I ride a 6 year old Mustang jumper-pony. I've been working with him for the past 2 years, and we are working on more advanced stuff now. He is stubborn to move his back end, and to move off my leg. But the other day during my flat lesson my trainer noticed something new. She told me to give him more rein when we were working on our transitions, then when I was walking him out he kept stretching towards the ground. He has always wanted to stretch out, but we are wondering I he might be sore. The vet thinks that his problem is that his conformation is a small base, but I am wondering if something else is bothering him. If you have any ideas let me know! Thanks a ton!