What can I do with ground work to improve hindquarter use?

Groundwork for developing hindquarter engagement is one of the most underutilized tools in horsemanship, and it is particularly valuable because it allows you to develop the horse's physical awareness, strength, and responsiveness to lateral pressure without the added complexity of carrying a rider — which means the horse can focus entirely on learning to use his body correctly before the weight and balance demands of a rider are added. Yielding the hindquarters is the foundational exercise and the starting point. Stand at the horse's shoulder, apply pressure on the horse's hip or flank, and ask him to step his inside hind leg across and in front of his outside hind — stepping away from the pressure in a crossing motion. The crossing motion is the key detail. Build from one crossing step to a full half-circle around the front feet and eventually a full circle in both directions until the response is light, immediate, and soft equally in both directions. Longeing with intention is one of the most powerful hindquarter development tools available, and the difference between productive and unproductive longeing is almost entirely about what you are asking the horse to do with his hind end. Encourage the reaching hind leg by working transitions on the longe — walk to trot, trot to walk — with frequent transitions that ask the hindquarters to engage and carry. Downward transitions on the longe are particularly valuable because they require the horse to shift weight rearward and step under with the hind legs to balance the deceleration. Spiral circles — progressively decreasing and then increasing the longe circle — develop both hindquarter engagement and lateral suppleness simultaneously. As the circle decreases the horse must step further under himself to maintain balance. As the circle increases the horse learns to push from behind and extend the stride. Cavalletti and ground poles placed on a circle or straight line encourage the horse to step more actively with his hind legs without specific training pressure. Hill work done in hand or on the longe is the most powerful tool for raw hindquarter strength — walking and trotting uphill requires the hindquarters to push the horse's entire body weight up the incline, developing the gluteal, hamstring, and stifle muscles that power engagement and collection.