The Proper Use of Draw Reins
Draw reins help a horse to use its body correctly by keeping its head down and its back rounded. Draw reins are used as an aid to the hand and reins, not as the reins themselves. Many people remove the regular reins and attach only the draw reins to the bit. This is wrong. When riding with draw reins, the regular reins are held as normal. The draw reins are held under the little finger and into the palm of the hands along with the regular reins.
The Desired Effect
Ride the horse as normal, and when the horse’s head comes up, use the draw reins to ask the horse to put its head down again. Once the horse puts its head down and rounds its back, slacken the draw reins, and go back to riding with the regular reins again. Yield the draw reins as soon as the desired effect is achieved. Give with your hands, and adjust the length of the four reins as you are riding.
Steady, Yielding Hands
The horse’s head will go up and down during the gallop as it tries to find a happy, not-so-painful medium in its new frame. Adjust all four reins quickly and adroitly to stay with the horse. This will get easier as you learn to handle both sets of reins.
Do not hold the reins rigidly with a fixed, set hand. This sets the horse up for fatigued and pulled muscles. If the horse’s energy is not allowed to flow, the tenseness the horse feels from the tight, unyielding draw reins will show up in other parts of the body. The horse must be given a break intermittently to let its muscles rest from being in this new position. It is the same as doing repetitions at the health club. You must rest between sets. Having the horse’s head cranked down into its chest with no chance of relief is unreservedly tyrannical. Some horses will refuse to go forward if the draw reins are shortened too much. The horse will spin in circles not knowing which way to go because its forward momentum has been thwarted.
Give with your hands and allow the horse to move forward.
A hallmark of horsemanship to remember is: Use the aids as much as necessary, but as little as possible.
Excerpt from How to Exercise a Thoroughbred Race Horse