Complex sentence: The rack or racking is a gait that is also known historically as the "Virginia Single-foot Gait," with many breeds of horses capable of producing this gait, but most commonly associated with the Five-Gaited American Saddlebred.
Split into simpler sentences: The rack or racking is a gait that is also known historically as the "Virginia Single-foot Gait," with many breeds of horses capable of producing this gait. It is most commonly associated with the Five-Gaited American Saddlebred.