I have learned a great method of teaching horses to round up, soften on the bit, soften to lateral flexion, round through the back, and keep wonderful impulsion. But, I am having a hard time figuring out how to explain how to do it. It definitely takes time and practice.
If anyone else knows what I am trying to explain, please jump in. It is important to start with bridle work from the ground. Bridle and saddle your horse as if you were going to ride, but stay on the ground. Have your reins over the neck as you would when you ride, and grab the rein on whatever side you decide to pick first. Hold the rein around a foot from the bit (varies depeding on size of horse), and sort of pull the rein forward with your hand; you are encouraging your horse to walk around you in a circle. Hold your hand at a height that encourages your horse to flex his neck and poll slightly toward you as well as lower his head to the height you dedire when riding in general. You will be looking for him to be holding his head at the lowered height, flexed inward, and near vertical to the ground, all while staying off the bit (not leaning on it or being pulled into position. To achieve this....when you ask your horse to lead out around you, if he doesn't immediately move forward to get away from the bit pressure add drive. This can be done in different ways depending on the natural energy of your horse. Escalate throught the steps so that you don't frighten or be unfair to your horse. 1. Ask to move by moving your hand in the direction 2. Kiss 3. Raise the free hand to show a dressage or other whip while making another kiss 4. Smack the dressage whip against your pant leg, boot, or ground to make a noise while making a kiss 5. Spank your horse lightly in the rear while making a kiss. Stop escalating whenever he responds by moving. If he leans on your hand while in the circle, add drive. If he continues to lean on your hand, disengage his hind quarters by quickly pulling his rein around to the fender area of the saddle and then immediately ask him to move forward again with drive. Do this 3 or 4 times in a row and until he stops leaning on you (I am not sure why this works, but it does). Continue adding drive or disengaging until your horse is walking/trotting in a small circle around you (you standing in place) with his head flexed in, down, and him flexed through the pole and neck, with no pressure or leaning on the bit. The point behind this lesson is more about learning self carriage and staying free by staying soft on the bit, and not using it and his riders hands as a steady.
When you get him great both sides from the ground, this exercise can be done from the saddle by doing serpentines. In the saddle, gently and softly pick up the rein, and if he doesn't immediately start moving his head in the direction you asked, moving his feet that way, and dropping his head so that there is no more contact on the bit, add some drive. Be sure to go through steps like above. As soon as he responds appropriately, give him huge slack, and let him move out freely on a loose rein as a reward. Do left turns, right turns, left circles, right circles, always asking him to bend his head, neck, and body to the appropriate amount for the turn. Learning to respond softly throughout the body on turns like this will begin to carry over in all of his movement, straight and turning. It is amazing how free and flowing his movement will begin to feel while stillhaving him be rounded, soft, supple, and responsive. The drive and softness to the bit are really the keys.
I warm up with 10-20 minutes of serpentines every time I ride, and I also go back and do the bridle work again periodically to make sure we are still communicating clearly. I have also found that the serpentines are an excellent focus exercise for when your horse gets distracted or worked up at a show or other event.
That is as clearly as I can explain it...there are many subtleties that I cannot explain in words...for that, you would want to work with a trainer who knows how to do this. (John Lyons style)