You use seat, leg together with rein aids to leg yield your horse whether on a diagonal or on a circle.
The aids used for leg yielding over on the right diagonally (say, from quarterline to long side) or straight (such as when you track right at the long side and intend that the horse’s front legs stay on track and its hindquarters move in the direction of the arena’s middle).
The seat: Make sure you are sitting square over your horse’s middle.
If you should lean leftward over the leg to the rear of the girth your leg signals are contradicting those of your body weight. You need to go through these exercises to help you to learn how to sit square:
• Sit on a halted horse. Remove your left foot from the stirrup. Staying upright, make like you are about to dismount down the right side (don’t actually dismount, though). Repeat a number of times so you get muscle memory. You should be able to feel all of your weight descending into your right iron, while your hips move right.
• Imagine a seam running bang down the center of your saddle from cantle to pommel. To move your horse right in your imagination, envisage raising your seat bone on the left and moving it atop the central seam.
The legs: Your right leg should go as follows:
• It is passive on the girth, to get forward movement.
• It becomes active in that it should be used to do a couple of squeeze/ release cycles if your horse should start backing up.
• While leg yields are on, the horse must go forward 50% and sidewise 50%. If he over achieves sidewise, like say 75%, you activate your right leg and ask your horse to move further forward.
The left leg is used as follows:
• It is used to ask for lateral movement. Move it between three and four inches to the rear of the girth.
• If the horse fails to move sufficiently sidewise, your left leg activates by squeezing and releasing two or three times till the horse moves further sideways.
The reins: The leg yield position of your horse is such that he has a straight spine, but is flexed away from the movement’s direction at his poll.
The left rein functions as follows:
Turn your left side wrist like you are turning a doorknob to get poll flexion.
The right rein works this way:
You hold it steady; it should support in a side-rein fashion and maintain the horse’s neck straight.
While increasing a circle’s size in leg yielding, the position of your legs becomes different. The inside leg rests on the girth and the outside leg is to the rear of the girth, since leg yields necessitate that your horse’s spine is straight (which by implication means bent on a circle along the circle’s arc).
Your horse should be able to tell without mistake that you want to proceed sidewise in a leg yield, not stay on the circle, by your weight shift as also by the direction of your eyes.