Introduction
When riding lateral movements many riders follow the FEI rule book that defines specific angles for the shoulder-in, haunches-in, or half pass. There are often heated debates about whether lateral movements should be performed on 3 tracks or on 4 tracks. These riders are discussing the finished product without considering the road that leads to it. And they are not thinking about the gymnastic considerations that play a role in this.
Lateral Bend
All true lateral movements are ridden with a lateral bend (the leg yield is not ridden with a lateral bend, which is why it is not a true lateral movement in the classical sense of the word). The lateral bend allows the horse to step underneath the center of gravity with both hind legs while he is moving forward and sideways. That is to say, it enables him to stay functionally straight. If the horse doesn’t bend, one hind leg will step away from the center of gravity (i.e. the horse gets crooked). In the shoulder-in it’s the outside hind leg. In the haunches-in, renvers, and half pass it’s the inside hind leg that will move next to the body, rather than stepping underneath it.
The lateral bend always corresponds to a circle of a certain size. This is the reason why the Spanish Riding School in Vienna used to ride a volte in the first corner of the long side to create the necessary bend before starting a shoulder-in or a half pass.
If you picture your horse being aligned on a circle line, with the left pair of legs on the left side of the line, the right pair of legs on the right side of the line, and the spine forming a segment of the line, you can see that the lateral bend has to increase as the size of the circle diminishes.
The smaller the circle, the more the horse has to bend, and the more the inside hind leg has to support the body mass and flex its joints. In other words, there is a correlation between bend and collection as well as circle size and collection. More bend requires a higher degree of collection, and a tighter turn requires a higher degree of collection as well.
Bend and Angle
How does this relate to lateral movements? In each lateral movement one leg of the horse is placed on the line of travel, while the opposite end of the horse is moved away from the line.
In the shoulder-in, the outside hind leg is on the 1st track, while the front legs are moved to the inside.
In the haunches-in, the outside front leg is on the 1st track, while the hind legs are moved to the inside.
In the counter shoulder-in, the inside front leg is on the 1st track, while the hind legs are moved to the inside.
In the renvers, the inside hind leg is on the 1st track, while the front legs are moved to the inside.
In the half pass, the outside front leg is on the diagonal, while the hind legs are moved to the inside, just like in a haunches-in. That’s why some trainers say that a half pass is essentially a haunches-in on the diagonal.
Alternatively, you could think of the half pass as a renvers on a diagonal. Some classical authors view the half pass as a renvers because the horse arrives on the opposite long side in a renvers position. In that case, the inside hind leg would be on the diagonal, while the front legs are moved towards the outside of the bend.
Bend, Angle, and Collection
If you visualise a horse in a shoulder-in on the long side, you can draw a circle in your mind that corresponds to the lateral bend of the horse, so that his feet and his spine would be aligned on this circle line.
You can visualise the horse either from above or from directly in front or behind. Depending on the moment of the footfall sequence in which a still photo is taken you may not even be able to tell from the picture whether the horse is in a shoulder-in or whether he is shown in the first step of a circle because the outside hind leg is on the long side and the shoulders have already turned towards the inside.
If the horse is aligned on a 20m circle, the bend is relatively shallow, and his front legs are relatively close to the 1st track. This will be more of a shoulder-fore.
If the horse is aligned on a 10m volte, the bend is more intense and the forehand will be farther away from the 1st track. If you are looking from the front or from behind you can probably see 3 legs.
If the horse is aligned on a 6m volte, the bend is even more intense, and the forehand will be much farther away from the 1st track. If you are looking from the front or from behind you can probably see 4 legs.
Similarly, the haunches-in corresponds to the last step of a volte. The outside front leg is already on the long side and the haunches are still on the volte. When the bend corresponds to a 20m circle, the haunches may only be a hoof breadth to the inside of the front legs. When the bend corresponds to a 6m volte, the horse is moving on 4 tracks.
Practical Repercussions
This has serious practical repercussions for the training of the horse. We had seen above that there is an inverse relationship between the turn radius and the degree of collection: the smaller the turn radius, the higher the degree of collection needs to be because the inside hind leg has to support a larger share of the weight in a pirouette than on a 20m circle. We had also seen that the turn radius has a direct correlation with the lateral bend: The tighter the turn, the more intense the bend needs to be. This means that in order be able to bend more, the horse has to collect more. Collection (i.e. flexion of the haunches) requires flexibility and strength in the hindquarters, which is why we don’t ride small voltes or canter pirouettes with green horses. Due to their lack of strength and flexibility, It would break down their hocks and damage their tendons.
And since the degree of the angle in lateral movements is directly tied to the bend and the radius of a specific circle, a steeper angle corresponds to a smaller circle with a more intense bend and a higher degree of collection.
Homeopathic Doses
In competitions, the angle of the lateral movements is fixed, which means that the horse has to have reached a certain level of training before he is able to perform them with the required angle, bend, and degree of collection.
However, you don’t need to wait that long to take advantage of the gymnastic benefits of lateral movements if you modify them by reducing the angle between the horse’s body and the line of travel. A shallower angle means that the corresponding circle is larger, the horse has to bend less, and he has to collect less.
This is where the idea of “homeopathic doses” comes in. If you don’t think of lateral movements in rigid terms, i.e. that they absolutely have to have a specific angle, like 33 degrees or 45 degrees, but if you think of them, rather, as being on a continuum between 0 degrees and 45 degrees, you have a lot more flexibility. This means that you can start to introduce the concept of lateral movements much earlier in training without hurting the horse.
You can move the shoulders or the hindquarters sideways by one hoof breadth or half a hoof breadth so that the angle of the horse’s body is perhaps 10 degrees or only 5 degrees and the corresponding circle would have a diameter of 20m or even more.
When you are introducing half passes you can make the diagonal line shallower, e.g. from A/C to the end of the long side, so that the horse moves 10m sideways for a length of 40m or 60m. Or you start at the beginning of the long side and ride only to the first quarter line, so that the horse moves 5m sideways and 40m or 60m straight.
When you adjust the angle, you're not riding a full-fledged shoulder-in, haunches-in, or half pass. But you get all the gymnastic benefits without any negative side effects. It also helps to ride these movements only for a few strides, and then turn onto a volte or return to a single track.
Conclusion
Lateral movements in homeopathic doses are great straightening and suppling exercises, even for less advanced horses. They are gentle, yet very effective. In some ways, lateral movements with shallow angles are actually more difficult to ride because they show you immediately if or where the horse tries to evade.
Some horses like to go very steeply sideways. They are typically short-backed, with a very round rib cage. Bending doesn’t come easily to them, so they compensate by swinging their haunches sideways. This makes them crooked. One hind leg steps away from the body mass, and the rib cage can stay straight, without bending or rotating. They benefit from riding lateral movements in homeopathic doses in order to develop their lateral bend and to become more supple in their spine and hindquarters. Combinations of lateral movements are often especially useful because you can engage one hind leg after the other for a few strides each. When you add voltes or corners, you bring the outside shoulder closer to the inside hind leg. This shortens the main diagonal, which helps the horse to lift his back. Due to the natural crookedness, the hind leg on the hollow/concave side and the front leg on the stiff/convex side tend to repel each other like magnets of the same polarity. This leads to a lack of balance and engagement. The closer these two legs can be brought together, the straighter, more balanced, and rounder the horse will become.
