In dressage, your horse has an inside and an outside when you ride him—but these terms have a different meaning from what you might imagine. Here’s how it works in dressage.
By Jennifer O. Bryant
In dressage, the terms inside and outside are used to indicate the way your horse’s body is positioned. Let’s say that you’re riding your horse in a circle to the right (clockwise), as shown in the illustration. To be aligned correctly, the outline of his body from poll to tail should appear to conform to the arc of the circle. His neck will flex laterally, slightly to the right. In this movement, he is said to be bent slightly to the right.

As you continue to ride in a clockwise direction, you can see the inside of the circle to your right, while everything to your left is outside the circle. But what really determines which side is inside and which is outside is the direction in which your horse is bent or flexed. In this case, he’s bent to the right, and so right is inside while left is outside.
And this is where the concepts of inside and outside can get confusing. Let’s say you’re riding around the perimeter of your ring to the right (clockwise). Ordinarily, you’d expect that your horse would be flexed laterally and bent slightly to the right, especially as he travels through the corners of the ring. In this case, as in the circle example at right, inside is his right side and outside is his left side. However, there are some dressage movements in which you’d actually position him to the left, with his neck flexed and his body bent slightly to the left, as shown in the far-right illustration. In this case, inside and outside are the exact opposite. Inside is now the left and outside the right. So if you were doing this exercise and were told to shorten your inside rein, you would shorten the left rein.

Your horse always has an inside and an outside, no matter where he is relative to the arena rail — and even when there’s no rail at all, such as in an open field. The appropriate designation is determined not by his placement in space but by the way you position his body.
Excerpted from The USDF Guide to Dressage © 2006 by Jennifer O. Bryant. Used with permission from Storey Publishing.