I've always called moving backwards when I'm on the ground 'backing-up; but moving backwards when I'm in the saddle as a rein-back.
Anyway, I'd say that it should be introduced early on but used in a different way depending on the level of schooling.
All horses should understand a rein-back. I use it for movements such as working around gates or moving out of the way of obstacles.
If the horse is further on in their schooling I'd use it for collection, to lighten the front and engage the rear in all disciplines and as part of a dressage test.
Anyway, I'd say that it should be introduced early on but used in a different way depending on the level of schooling.
All horses should understand a rein-back. I use it for movements such as working around gates or moving out of the way of obstacles.
If the horse is further on in their schooling I'd use it for collection, to lighten the front and engage the rear in all disciplines and as part of a dressage test.
