As a preparation for lateral work the exercise known as yielding to the leg may be practised in order to make the horse undersatnd the effect of the rider's legs pushing sideways. But the importance of yielding to the leg must not be over-rated; it should be used only to teach the young horse to understand the rider's leg aids. Unfortunately in recent years the contrary is often the case when practising equitation. This auxiliary aid has taken too great a part in the German instruction for cavalry. The Spanish Riding School has always used this yielding to the leg only to a limited degree, recognizing its original purpose.
[he then describes how and why to teach the turn on the forehand, and concludes that it should never be asked for in a dressage test]
Yielding to the leg will be made easier for the horse by giving his head more position to the opposite side, that is to say, when yielding to the left, the position should be more to the right.
When the young horse has learned in this manner to answer to the pressure of the rider's leg by stepping to the side, the yielding to the leg should be practised only when in motion in order to consolidate the understanding of these aids. At the Spanish Riding School it is practised in the walk only and disapproved of at the trot. It seems illogical that the horse should be taught to go sideways and forward with exactly the opposite position to that which will later be demanded of him in the half pass.
As soon as the young horse is obedient to the sideways pushing action of the rider's leg, the rider may start to practise correct lateral work.Correct lateral work, to Podhajsky's mind, is the succession of shoulders in, travers, and renvers. He goes into great and loving detail about each of these exercises, how they work the horse's body, how they are to be ridden correctly, and what they do to benefit the horse in its progression toward the haute ecole movements.
On the one hand: Podhajsky always backs up his advice with good reasons, and when you think about it the shoulder in works many of the same muscle groupings and gets at the same things that a leg yield does.
On the other hand: Podhajsky's goal in this book is to build a horse in the correct classical dressage way, and the leg yield is not a classical dressage movement. He's referring to a broader body of work, and his method is half scholarly erudition and half military precision (he was, after all, a career cavalry officer until World War II). Training a horse is like painting a masterpiece, and extraneous brush strokes are not necessary.
So taking that into account, Podhajsky is working from the blank slate of an impeccably bred and well-started young horse. He doesn't (at least in this book) talk about working through physical deficits of an older horse, or a mis-trained one, or a less talented one. (He writes eloquently about those horses in My Horses, My Teachers, but that book is not the training manual that this one is.)
I think he has a point about moving on to the shoulder in, and I'll try and start working that in more. Mastering a corect shoulder in, and building the muscles to do so, will address many of the problems that we're working on with the leg yields: a more supple hind end, more controllable shoulders, keeping straight, and keeping rhythm through it all.
Does anyone have any other thoughts about leg yield vs shoulder in?