If the horse inverts in transitions, there are several possible causes. Some of them have to do with the horse, some of them have more to do with the rider.
Transitions are always susceptible to mistakes because the footfall and the balance have to change.
Typical Horse Mistakes
Higher gaits require a higher energy level and core muscle engagement than lower gaits. Otherwise, the horse won’t be able to transition from walk to trot or canter.
If the outside hind leg doesn’t flex enough under the body mass, the horse won’t be able to lift his forehand into the canter.
For down transitions, the hind legs need to flex and allow the half halts to go through.
A good up transition also means that the hind legs have to “squat and lift” the body mass up, and a good down transition means that the hind legs have to sit and support the body mass. This is harder work than just “cruising” in the same gait. Since both hind legs are not equally strong or supple, many horses have a tendency to get crooked in transitions, and when they get crooked, they invert or curl up, depending on their specific conformation.
The correction is therefore clear: work on improving the horse’s balance, alignment and straightness, as well as his suppleness and permeability. Then the transitions will improve as a result.
Typical Rider Mistakes
The rider is the other very likely source of the problem.
If the timing of the aids is poor, the horse is unable to execute what the rider is asking of him because the seat and aids are working against the laws of physics instead of with them.
In up transitions, riders often grip or squeeze with their legs so that the horse holds his breath and braces with his rib cage against the leg.
Gripping legs often lead to locked hips, which blocks the horse’s hips.
Some riders push the horse forward with their seat bones, so that the horse drops his back, inverts, and falls onto the forehand.
If the reins are too short or too long, the horse will not be able to perform a good up or down transition.
In down transitions, many riders pull on the reins so that the horse’s back drops and the hind legs are pushed out behind.
Some riders don’t have a good enough connection between their pelvis and elbow, so that the horse doesn’t understand the half halt and therefore resists against it.
Half halting on both reins instead of only one often provokes resistance from the horse.
Sitting too heavily will drop the horse’s back and prevent the hind legs from engaging.
If you and your horse have trouble producing good transitions, check your seat and aids. Make sure you apply your aids during the proper window in the footfall sequence. Stay connected between your pelvis and elbows. Keep your leg and arm muscles relaxed so that your hips, knees ankles, shoulders, elbows, wrists, and fingers can move freely. Don’t forget the release, even if an aid didn’t go through. In that case, prepare the horse and ask again with modified aids and better timing.
