My agility club has been teaching a tricks class over the summer, to raise funds so that we can buy more wing jumps. This week it was my turn to teach them a trick, and we worked on backing up on cue.
Dogs will gravitate towards the location where they have received their rewards. When you are training a back-up cue, this means that they need to be reinforced away from the handler, at the location where they have backed up to (or even slightly behind it). Rewarding the dog from your hand makes it hard to get more than a couple of steps of backing up, as the dog will want to come forward again to your hand to get its cookie.
Feeding from the hand is a deeply entrenched habit, and I had to remind them all multiple times to toss the cookies back to their dog after he had moved backwards. Once they had got the mechanics right, the dogs were much happier to leave their handlers and back up for their supper.
Old Lady with Labrador Syndrome
Every beginners agility class at my old club in Wellington seemed to contain an older woman with a food-obsessed Labrador. This dog learned the obstacles fairly quickly, but then really struggled to put them together in a sequence. It had an uncanny knack for tripping up its handler, which was scary as we trained in an indoor venue with unforgiving concrete pillars for people to crash into.