Just wanted to point out that strong muscles do NOT mean strong tendons and bones. Muscles strengthen much, much faster than any other part of the body. That’s why you see so many tendon/ligament issues. The horse looks like he can handle it because his muscles are huge, but the rest of him isn’t caught up yet. It’s important to keep in mind that, especially in young horses, the rest of the horse may not be as fit as he looks.
I agree with part, but not all of this.
It is my understanding that many (if not most) ligament and tendon injuries happen when the MUSCLES get tired and weak, and the tendons/ligaments end up taking over more of the burden.
(That is why “riding in deep mud” results in tendon injuries - because the muscles tire much faster in mud)
What counts is the ENDURANCE of the muscles, not their bulk.
That is why you start with LSD to build up the strength of the ligaments and tendons, then you do “power” work to build up the strength of the muscles, and then you do “conditioning” work to build the muscle endurance, and to build up wind and heart. How much you need depends on the discipline and the level. But until you have all of it in balance, you don’t truly have a “fit” horse.