Explain what spiral in and spiral out is?

Spiral in and spiral out are the two distinct phases of the spiraling circle exercise, and while they are part of the same continuous movement they produce different gymnastic effects on the horse's body and develop different qualities — understanding each phase separately gives the rider a clearer picture of what she is actually developing and why each direction of the spiral matters equally rather than one being simply the return trip from the other. Spiral in is the collecting, compressing, carrying phase where the working circle is progressively decreased in size. As the circle tightens the horse must engage his hindquarters more deeply to balance on the shrinking arc, bend more through his ribcage to follow the tighter curve, and shorten and elevate his stride to navigate the smaller path without losing rhythm or balance. The inside leg is the primary aid — maintaining bend and forward energy while allowing the outside rein to contain the arc and bring the circle gradually inward. The outside leg guards the hindquarters from swinging out and ensures the horse bends through his whole body rather than just tipping his nose in. The quality of the inward spiral is determined by whether the horse maintains correctness throughout the decreasing size. A horse that spirals from twenty meters to fifteen in correct bend, consistent rhythm, and genuine inside hind engagement has executed the exercise correctly at his current level. A horse forced smaller than his physical capacity can support deteriorates through the exercise rather than developing through it — the minimum size is always defined by where quality ends, not by any fixed diameter goal. Spiral out is the pushing, releasing, extending phase where the circle expands back from the minimum size toward the original working diameter. The horse is asked to push from the hindquarters and lengthen his stride to cover the larger arc — the energy compressed into collection through the inward phase is released forward and outward. A horse correctly spiraled in will step out onto the larger circle with noticeably more swing, reach, and impulsion than he carried before the spiral began. The outside leg drives the hindquarters out onto the larger circle, the inside rein softens and allows the horse to lengthen through his neck, and the rider's seat opens and follows rather than containing. The connection between the two phases is what makes the exercise more than the sum of its parts. Together, the contrast between compression inward and release outward teaches the horse to be elastic in his stride length and his degree of collection — to compress when asked and release when allowed without losing rhythm, balance, or forward energy through either transition. That elasticity is one of the defining qualities of a truly supple well-trained horse, and the spiral exercise develops it in a context that is continuous, progressive, and immediately self-correcting.