(please post a picture of your 'writing assistant')
Many training programs are just traditional for that particular style of riding, but there is some science now that backs up a lot of traditional practices(and does not back up others, cackle). Some of the research is from racing and doesn't actually translate well to other riding sports, but some is very useful.
What good trainers do to fitten up dressage horses is just incredible. The horses get ridden several times a day, do hills, go on a treadmill, on a Eurociser, grazed on a lead, hand walked, they are so fit you break your hand on the muscle if you pat 'em, LOL.