heavy on the forehand...

My OTTB isn't totally engaging her hind end and gets a little heavy on the forehand at times.
I've been trying vary our workouts with things to help but I'm running out of ideas...
What are some exercises you do to keep your horse off the forehand?

Transitions, transitions and transitions. Mix in a lot of bending and suppling exercises. It works for my TB. A fun one I've been doing is, working trot on diagonal, transition to shorter collected trot when approaching the short side. Overbend during this phase. Halfway through short side, transition down to working energetic walk, coming out of corner do several steps of shoulderfore or simply overbend if he doesn't know shoulderfore yet. Come off rail and transition back up to working trot and repeat it all in the other direction. It's basically a flat figure 8 with transitions and bending mixed in.

Thanks! I'm heading to the barn to ride her in a few so I'll definitely try that one today.

I agree with puck re: transitions. One thing to note is don't always do 'lengthening on the long side, shorten on the short side' as some horses anticipate it and start to blast out of the corner. Mix it up a bit.

Additionally, if you have any hills in the area, lots of trotting up and down hills can really build up your horse's butt.

Rein-back can really help a horse sit on its butt a bit more. Don't over do it, but it's useful in the correct amount.

Yeah, I got burned on the rein back. I started using it too much and my TB quickly learned to use it to not go forward when he doesn't feel like working. He also stopped standing still at the halt. Instead he'd do a nice halt and then back up a few steps. I can just see him backing his way out of the dressage arena while I'm trying to salute!

^Ugh. One of the hardest things about training horses is that you have to be smarter than they are. I don't know about you, but I find that can be a problem for me (especially with the TBs).

Another thing is to teach your horse TOF before the rein back. Once the 'back up' button is installed, any combination of leg and hand translates to "I want you to back up". Kind of like that saying where everything looks like a nail when all you have is a hammer. Horse gets confused and does the only thing it knows how to do. Total nightmare.

You should of been there when I taught him to leg yeild. He got so used to me going down the quarterline or centerline and then yeildling, that he forgot how to go straight. Any slight unintentional cue from me had him going sideways. I've had to omit if from our training for the past month to get ready for a dressage show, so we can go down the centerline straight. You're darn right about TB's and brains. He is one sharp cookie! Now before I teach him anything new, I ask myself what possible side effects it might produce.