“Don’t start collected work until the horse is going forward with impulsion"??
The purpose of collection is to prepare a horse to carry a rider safely with maximum ease and efficiency and minimum wear and tear. Therefore, I don’t agree with the notion that you shouldn’t ask a horse for collection unless they are going forward with “impulsion”. If a horse is not supple or strong enough for a certain degree of collection, they may be able to go fast, but they are also not supple or strong enough for impulsion.
Impulsion is the expression of power that comes from collection. True impulsion feels like a release to a powerful thrust from balance, (not a push with the legs and a hold with the hands), and balance can only be achieved through true collection.
Collection is a posture: the lifting of the forehand and the increased weight bearing of the hindquarters. It is not a compression, but a shifting of weight off the front and towards the back.
I teach collection through slow therapeutic walk work, in-hand, nurturing a soft body and mind, straightness and self carriage, interspersed with much stretching.
The type of stretching is important as well.. the stretch is a controlled release, and belongs to the horse, who seeks the stretch once the body is released through correct work. It is not a posture that is specifically taught to the horse - I don’t teach the horse to lower the head or come into a stretched posture of my choosing. If stretch isn’t offered, I work more on softening and aligning the body until the horse finds release. Stretch and pick-up are fluid and encourage mobility, not fixed headset of any type (including long and low).
Using only walk work, I have rehabilitated horses with cow hocks, sway back and kissing spines, ewe neck, and transformed countless horses from hollow and sore to soft, graceful and happy. In all cases, the desire to move forward improves dramatically when the horse is first allowed to slow down and then shown how to carry themselves.
I do allow the horse to express their forward energy: a relaxed canter up a hill under saddle, a loose trot on a trail ride, a small amount of free trotting on the lunge or loose in the arena if they desire.
However, if the horse has lost, or not yet found, their desire to move forward, I find that they will find it more willingly, easily and naturally if I allow them to go slow while I gently show them how to align and straighten their body. In this way, even horses that have been labelled slow and unwilling find their willingness and forwardness naturally, without ever having to be pushed or driven forward.