How can the rider gain control over the hind legs? That depends on the horse and rider. Main considerations are the straightness as well as the ratio of thrust to carriage of the hind legs, in other words: balance.
Most horses are naturally unbalanced in this respect when they begin their (re-)training under saddle. They either thrust more than they carry or, less frequently, they carry more than they thrust. Conformation plays an important role, and so does any prior training. E.g. horses who have very straight hind legs tend to thrust more than they carry. Horses whose hind legs are built out behind themselves will also thrust more. On the other hand, sickle hocked horses carry more than they thrust, due to the angles of their hind leg joints. The Old Masters used to say these horses overburden their hindquarters. Additionally, as long as the horse is not completely straight, one hind leg thrusts more than the other.
The practical repercussion of excessive thrust is either a very heavy rein contact or an inverted horse (sometimes both). A horse who lacks thrust, on the other hand, will not approach the bit. He will consequently feel light, but he will be sucked back. In other words, he offers a false lightness that the rider must not accept. When both thrust and carriage are equal, the horse feels honestly light.
The rider’s job is to evaluate the horse in these terms and to custom design a training program that is aimed at balancing out the thrust and the carrying power in each hind leg as well as the activity level of both hind legs in comparison to each other. We should proceed by trying to increase the defective pole of the opposition, rather than diminishing the excessive one. In practical terms, this means that a horse who does not thrust enough must be ridden forward on straight lines in a fresh, big working trot. Tight turns must be avoided at that stage, as they would only invite him to suck back even more at this point. Horses like this frequently offer the canter, as their natural crookedness leads to the hind leg on the stiff side thrusting more. The hind leg on the hollow side consequently takes a longer stride, but does not stay on the ground long enough for the opposite (stiff) hind leg to reach forward. The stride consequently becomes asymmetrical, and the canter develops. When this happens, the rider rides the horse forward at the canter for a long side and then brings him back to the trot. As soon as the rider feels the transition come through, he “changes gears” and sends the horse forward again in a big trot. Care must be taken that the trot is big, not fast.
If a horse thrusts without carrying, free gaits must be avoided temporarily. Instead, he needs to be worked on circles, voltes, spirals, serpentines, and eventually in lateral movements. These horses benefit a great deal from bending exercises at the walk. The stride length at the trot and canter has to remain more moderate, thinking of collection rather than extension. If a horse like that were ridden forward on straight lines, the gulf between thrust and carriage would become even larger. The horse would become heavier and more unbalanced.
As soon as the initial imbalance of forces is evened out and about to switch, the rider has to reverse his strategy. In other words, the initially sucked back horse will start to thrust more than he carries, at which point he has to be worked in bending exercises, more moderate gaits, towards collection. The initially heavy horse will reach a point where he needs to go forward in free gaits, such as lengthenings at the trot and the canter, in order to avoid a loss of impulsion and prevent him from sucking back.
An important factor in this discussion is the vector of the thrust, i.e. the direction in which the horse exercises his thrust. Initially, this vector will have a horizontal, forward direction. In bad cases, the force seems to act in a forward-downward direction, which makes you feel as if you were riding down a slope, even when you are on perfectly level ground. The rider now has to raise the trajectory of the thrusting forces, which allows him to maintain the thrust undiminished but to increase the horse’s carrying ability. This actually makes it necessary to animate the hind legs more first, so that they reach more forward. Increasing the angle of the trajectory of their force causes the horse to lift the airborne hind leg higher. It is made possible by tucking the pelvis and flexing all the joints of the hind legs.
Another aspect of this type of balance is that thrust and carriage may match at 5%, 20%, 50% etc. of the horse’s physical ability. Inexperienced riders are often content with their horse working at a fraction of their capacity, because the horse feels light and pleasant, not realizing how much the horse is actually holding back. Our goal is to teach the horse right from the start to use all of his strength in a productive way during his work, without holding anything back. It has to become a habit for the horse to work close to 100% capacity all the time. This is a goal, an ideal. It may not be entirely realistic to expect to reach full capacity all the time, but we should try to get as close as possible every day. Of course, the absolute value of the thrusting and carrying forces will increase over time. The 100% energy output of a green horse is significantly smaller than the 100% output of a Grand Prix horse.
Every time we have evened out the thrusting and carrying forces at a certain level of capacity and we want to raise the general level of activity, we have to start by increasing the thrust first, which brings the hind legs closer to the center of gravity and leads to a greater articulation of the joints – if, and only if, the trajectory of the thrust is forward-upward. Any new demand requires a greater effort on the horse’s part, whether it is a corner, a volte, a transition, a change of bend, a movement, or a request for a higher quality of the basic gait. It is harder work for the haunches than just cruising along. If we fail to animate especially the inside hind leg more first, the following demand will be executed poorly (or fail altogether). This cannot be emphasized enough, because it is of such tremendous importance. Yet, you see riders forgetting it all the time. The temporal delay between increasing the thrust and asking for more carriage (in essence more collection) can be as short as a split second, but it has to be there. First ask the hind leg to step under, then ask the horse to sit down on it.
Increasing the thrust will result in a temporary increase in rein contact, because the horse steps into the rider’s hand with greater determination. As long as the rein aids still go through and the horse is not just leaning on the bit, that is acceptable. The rein contact will become lighter again as soon as the flexion of the haunches has increased also and matches the thrust again.
READ MORE ABOUT AUTHOR: DR. THOMAS RITTER