Wondering if any of you have advice on exercises to build muscle in a horse? I have a roundpen and he lunges on both a line and free in the pen. The pen is a little small, which poses a bit of a problem and limits some things I can do. Looking to get his rump and topline a little more defined. Considering building an obstacle course - just looking to mix it up a bit and do something new. What we've been doing has been slow at showing results and I'm sure bores the heck out my horse.