Maybe not natural... but watch some CIC**** eventing XC video sometime, and you decide if you think horses would do that if they didn't like it. I ended up in the snow today (landed on my feet, buffs nails... :) ) when my horse had some strong opinions about not being allowed to go faster than a walk around our XC course...

Same with other jumping sports... you can't really sore or scare a horse into doing it... at least not well...