What are syntactic and semantic cues?

What should I do with my horse to get him to stop bucking when I give him cues?

• I have a 17h paint horse (yes, he's a freak of nature. but he IS a registered paint) and I've been trying to teach him flying lead changes. I know he can do them (hes pulled like three in a row before when he ran out of a jump), it's just about me getting my cue across. I've been told that I should keep my inside leg on the girth, and my outside one a little behind and then when going down a diagonal I should swap them. Only thing is, this requires my horse to feel/acknowledge the presence of my heels. He HATES heels. He throws fits and bucks and basically just goes crazy when I use my heels! I don't use spurs or anything like that. Just the usual tack (saddle, bridle, kimberwick bit) Is there anyway to break this crazy habit from my horse? I've considered trying to find an alternative way to ask for a flying lead, but I need my heels for other things like jump cues, and other dressage commands, so I'd rather just conquer his hatred of them. Any suggestions?? p.s. I ride English if that factors into you response.

• Answer:

  First, you shouldn't be using your heels as much as your whole inside leg. You revert to your heels only when you don't get a response off of your leg pressure or when you are doing very advanced movements that sometimes need that little bit of encouragement. Second, if you don't have a trainer you need one. It may be that you aren't asking just right or your horse isn't balanced and prepared when you do ask. Google videos. I can't find the one I wanted to post. It will help.