The FEI definition of rhythm is as follows:
Rhythm – The Regularity and Tempo
The first step of the training scale that should be established is the rhythm. The regularity is the correct sequence of the footfall, and the tempo is the speed of the rhythm. The rhythm is the regularity of the beat in all paces. Steps and strides in each variation of the pace should cover equal distances and also be of equal duration remaining in a consistent tempo. The rhythm should also be maintained through the transitions within a pace and in all turns, also in the corners, as well as on straight lines. No exercise can be good if the horse is losing rhythm. A loss of rhythm is often a sign of incorrect training. In order to judge the correctness of the rhythm, the judge must know how the horse moves in the basic paces.
As you can see, it’s a very good but quite lengthy explanation for one word. The last sentence referring to a knowledge of the basic paces is important.
To have a good understanding of rhythm/takt in training, we must consider the following: tempo, the length of stride, and the speed the horse travels. These three variables are very important training tools for every dressage rider. They are tools we can use because we have the power to influence them. We must be aware of them. One example of how to think about this might be a horse that is “running”. In this instance, the tempo is too quick, the length of stride unchanged, and the speed of the horse is too fast.
An experienced trainer will have a very acute awareness of rhythm/takt. They are able to help the horse to find its “sweet spot” and organise the variables with precision. To a good trainer, finding a horse’s natural rhythm/takt is second nature.
It’s important to remember at this stage that takt is a naturally occurring trait; the purity of the pace and the rhythm and regularity of the horse is something it poses naturally to a greater or lesser degree.
It’s something the horse already has and as such, with good riding, it can be maintained and developed. On the other hand, if mistakes are made, it’s something we can also lose. In this way, a loss of rhythm can indicate problems in the training. Although we may try to isolate rhythm as an element, the truth is it doesn’t exist totally on its own. Even in a young horse, all the other elements of the Training Program are present, but not in an established or consistent way.