How to strengthen cuffs on dogs

What is the best way to strengthen the tendons of a young horse? (soft shackles)

Hello,

I am currently working from the ground with my 3-year-old Arab mare (lunging, guiding in the terrain, Liberty etc.). She is used to working with the bridle, and now also to working with the saddle. Remain calm when saddling up, and know it when walking (step, trot) (FOR A SHORT TIME and I'm NEVER talking about more than 20s at a time!) To have some weight (approx. Fortunately, it is extremely related to me.

With the general riding, I definitely want to take my time until next spring or even summer, in my opinion it is at least a bit far behind.

But I wonder if I could start next year with it for a short time, as I said 20s, to rely on them. No riding, just getting used to sitting up slowly .. Hopefully it is clear that I don't just throw myself on it, I know that I own a sensitive young horse and not an old loop pony! I give her all the time she needs to develop, and don't worry, as a yearling she never had to carry weight or anything like that!

Thanks for your help in advance!

LG