Teach your horse to be reactive to the sideways leg aid in the same way that you teach him to react to the forward driving aid. That is:

  1. Give a light aid.
  2. If he ignores you, make a correction.
  3. Go back to what you were doing originally and RETEST with the same light aid.
  4. If you get a 100% hot-off-the-leg reaction, praise.
  5. If not, correct and retest again.

Now let’s teach your horse to react to the leg that’s behind the girth by doing the following:
Ask for a leg yield in the head-to-the-wall position where the front legs are in the track and the hindlegs come to the inside at about a 35-degree angle to the wall.

So let’s say you’re tracking to the left. Walk straight down the track. Counter-flex at the poll to the right.

Slide your right leg behind the girth to ask him to move sideways. Don’t push with it. Train him to go sideways more from the position of your leg as opposed to the pressure of your leg.

If he ignores you or doesn’t give you enough angle, tap him with the whip or bump with your leg in a way that makes him go sideways as opposed to forward. (That’s one of the reasons you do this exercise in the head-to-the-wall position. The “wall” helps prevent him from running forward. So does your left rein.)

Then RETEST!

Straighten him. Then slide your right leg back again. If he immediately moves his hindquarters sideways, praise him. If not, correct and retest.

If he just isn’t “getting it”, try using an opening right rein and give a very small squeeze with your right leg at the same time. As long as you keep his neck straight with your left rein, the action of the opening right rein (right hand brought directly to the right) will cause him to swing his hindquarters in. Then you can praise him.

Once he fully understands what you want, you can eliminate the need for the opening rein and active right leg and go back to the refined aid of asking him to go sideways from the position of the leg behind the girth.