When should you ride with a slack rein?

Riding with a slack rein is neither universally correct nor universally wrong. It is a tool with specific appropriate applications, and understanding when it is the right tool requires understanding what the rein is communicating to the horse and what you are trying to develop or demonstrate at any given moment. The slack rein is most clearly appropriate as a reward. When a horse has responded correctly to a request — completed a transition softly, yielded to a leg aid, performed a maneuver correctly — releasing to a completely slack rein communicates in the clearest possible language that the right answer was found. This use of the slack rein as a release and reward is foundational to correct training regardless of discipline. A horse that never receives a complete release has no clear signal that he has done the right thing. The slack rein during warmup and cooldown is both physically and psychologically correct. At the beginning of a ride when muscles are cold, allowing the horse to walk on a long or completely loose rein for ten to fifteen minutes gives him time to warm his muscles through relaxed, natural movement and swing his back freely. The same principle applies at the end of work — cooling down on a loose rein allows the horse to stretch, lower his head, and decompress physically and mentally from the demands of the session. Western disciplines judged specifically on the horse's ability to perform on a loose or completely slack rein — reining, western pleasure, ranch riding, trail classes — require the slack rein as a demonstration of the horse's training level. A finished reining horse that performs sliding stops, spins, and lead changes on a completely slack rein is demonstrating that he has internalized his training so thoroughly that he no longer needs rein guidance to perform correctly. The slack rein is specifically not appropriate when the horse is green and has not developed the self-carriage that would allow him to maintain correct work without rein guidance. The distinction that clarifies all of this is the difference between a horse that goes on a slack rein because he is trained to maintain his way of going independently, and a horse that goes on a slack rein because the rider has given up the conversation. The first is a demonstration of advanced horsemanship. The second is an abdication of responsibility.