Oh, you mean Classical Equitation!!!
I rather suspected that was the case. Sadly, much of the equitation practiced in the "gaited" community is just bad riding. Combine this with a real lack of understanding of equine biomechanics and you've got a recipe for horses in constant pain.
One of the best "how to" books out there is Vol. I (Education of the Rider
) of the Horsemanship and Horsemastership series. This was the textbook used at the U.S. Cavalry School at Ft. Riley from 1935 to the end of the Horse Cavalry in 1948. It is very well written and, when combined with Vol II (Education of the Horse
) you have all the written material you need to effectively ride and train any horse (gaited or trotter). Purchase them from the Suttler's Store at the U.S. Cavalry Association website, U.S.Cavalry Association: Fort Riley, KS
Hit "Shop" and the book is on the second row of "featured products." It will cost you $13.95 plus shipping. If you want to get the rest of the story
, purchase the three DVDs that were used to train troopers in those days.
If you really want to go deep in this then get Give Your Horse A Chance
by Lt. Col. A.L. D'Endrody. The author was the Chief of Cavalry Instruction for Hungarian Army in the 1930s. Silver Medalist at Berlin in 1936, IIRC. He didn't teach students; he taught instructors to teach students. This book is not light reading but it has more content than any equestrian text book I've ever seen.
These, plus good ground coaching, will allow you go get maximum performance from your horse no matter the gait (lateral, centered, or diagonal).