Jimbo-- evolution isn\'t really accurate. If it were only that, the species (both human and equine) would evolve in a lot of ways, and the bones, tendons etc. would evolve along with the muscles. But what is happening is that market forces are driving the advances in just one area (ability, or speed), while ignoring soundness. Weight training, supplements, etc are generally designed to just increase muscle mass (and other performance aspects) in humans, and the equivalents in horses. When you get muscles too strong for the support system you get (from my era) Koufax and Mantle. And really fast, unsound horses.
My own opinion, and it comes in part from dealing with a lot of horses and top trainers over the years, is that many injuries are caused by the stress of running too fast, but it\'s not always a simple, direct cause and effect. Sometimes a big effort can cause a horse to feel pain (minor injury, muscle soreness etc.) and alter his stride in subsequent works or races. Given the huge amounts of weight loads landing on small areas and the complex mechanics of the racehorse, a slight change can have disastrous effects-- the same thing happens when pitchers alter their deliveries because of an injury.
One of the things Jon Forbes told me is when you find an injury, look elswhere to see if it happened because the horse was trying to \"get off\" (not put weight) somewhere else. That guy is a very good trainer, by the way-- one of the very best, if not the best, horsemen I ever dealt with. The Maryland guys in general are really good pure horsemen.
