I am having a problem and I am looking for ideas to a possible solution. I can get a good back up from the ground (he gives to the bit/or halter and moves back), but in the saddle he is very confused. I did quite a bit of ground work with this guy before getting in the saddle and didn't picture reining back as being an issue, but it is. He tenses up and resists the bit and won't budge his feet. The way I was taught to ask was to use my seat and legs to push him into a softly resistant hand so that you close the "front door", but yet are still asking for movement with your seat and legs and they figure out that the "back door" is the only option. I have just never had a horse not know how to do that. Half halts and downward transitions aren't a problem. I figure I will try having someone on the ground while I'm in the saddle to reinforce my aids, and if that helps him get it, praise him like crazy and keep practicing until I can do it without help from the ground. Does that sound like a good place to start, any other suggestions?

Dressage Misfit:

I figure I will try having someone on the ground while I'm in the saddle to reinforce my aids, and if that helps him get it

Yes, definitely do that to help him.  Some horses just "don't get it" and make the connection between the ground work and the cues from the saddle.  Or, if you have a very high fence or indoor arena wall (something that he's not going to consider jumping) that you could face him towards, just to eliminate the option of a forward direction and try your cues again.  If you're still working by yourself, you may want to place a pole on their side of him to help him stay straight, once he starts heading backwards.

Reinbacks are hard, so one step, even a half a step back, is a great start.   

This is your OTTB, right?  Reinbacks aren't usually in their repertoire!  From the ground, yes.  From the saddle, no.  

Keep up the good work!

Thank you both! And, remmer, yes, this is William the ottb and I hadn't thought of that not even being in his training previously. I did get the slightest shift of weight back to his haunches today but was a bit slow on the reward so I will have to keep on trying so he understands and gets the proper reward on time!