The single-rein stop is one of the most useful rein aids we have.  In our English world we also have a pulley rein which differs widely from the single-rein stop.  Both rein aids are to control the horse’s forward movement and bring his legs back under control.  I am a huge fan of the single-rein stop for various reasons and all of our horses know it and learn it very early in their training.  Having done a lot of problem horses, it is also one of the first things we teach them. 

Let’s talk about how to properly do a single-rein stop.  The best way to teach horse and rider is again to do it in a walk, where everything happens slowly and methodically.  For my students who don’t know a single-rein stop, I prefer putting them on one of my horses who already understands and can follow a single-rein stop properly.  Then I teach them on their horse who does not know this.  Walking your horse with a soft connection or on the buckle, you will slide one hand halfway down the rein toward the horses’ mouth, and then quietly bring that rein gently back towards a point somewhere between your hip and shoulder on that same side.  The opposite rein is not part of this exercise, and remains neutral, meaning there is a loose connection and certainly no communication on that rein.  The educated horse will immediately follow that pressure and elongate the outside of his body, and shorten the inside, maybe take a couple steps turning towards that pressure, but then immediately soften through his body and jaw and will stop walking.  At that point the pressure in the rider’s hand hopefully can soften through the elbow toward the horse’s mouth proportionately to the horse’s give, which rewards the horse for that proper response. 

Now this looks totally different with an uneducated horse who might be stiff in their body and quick in the movement with their feet.  You still go through the same steps of sliding the hand halfway down the rein towards the horse’s mouth, but you might need a little bit more determination to bring that hand back toward your body.  Your horse’s first response will most likely not be to yield, but to lock his jaw and brace his body against you.  That will force him to start stepping in circles to try to get away from the pressure.  You will feel the pressure in your hand increase, while the horse is trying to figure out how to get out of this situation and get back to feeling soft and comfortable in his body.  At that point it just turns into a patience game again, and remember your opposite rein is not part of the exercise.  As the rider, your body energy stays neutral, there are no legs involved, it is not happening on your timeframe, but on the timeframe of the horse.  So have a cup of tea, hum a tune, and wait for your horse to figure it out, but at no point yield with your hand until the horse has stopped movement in his legs and yielded through his body which results in softening at the jaw, and a release of the pressure in your hand.  That release immediately gets answered by a softening of your elbow to the horse’s mouth.  At that point, you should feel the horse taking a deep breath, and his body relaxing, and he will most likely be licking and chewing, which is the moment when you praise him by stroking him generously on the neck.  Now your horse’s body should be in the same shape as the well-trained horse: elongated on the outside of the ribcage, shortened on the inside of the ribcage and yielded to your hand and the legs are standing still.

Horses are usually stiffer on one side than the other, so it might take a few more repetitions on the stiff side for the horse to understand what you are asking him to do.  What we are looking for is the horse yielding his body through a bend and softening through the ribcage after the feet have stopped moving.  As long as the feet are still moving, he is looking for a different solution than the correct one.  Very often the rider thinks that pulling harder on the rein or doing something with the legs should be the answer to helping the horse stop.  The horse has to figure out how to stop by yielding to the pressure in the rein without any additional information coming from the rider other than patience and softness.  Most of the time when you first start doing this with a horse it can take them quite a long time to figure out that the only way out is to soften.  You will find that with every correct repetition your horse will catch on sooner and sooner.  On my well-trained horses, all you have to do is slide your hand down the rein, and the horse already knows what is expected of him.  

This is an incredibly valuable and useful tool for training any horse especially for re-directing the legs if the horse thinks about dialing up the flight instinct and taking off.  Using the single-rein stop teaches my horse to bring his withers up and his head down, which relaxes his body.  This is essentially what I want the horse to do with whatever I am asking in my other training.  Most of the time, riders want to use both reins and pull straight back, which I absolutely hate.  The reason I don’t like that is because by pulling straight back on both reins, I am now engaging all the wrong muscles.  I am creating a stiff horse through the topline rather than a soft horse, plus this way my horse can out-pull me any day.  Remember, everything you do on a horse leaves a memory, good or bad, right or wrong.  My goal is to always do right by the horse and use tools and training methods which leave him soft and supple, rather than stiff and tight.  Pulling back on both reins will force the horse to lock his poll, use the underside of his neck, drop his withers, and brace against my hand, which are all muscle and behavior responses I really don’t want and certainly don’t want to train.  Whereas in the single-rein stop, my horse has to lower his neck, bring up his withers, relax his poll, and engage his ribcage on both sides. 

You will want to practice this quite a bit on both reins and you’ll want to get to the point where your horse will understand your intention and intuitively give you the correct response.  Be sure your horse understands how to do this properly in the walk and in the trot before proceeding on to asking for the single-rein stop at the canter.  Once you are doing it in the canter be sure you use the single-rein stop on the leading leg, so that you do not throw the horse off balance.  (i.e. If your horse is cantering on the right lead, use the right rein for the single-rein stop and vice versa.)