The outside rein on a circle - the right technique
Hello. What a great question. Learning what to do with the outside rein, and how, is one of the hardest things to master in your communication with the horse. I think you will get different answers depending on who you ask.
When you influence the horse there are a couple of things to keep in mind. One is how you do it; the other is making sure the horse understands what you mean. We can give as much influence as we like, but if the horse does not understand what it means the aid will soon stop meaning anything to them.
So what is the role of the outside rein in a turn? The riding manual describes it as restraining and regulating. In practice, on a leading rein aid with the inside rein, the outside rein keeps the horse from bending its neck too far to the inside. The influence must stay soft and never come backwards. So, to answer your question, the hand stays put, but the rein must not go slack or the aid becomes unclear to the horse. Once you have established a soft, elastic contact with the horse's mouth, gently closing the hand should be enough, though this depends on the situation and how schooled the horse is.
A good first step is to practise following softly with your hand and arm in walk, keeping a soft, elastic contact from the elbow. When you want to turn, try taking both hands a little softly in the direction you want to go. This is only to feel what happens, not how you should ride once you have found the feel. Experiment a little, but keep that soft, elastic contact, never hard and never slack.
Another way to practise is to take a bit with reins and have a friend hold the bit as if it were the horse's mouth. Ask them to move their hands back and forth as in walk. Practise following the movement and turning.
Once you have a good, soft contact with the horse's mouth and the horse is "on the rein", it can be enough to drop the shoulder on the side you want to turn a little further back. This puts more weight onto the seat bone on that side, creating enough bend through the horse's barrel for it to flex the same way, and you automatically get the right contact on the outside rein.
