What would you say if I told you the difference in strength your horse requires to do a 20-meter circle and to do a 10-meter circle is almost nil? He needs to step under a bit farther with his inside hind leg and bend his hocks a bit more, but a proper, comfortable, symmetrical 10-meter circle isn't really a strength issue. It's a balance issue, and in this article I'm going to help you lay that issue to rest with one simple, effective exercise: a 20-meter circle that spirals in to a 10-meter circle, then spirals back out again.
This low-key, no-sweat, straightforward exercise will not only help you teach your horse balance; it will allow you to test that balance. And when and if he "fails" the test by showing you that he's lost his balance (I'll tell you how to recognize the signs), it'll be no big deal, because the exercise itself provides the cure. You'll never have to back off until he's stronger, more supple or more mature. You won't have to wait until you're more skilled or until a professional can help you. You won't have to quit because you and your horse are getting flustered or angry. And six months or a year from now, when you and he are making 10-meter circles look like child's play, this exercise will still be hard at work as a diagnostic part of your daily warm-up (Are you as balanced and supple as you were yesterday?) and a therapeutic part of your warm-down (Let's work on that lack of right bend you showed me today).
When is your horse ready to start this exercise? When he can stay evenly bent through his whole body (rather than bent in his neck alone, an all-too-common fault at Training Level) on an accurate 20-meter circle at the walk, trot and canter. His rhythm will be consistent, he'll be relaxed and his impulsion (or energy) will be strong.
Your horse should be able to maintain these qualities on his turn down the centerline (which is half a 10-meter circle), and neither fall, cut nor drift in or out on the turn—though I'd go ahead and start even if he's not quite perfect yet and your centerline turns have judges making such comments as "not enough bend," "bent to the outside" or "loss of balance." He may only be able to spiral in to 19 meters for a while, but he'll still improve his balance and his performance (and his test scores).
There's another very good reason to start this exercise early, too: Not starting to work on a figure until you need it is not good training; you'll end up rushing your horse so much that he'll lose what you're trying to help him learn. Start far in advance and you'll have all the time you need.
What Spirals In, Spirals Out
Pick up a rising trot and establish a 20-meter circle with all the qualities we've been talking about: bending, energy, rhythm and relaxation. Use the circle to run a checklist on your basic aids as well. Are you bending your horse and maintaining his forward energy with your very constant, very consistent inside leg? If he backs off or gets too quiet, are you squeezing your inside leg a bit more until he moves forward again? Are you supporting him and keeping him from falling out of the arc of the circle by holding your outside leg back? Are you keeping your inside rein very light to encourage him to step energetically under himself with his inside hind leg? When he bulges or falls out, are you momentarily opening the rein to guide him back onto the circle? And once he's there, are you lightening again? Are you keeping a consistent feel and creating your "diagonal aid" with your outside rein, receiving the rhythmic pushes from your inside leg, regulating his bend and drawing the size and shape of the circle? Good!
When you're satisfied with the quality of the 20-meter circle and your aids, begin spiraling in. Stay sitting in the middle of your horse and bring your inside shoulder back an inch or two to align your shoulders with his shoulders; that slight adjustment will automatically bring your hop back and weight your inside seat bone. Guide him just inside the 20-meter circle by opening your inside rein, bringing your outside rein across his neck (but not crossing it over the withers) and pushing rhythmically with your outside leg.
Return to a very light feel on your inside rein and continue gradually spiraling in, using your outside rein and outside leg to steer and push your horse over. Take your time. The object is not to race to the center, but to keep the consistent feel and the same basic qualities you developed on the 20-meter circle. Every step of the way, think about the quality of the circle, not the size. Ask yourself, "Is my horse correctly, evenly bent with good energy in his gait? Is he rhythmic and relaxed? Is his circle a continuous curve?"
Whether you spiral in a little or a lot, your horse is going to reach a point—maybe at 18 meters, maybe at 11—where the answers to your questions are going to change from "yes" to "no." He will have "lost it," balance-wise. How can you tell? The first sign, if he's a quiet horse, is loss of energy. He'll slow down. If, on the other hand, he's a bit hot, he'll get tense and you'll have lost relaxation. He may tell you he's uncomfortable by coming above the bit. He may fall on his forehand and get quick and heavy in your hands. He may lose rhythm. His trot may get so irregular that he almost looks and feels lame. He may fall out. And if he suddenly gets hard to turn and you find yourself toppling to the outside and pulling on the inside rein, he's saying, "I've had enough! I've gone as small as I can go!"
You could be creating at least some of the problem. Your horse may be falling out because he's unbalanced or because you're not supporting him enough with your outside leg. You may be spiraling in too acutely. You may be "motorcycling" by leaning to the inside, throwing him onto his inside shoulder and bringing your outside hand forward so your rein is loopy and ineffective. You may be turning him with your inside rein (he may have been successfully covering p for you during his half-10-meter circle turns onto the centerline, but he can't compensate long enough to stay balanced through the second half of the circle as well). You may be slowing him down (slower does seem to make smaller easier) and thereby sacrificing rhythm and energy—in which case you're not only not helping him master the exercise; you're negating the whole point.