Satori Center

In The Natural Horse: Foundations for Natural Horsemanship by Jaime Jackson, I've come across several intriguing notions.

Here is one, p58:

Given the above, it comes as no surprise tha the muscles stretching across the back and abdomen of the wild and athletic horse are often well developed and conspicuous.  In fact, they are clear indicators that a horse is an athlete and has been moving naturally.  As Suenig wrote, "In well-trained horses, the cervical muscles [are] as hard as marble."  Xenophon comments, "A double-back is easier to sit upon and stronger."  (<they rode bareback>  The expression "double-back" refers to the cervical muscles Suenig describes that emerge along each side of the horse's spine.)  In horses that are "poor." or unathletic, these same muscles will fail to protrude, and the spine may rise above them.  Riding such horses may border on animal abuse.

What is your experience with this?