Observation
It corresponds to the suite and the end of the dorsal spine from the 9th to the 18th vertebra and to the lumbar spine to the sacroiliac joint which locates at the tip of the rump.
This part of the spine is covered by the back-strap muscle which plays an essential role in the curvature, elevation and lowering of the back.
The back is judged in its orientation, its length and its width, the horse being stationary, in balance with a neckline in a natural position. The shape of the back is the line that goes from the insertion of the sacrum (tip of the rump) at the base of the withers.
Its width is assessed by looking at the horse from the front and from behind.

 

Characterization
The length of the segment that goes from the sacrum to the withers, or its inclination, which were assessed in the silhouette will not be measured, but its curvature and width. The curvature of this segment will determine if the back is "straight" or "hollow"
This evaluation is done visually, it must take into account the age of the horse and its state of work. Aging and loosing muscles, the back is hollow, but during growth, it can also adopt a hollow shape which will lessen in adulthood.

 

Meaning
The back provides the link between the front and the hindquarters and it supports the weight of the rider.
As the boom of the jumper, it will determine the power of the jump and the shape of the path.
As the boom of the jumper, if it is too flexible, it loses power and if it's too stiff, it requires too much effort for the rest of the body to fold. The width of the back contributes to its power but antagonizes its flexibility. If it's too hollow, it will be more difficult to raise and fold to get a good vertical propulsion, but it will facilitate the amplitude of the stride. If it's too rigid and straight, it will be difficult to fold.
The upper line training is an essential element of the role of the rider to prepare to be successful. Sharing with the rider his feeling about the flexibility, strength and the natural mobility of the back is an important element for the breeder to assess this aspect of the natural predisposition of a mare to produce a jumper.

 

 

Discussion
It's a matter of choice: A good balance between flexibility, power and scope is a must. It's also a matter of temperament at work and the horse's ability to accept and remember with the back in place.
A slightly downhill back, if it is wide and flexible, is compatible with the high-level performance, but more difficult to work properly. A somewhat rigid and straight back is easier to use in the right direction, but it does not develop the same trajectory.