It refers to the connection between your leg aids and your rein aids, specifically your outside hand and your inside leg. Typically, your outside rein should support your horse and allow him to give into the bit while your inside leg should be driving your horse into the bridle by engaging his hind end, sandwiching him between your leg and your hand.
From inside leg to outside rein
Posted by Irina Yastrebova on Wednesday, August 3, 2016 07:55 PM
Recently, I had a light bulb moment when it comes to the phrase - "from inside leg to outside rein". This phrase is one of the most used ones when it comes to dressage training. And I bet everybody has their own view of what it means to have your horse connected from inside leg to outside leg. My moment happened when I was watching my instructor Sharon Merkel-Beattie ride my horse for the first time since I started lessons with her 3 years ago. Clearly my understanding of the concept of "inside leg to outside rein" was wrong. Watching her ride and listening to her comments was very much an eye opening experience plus I got on Santo after and felt the results of Sharon's work.
When the horse is truly in front of inside leg he doesn't run from it, doesn't stiffen or ignore, or fall into it. The horse lifts through the ribcage, the back and whithers and that lift is felt in outside rein. The horse steps more actively, more under himself because of the lift and neck becomes rounder ad longer. Outside rein becomes a framing rein that can shape the energy of the lift into more compact arc of collection or a little longer arc of extension. It can direct the horse to go straight or to turn.