How do you develop a young horse's suppleness and straightness from the earliest stages of training?

Suppleness and straightness are foundational qualities that become progressively more difficult to develop if neglected early, and both Clinton Anderson and Pat Parelli teach addressing them from the beginning of training rather than treating them as refinements for later. Suppleness — the horse's ability to bend laterally through its body without stiffness or resistance — is developed first on the ground through the same yielding exercises that teach the horse to move away from pressure. A horse that yields its hindquarters softly, yields its forequarters, and bends its neck laterally to halter pressure is developing suppleness before it is ever ridden. When the horse is started under saddle, this existing suppleness translates directly into responsiveness to lateral rein and leg aids. Parelli's approach develops suppleness through the Seven Games, particularly the Porcupine Game and the Sideways Game. A horse that is fluid and willing through these games has developed the lateral flexibility in its neck, barrel, and hindquarters that make it a pleasant horse to ride — one that follows a rein without stiffness and bends around a corner without bracing. Straightness — the horse traveling with its hind feet tracking in the same path as its front feet — is harder to address in young horses because most horses are naturally slightly one-sided. Anderson develops straightness by being deliberate about working both directions equally and by not allowing the young horse to drift, cut corners, or travel with its hindquarters offset without correction. The early habit of traveling straight is much easier to establish than correcting established crookedness later. Warwick Schiller notes that a horse's natural crookedness is often an expression of an underlying asymmetry in muscle development or joint flexibility, and that simply correcting the straightness without addressing the underlying asymmetry produces temporary straightness at best. He recommends being attentive to which direction the horse bends more easily and specifically developing the stiffer direction with additional suppling work.