What makes a good reining lead change?

A good reining lead change is clean, straight, smooth, and on cue — and all four of those qualities must be present simultaneously for the change to score well in competition. Clean means both the front and hind lead change in the same stride rather than the horse changing in front first and catching up behind a stride later, which is a late change and results in a score deduction. Straight means the horse travels a straight line through the change rather than drifting left or right, jumping sideways, or swinging its hindquarters out of alignment at the moment of the change. Straightness through the change is both a training indicator and a physical requirement: a horse that drifts during the change is not balanced and aligned correctly through its body, and the change reflects that lack of alignment. Smooth means the change happens without a visible jump in the horse's movement, without speeding up through the transition, and without the horse bracing or becoming tense at the moment of the change. A horse that jumps or surges through the change is reacting to the cue rather than responding to it, which indicates the change has not been built to a confident, relaxed depth. On cue means the change happens when the rider asks for it — not before based on the horse's anticipation of the location, and not a stride after because the horse is slow to respond. The combination of clean, straight, smooth, and on cue is only possible in a horse whose foundational body control — straightness, hip movement, shoulder control, and balance — is confirmed well enough that the change can be performed without physical or mental disruption to the horse's way of going.