I have a 4 yo Mustang gelding that I purchased about 3 mo ago. He was pulling on me quite a bit and fussy with his bit, tossing his head, trying to chew on reins, etc. I finally found a bit he likes and we've been working and he's doing great. However when he gets cranky and wants to do other things besides what I'm asking he pulls on me. We've been doing lost of flexing with his head/neck, yielding hindquarters and even some forequarters on the ground. I also understand that I need to soften his ribcage in order for him to get soft/supple and that will in turn resolve the pulling on me. My question though is what exercises are effective for bending/softening the ribcage?