In the June 2010 EQUUS installment of Conformation Insights, Deb Bennett, PhD, discusses how a horse raises the base of his neck to produce an arch. In the exercise below, she describes how you can raise the base of your own neck in the interest of better understanding what you're asking of your horse.
Because it is important that the rider have a clear idea of what he is asking of his horse, this is an exercise I teach to every group of riding students. By doing it yourself, you will have the opportunity to experience what it feels like to your horse when he raises the base of his neck.
Sit on a bench or wooden chair, balanced and relaxed, and feel equal weight upon your seat-bones. Have both hands in your lap. Relax your shoulders and make sure you're not holding one or both of them up in a perpetual "shrug."
Now reach up to touch the top of your head. There is a certain zone where you will be aware that there is more "feel"--the so-called "crown chakra." This point will be on the midline of your head, and located rather closer to the back than to the front. Touch this point briefly to make yourself aware of it, then return your hand to your lap.
Next, imagine that you have a big, warm, sticky ball of pink bubblegum stuck atop that spot. The blob of bubblegum is as big as a golf ball.
Now, make whatever effort it would take to lengthen your neck enough to stick that blob of bubblegum to the ceiling. Of course the ceiling is a long way up there and you won't really be able to reach it, but you can try!
If you make the correct effort, your chin will automatically drop. If you feel your chin straining upward, you've got your bubblegum too close to the front of your head. Reposition it farther back. You should feel the back of your head "leading" as you stretch upward.
The back of your head is the human equivalent of the horse's poll, and we want him to move in the same way the bubblegum exercise causes you to move: by leading with the poll, pushing it forward and up. The poll leads because of the lifting effort of muscles located deep in its base.
How different this feels and functions than if I had merely told you to raise your head by pulling your "poll" back! If you want an idea of the discomfort it causes the horse when a rider attempts to obtain collection by pulling back on the reins, first pull your poll back and let your chin rise. Now, making the effort to hold your poll back, simultaneously try to tuck your chin. Don't do this for long or if you have pre-existing problems with your neck.