Thumbs on Top…But Do You Know Why?
Rider hand position is often discussed in riding books and by riding instructors. Many of us have been told to make sure we hold the reins with our thumbs on top, slightly pointing inwards. “Piano hands” (with the knuckles on top) or “puppy dog hands” (knuckles on top, wrist floppy) are well known “no-nos” when it comes to riding. When I first started riding I was told: “Thumbs on top!” but when I asked why, I wasn’t happy with the answer I got: “because it’s important.” Many people don’t know WHY it is important to keep thumbs on top. So let’s explore. It’s all about bones, muscles and tension.
There are two main bones in your forearm: the ulna and the radius. The ulna is located on the same side of your arm as the little finger, running from your elbow to your wrist. The radius is located on the thumb side of your arm. You can feel these bones if you palpate your arm. These two bones are connected to each other by a fibrous membrane. Hold your forearm down by your side and let it hang naturally. Raise your arm out in front of you so that the fingers point inward and the knuckle of the thumb faces up. Now turn your forearm so the palm faces downward; the thumb rotates inward. As you turn your arm, you activate two muscles that cause the radius and the ulna to cross over one another. See the diagram. One muscle that you activated (called the pronator quadratus) is located near the wrist joint. It pulls the end of the radius over the ulna as you rotate the forearm so the palm faces down.
You can feel the effect of activating this muscle when holding the reins. Hold your arms as though you are riding: upper arms hanging softly from the shoulders, elbows bent at about 90 degrees, wrists straight, hands softly closed around your imaginary reins, thumbs on top with a slight bend in the thumb knuckle. Become aware of your wrist joint. How does it feel? Don’t move the wrist joint, just take note of what it feels like. Now, rotate your forearm so that the knuckles of your fingers face downward. Now what does your wrist joint feel like? Most people will feel like there is more tension in the wrist, which comes from a combination of activating that pronator quadratus muscle and the crossing of the two forearm bones.
Achieving an elastic connection with the horse through the reins can only be achieved if we minimize the tension in our arms in such a way that the horse feels invited to take contact with us. Riding with the knuckles pointing down increases the tension in our wrist, which is communicated to the horse through the reins (whether they are attached to a bit or to a bitless bridle). This compromises our ability to achieve a harmonious connection. And that is why we must ride with thumbs on top.
Take away message for instructors: For many people, understanding WHY we ask them to do something is an important key to helping them figure out how to do it, and to keep doing it. Body awareness only comes when we understand how and why our bodies work the way they do.
Diagram is from Hermizan Bin Halihanafia. Anatomy Musculoskeletal: Radius and Ulna, Elbow and Radioulnar Joint. College of Allied Health Sciences. http://www.slideshare.net/hermizan84/shoulder-joint-humerus