just my two pence~