Exercise is great for a horse's health in so many ways. Just start slow, paying attention to how hard he's working, and build up slowly.
If you have horses that can do it, ponying is preferable to lunging, IMO, but not every horse or person can handle it. If you have a large enough pen, free lunging is an option. It can be done in a square pen, just takes training.
I can't imagine that regaining a healthy amount of weight would put undue stress on the legs if it didn't happen too fast. There also might be underlying issues causing stiffness. Might talk to the vet about that.
If the vet okays riding, start small and build up as with any conditioning program.
Posted via Mobile Device