Pilates for the Dressage Rider, by Janice Dulak.
No need for specialized equipment with Pilates! A ground mat would make these exercises a little more comfortable, however. "Pilates is a body conditioning method that is safe and effective for all ages and body types" that begins with core strength. Most exercises, illustrated with b&w photos, are low impact and non-weightbearing. After several chapters of matwork, it's on to mounted Pilates with some basic positions, then some applications specific to dressage.
Hardcover, 158 pages