What are martingales, when are they used, and how do they work?

Martingales are training and management aids that limit how high a horse can carry its head, preventing it from evading bit contact by throwing its head above the point of rein effectiveness. They are used in various English and western disciplines as supplemental equipment for horses that habitually carry their heads too high, toss their heads to avoid contact, or for safety reasons in jumping where a horse flipping its head at the wrong moment can strike the rider. A running martingale attaches to the girth at one end and splits into two rings through which the reins pass at the other. When the horse's head rises above the point where the rings create a straight line from the bit to the rider's hand, the martingale begins to apply downward pressure on the bit through the reins. Below that point, the running martingale is inactive and allows the rein to act directly without interference. This intermittent action makes the running martingale a relatively mild and widely used piece of equipment. A standing martingale attaches to the girth at one end and to the noseband at the other, creating a fixed restriction on how high the horse can raise its head. It does not influence the rein or the bit but simply provides a physical stop for extreme head elevation. Neither type of martingale produces the correct head carriage that classical training develops from behind — they address the symptom of high head carriage without developing the hindquarter engagement and back suppleness that correct head carriage requires. Used appropriately alongside correct training, they provide a management tool; used as a substitute for training, they maintain a training problem rather than resolving it.