Please see the following links for expert tips on training, biomechanics, saddle fitting, and more:

Exercises and Advice from Robert Dover

A Horseman's Approach to Eventing (William Fox-Pitt)

Creating Harmony and Expression

Build a Solid Foundation for Success with Mary King

The Healing Power of Dressage

Lessons for Dressage Instructors

The Physics of Flexion

How Stretching can Benefit your Horse

Correcting Rider Asymmetry

Saddle Fitting the Asymmetric Back

Six Veterinary Approved Tips on Saddle Fit

Dressage-Position 101 With Shannon Peters

Scott Hassler: Collection with Throughness and Forward Desire

The Importance of Riding in Stretching Position

Videos:

The following video provides excellent information on the mechanics of the horse's back.  Our special thanks to Equitopia for allowing us to share it. The research done at UC Davis Veterinary School is particularly significant.

Please see the The Physics of Flexion, and The Physics of Collection & the ESM  2012 abstract for more information on the subject (Related Articles link).