The following reasons can cause a saddle to slide forward:
1. Very broad horse with a very flat withers
With these types of horses/ponies, the support for the saddle behind the shoulder is often equal to or wider than the shoulder itself. Saddles are often very on top of the horse so that there is no stop at the front. A Haflinger, Fjord, Welsh and Frisian fit into this picture.
2. Pear Shaped Horse
These are horses/ponies that have a deep and wide rib part. These horses often also have a downward rump with a horizontal neck onset. Horses often also walk with a high crotch. A Harrier and a Thoroughbred Arabian often fall into this category.
3. Horse's back use
These are horses/ponies with a tight back and loins. When these also bulge a bit, the saddle is pushed forward.
4. Very Belly Horse
When a horse has a very big belly, the girth will be pushed forward. The girth will then carry the saddle forward. An anatomical girth can offer a solution here. A built-in front girth (front strap) can also contribute to a good position of the girth without the saddle being pulled forward.
5. Horse has girth spot very up front
Every horse/pony has a specific place where the girth should be. (singel spot) People often say a hand's breadth behind the front leg. However, this can differ per horse. Some horses/ponies have the girth spot directly behind the front leg. The girth will also go here and take the saddle forward with it. An anatomical girth can offer a solution. A built-in front girth (front strap) can also contribute to a good position of the girth without the saddle being pulled forward.
6. A saddle that is too long
When the saddle is too long, the rear cushions of the saddle extend beyond 18e rib. These then rest on the loins. Besides being uncomfortable for the horse, this is also more the moving part of the horse/pony that pushes the saddle forward.
7. A saddle that is too narrow
If the saddle is too narrow, the saddle is too high at the front and often slightly set back. The saddle is therefore easily pushed forward over the shoulder by the rider/amazon and by the horse/pony itself.
8. Saddle with many wrongs
Because saddles are nowadays often performed with many wrongs, this is a recent cause. Rider/amazons work too much on the wrong, with the result that the saddle is pushed forward. Especially when the horse's training is more towards the collection and the rider/amazon will work more with the seat as a result, the saddle will slide forward earlier.
9. Riding style rider/amazon
Riders/amazons who ride behind the movement of the horse have a negative effect on the forward sliding of the saddle. The weight of the rider/amazon is in the back of the saddle, which means that the center of gravity is too much on the spoon. As a result, the saddle is pushed forward.
Combination of the above factors
In most cases, sliding the saddle forward is never due to just one cause. The combination of the horse's build with the rider's riding style makes this problem very complex.
In order to offer a solution to the problem of a saddle that slides forward, it is important as a saddle fitter to first rule out what cannot be the cause. When you can cross out these options, there are still a number of causes or combinations of these left. This will get you started.
It is too good to say that success is assured. There are always a number of cases where you have to come to the conclusion that without a tool it is not possible to leave the saddle in the right place. Fortunately, this is more the exception than the rule.