I've had this information on paper for a while now, but feel it's good insight to share into fencing and what the horse has to consider. I had a friend who shows non pro read it over to make sure it made sense. I've mentioned in another post that my responses when training horses are reflexes, and all of these insights written below are a nano-second of thought for me. Horses are more than just a tool to do well at a show. They are individuals and some want to have their own way of doing things. Understanding how horses process situations, and getting in the saddle and practice pen, will build confidence in riders to build the relationships with their horses. When the relationships are built, the team works as one to accomplish whatever the goals may be.
In my program, fencing is for only one main purpose - teaching a horse to run, correctly. This could also be said as correcting the way a horse is running. The first time I ever showed at a NRHA show I watched, a lot. I remember seeing a guy running and stopping, and stopping, and stopping for most of an hour. The horse could really stop, well - probably 30 feet - every time. It peddled with the front feet and was soft in the face. I wondered to myself "what more can that horse give?" I was pretty young at the time and didn't have a complete stopping program of my own. I now have an appreciation for consistency. A horse has to stop a lot, a whole lot, to really master it.
When a horse runs to a stop there is a lot going on that they have to think about - lead, rate, speed, balance, stay off the rider's legs, how far to run, listen for the word 'whoa', don't anticipate, compensating for the rider on their back - it's a long list. Once the horse hears the word 'whoa' there is another list of things they have to consider - don't push on the bridle, lift my shoulders, don't lean right or left, keep my shoulders up, get my hocks under, push hard, stay soft, finish stopping, do I stay, or back, do I turn. This can give a human thought process to the horse; add in an unbalanced rider and the list can take on a survival mode.
Let's remember what a stop should be. For me, stopping is a by-product of a good transition from forward to reverse. You have to have a good backup in order to work on any kind of stop - soft in the bridle, elevated shoulders, 'break' in their back, drive with their hocks. You want a transition to the stop/reverse. Saying 'whoa' activates the transition. Say 'whoa' with slack in the reins. If the horse misses it, then you pull. It's a command to back, not to stop - you're loping, you're loping, you're loping, ('whoa') then you're backing; it's a continuous motion. Say 'whoa', but expect the reverse. You're after consistency. Your enforcement comes after the 'whoa'. If you're fair and consistent, your horse will learn something good.
I often use a circle or rectangle to work on stopping. I feel that all of these different things that the horse has to think about are best considered by taking momentum, speed, resistance, and anticipation out of the equation. I take all the time needed to get the full list of things a horse needs to have right before asking for the stop.
Let's get back to fencing. The running part of the stop is what fencing is about. It's about picking apart the horse on a straight line. The stopping is the maneuver. Once you're in the maneuver you can't change anything. What your horse is doing in the line, or approach, is where you need to pick on them or work on fixing what needs fixed. Stay off the rails when practicing. Your horse is learning how to be on a straight line. Keep the stop about the reverse. It is form and function. Think back up.
One of the biggest things I tell my students is how to stay out of their horse's way. Lots of people try to practice timing. I find that difficult. My advice is, from the start of your run, drop down on your tail bone; drop your shoulders back and keep them back; drive with your legs. When it comes time to stop release your legs and say 'whoa'. If you change your body position at that moment, it doesn't work. Do it well in advance so it's out of the way. Release your horse from the run and let them stop.
What you do immediately following the stop determines what your horse will learn. If your horse is bracey on the front end, their shoulders are not soft or elevated, correctly. Trotting or turning your horse in the bridle until they are soft and elevated, again, is a good place to start. If your horse doesn't slide, it's a good bet that it's the backup that needs work. Remember, soft in the face, elevate the shoulders, drive with their hocks. Get in the saddle and enjoy the rides!
For the rectangle exercise, that was mentioned, read the post How To Build the Stop Without Stopping.