I was lunging my horse yesterday and he kept stopping and turning in when I asked him to canter, mostly when he was going right. This direction is always his bad side - he is better going to the left. He would paw the ground and he did that flehmin lip curl thing a couple times. To correct this, I made him back up. A lot. And then I asked him to go right again at a trot. After a circle I'd ask to canter. If he stopped, I repeated the process. Eventually he would canter, but only after he kicked up his heels in a little buck.
I'm thinking about having a chiropractor come out or a massage therapist, but I wanted to hear what you guys think before. I know that him doing this when I ask him to canter can be signs of pain, but it could also be him being lazy and not wanting to work.
I would only MAKE the horse back up if the horse had already chosen backing as a form of evasion. So, if the horse is backing up on its' own to avoid going forward, and you keep telling it forward, and it knows what you want but insists on going backward, THEN I might make backing up a whole lot more vigorous. Then I'd say, "well, if you want to back, then let's REALLY back up!".
But, if he stops and is just facing me, hoping to avoid work this way, I would not then choose back up. Remember what thing you are asking the horse to do. This is "Go Forward!" Keep asking. If he chooses other things, as much as possible ignore those choices and keep asking YOUR choice. Eventually, the horse will choose the right thing, and then you stop asking and let the horse "coast" forward and ease down to a stop. Yes, you want him to canter around you, but for the first few times, just getting him to go the direction you want is your objective.
So, you ask for forward AND trot, you take pressure off and allow him to "coast" forward, and he'll come down to a walk . Fine. Then ask for forward and into a canter, and when he takes the canter, allow him to go forward without chasing him. He'll come back down again. Next time, ask for forward, and MORE canter, and then ease off pressure just a bit when he canters, but see if you can get more canter out of him. Basically, you are working on transitions more than him holding the canter, because he is not wanting to take the canter in the first place.
As you work forward you ask him to stay in the canter a bit longer each time and observe him to see if he has obvious "offness".
And yes, if you are in doubt, it doesn't hurt to have him evaluated by a chiropractor of body worker.