I know there is a post down below similar, so sorry :(
The two new guys are lacking muscle, and before we start riding heavily, not only are we getting their weight up, but also want to build muscle. They need topline, rear/rump, and stifle muscle work.
I read to have them go over ground poles and cavaleties will help their toplines, and we're doing this. (Now, just started yesterday, so I know its to soon to tell.) We're also using a tie-down system my friend uses on her TB/Paint to keep his topline up and strong. We also do a large amount of stops and turns, unfortuantly, Levi isn't found of turning, and won't turn unless I turn him. Hondo will turn, though. I also alternate tacked and untacked. But no weight yet, on Levi, because his muscles are the worst. Hondos are in better shape, so husband has ridden him once.
What is there to do to help with rear end/stifle areas? Is there anything else that I can do more?