Leg yield and shoulder in, part 2: the aids

The way I see it, the aids are the same for leg yield and shoulder in. In both movements the horse goes sideways with more or less angle, and with more or less pronounced flexion of the neck (see my previous post).

Order of priorities
When you teach your horse a new movement, or for that matter, when you introduce a new exercise to a rider you should follow this order:
1) The horse must be light in the hand (free to place its head and neck any way it wants), the rider must not hang or pull on the reins
2) The horse puts his feet more or less where you want (you have influence over the horse's balance), the rider can control the placement of the horse's feet
3) The horse, through the yielding of the jaw and relaxation of the poll and neck, lets its head fall into a more or less vertical position (the horse is in the form), the rider does know how to ask the horse for this yielding of the jaw and relaxation of the poll and neck

The hand is the primary aid
What I mean by the statement “the hand is the primary aid” is that the attention to the quality (ie lightness) in the contact between the rider´s hand and the horse´s mouth is always the top priority. It comes before everything else. To see the hand as the primary aid does not mean that I try to force the horse around with large uncoordinated gestures. Not at all, quite the opposite. To see the hand as the primary aid is to acknowledge that lightness between my hand and the horse's mouth is the main indication of the movement's quality in general.

I have previously written about how to educate the horse´s mouth and also how to influence the horse´s balance by the use of the hand.

The legs
Since the word “leg” is present in “leg yield”, it is of course easy to assume leg aids are necessary to perform the movement. Since only the angle in which the horse is travelling seems to differ between leg yield and shoulder in, the same could be true for the latter movement.

You can of course use your leg to ask the horse to move sideways. If you do, there are a few things you should keep in mind:
1) when you use both legs at the same time, it is a signal to the horse to move forwards
2) a single leg tells the horse that it will move sideways and not forwards
3) when using your legs, either together for forwards movement, or to move the horse to the side, the horse should not lean or push on the bit

A single leg can be used to ask the horse to move sideways. Spontaneously, I think most of us imagine that an increase in pressure from one leg will cause the horse to move away from that leg. This is one way to train the horse. But how much pressure is needed? A horse can feel a fly crawling on its skin, so the answer must be "not very much". Instead of focusing on increasing the pressure in the leg that is on the horse, you might be better off easing the pressure with the leg that the horse should move towards. If you pay close attention, you can feel the horse's barrel lifting your knee up in one sequence of the horse´s foot fall when stepping sideways. You can very easily lighten the contact of you leg against the horse´s side by aiding in the lifting of your knee at this very moment. Do not hold your leg up, but let it sink when the horse's barrel sinks and then lift it again in time with the horse's movements. If the horse does not perceive or understand your cue, stimulate the horse gently using a whip on the opposite side. And, of course, pay attention that your horse does not start to lean or push against the bit.

The weight
If you want to help your horse by using your weight, you want to place your weight in the direction of motion. This means that in a right shoulder in on a straight line where the horse moves to the left, your weight should also be placed to the left. Using your weight as an aid is done by extremely subtle means and it is easy to do too much.

Do nothing
Remember, when the horse does what you asked for, it is your job to do nothing, ie to be the best, non-interfering passenger you can be to your horse.

Thank You
Thanks to Mark Stanton of Horsemanship Magazine for checking my spelling and grammar! All other errors are my own.