Using yielding exercises to soften a stiff or resistant horse is one of the most reliable approaches in horsemanship because it addresses stiffness at its root — a failure to yield — rather than trying to force softness through increased pressure, which almost always produces more stiffness rather than less. The key insight is that suppleness and softness are the result of yielding, not the prerequisite for it, and that consistent, patient yielding exercises build both physical flexibility and mental willingness over time.
For a physically stiff horse — one that is tight through the neck, back, and hips — lateral flexion exercises done consistently on both sides develop the neck and shoulder suppleness that all other softness depends on. Asking the horse to bend its neck toward the rider's boot from the saddle, or toward the handler from the ground, and holding the light contact until the horse softens through the poll and jaw and releases the tension, is a direct and effective approach to physical stiffness. The horse cannot be forced supple — it can only be invited to yield, and the yielding produces the suppleness.
For a mentally resistant horse — one that stiffens in response to any request rather than as a result of physical limitation — the approach must address the emotional state underlying the resistance before the physical exercises will be effective. A horse that is stiff because it is anxious, confused, or in a defensive posture toward the handler needs lower-intensity work in safer environments before any specific suppleness exercise will be productive. Warwick Schiller's emphasis on building the horse's trust and security before demanding specific physical responses is directly applicable here.
The progression for softening a resistant horse through yielding typically moves from large, easy-to-produce movements to progressively smaller and finer ones — from full body direction changes to half-steps of lateral flexion to the subtlest softening through the jaw and poll. Each stage of refinement builds on the previous one, and each represents a deepening of the horse's understanding that yielding is safe, productive, and reliably produces relief.