Anebel, could you please expand upon this? Is this in relation to collection? It is completely inverted from what instructors drill into us of inside leg to outside rein. If I'm reading it correctly, it involves using the outside rein aid before the inside leg aid and the not the other way around. Is that right?
When beginning the lateral work (SI here for an example), riders use so much inside leg that they push the haunches right out and off the line, and the shoulders over the outside aids as well. The result is an incorrect SI with ineffective outside aids and a more crooked horse carrying less weight on his inside hind - the opposite of that we want the SI to do.
By riding with the outside aids on and the inside leg relaxed at the girth, it allows the outside leg positioned behind the girth to keep the haunches tracking straight forward, and to keep the shoulder in line (that both shoulders are standing upright, no leaning to the outside) and then, the inside hind is forced to come under the horse's center of gravity and carry more weight.
I'm finding it hard to find video examples of each, mostly out of laziness. But you feel the difference between the horse pushing and carrying, and having effective outside aids and an effortless half halt in the correct way, and feeling the horse fall right over the shoulder and having no control the incorrect way.