I always thought that competing in equestrian sports was something that someone could not begin after a certain age -- that it was best learned when one was a child or teenager. I am also under the impression that Reeve did not take up competitive equestrian sports until his late 20s or early 30s. If some one takes up these sports when they are very young, one's instincts would be more in tune with the horse and avoid the kind of accident that paralyzed Reeve. Is this a correct judgement? I for one -- well past the age of 30 -- would not take up equestrian contests or horse races of any time. Horse back riding would be quite another thing.
You are absolutely right. I think of riding like gymnastics. An adult just learning wouldn't go to Bela Karolyi to learn the uneven bars, they would stick with something easy. Why would someone who had only been riding a couple of years do something as risky as cross country jumping? Over-confidence would be a major factor. There is something about the horse industry that makes people feel like experts with only a few years experience.
It sounds plausible, but an additional factor--one I seem to recall reading about at some point in the last nine years--was Reeve's size. He was a tall guy, and powerfully built (I mean, after all--he was Superman!) and the momentum, if that's the term I want, his body had as it was thrown down was enough to break his neck. What I mean is, and what I read explicitly said, that a smaller man (or a woman) might have been able to literally walk away from that accident.