Most Thoroughbreds come off the track knowing how to do a lead change, having learned that skill in race training. But they are used to doing flying changes at speed on a large and wide track. When the horses start riding in a much smaller arena, they may become claustrophobic, and they likely don't have the muscles needed to perform a clean, balanced change in a smaller space and at a slower speed. To help your OTTB with his transitions and changes, try this exercise, demonstrated by MMSC Trainer Kara Toye on Photo Shoot. Canter big circles with changes of direction and simple changes, making sure your horse is balanced in the turns, not rushing, and not anticipating a flying change. As he builds up strength, the balance will come more naturally, and pretty soon your simple change will be an uphill, balanced flying change.
Learn more about Photo Shoot here: www.secretariatcenter.org/horses/photo-shoot