The Crimping Chronicles: A few pointers
It should come as no surprise that the hand tops the list for most injured body part in rock climbers. They don’t look impressive, because they lack the bulk and obvious power of larger muscles like the biceps, or quads, but they are capable of holding more than your body weight against gravity. It is a huge feat, and I am going to discuss how it is almost designed to fail at the worst possible time.
Our flexor muscles, sinewy and long, start at the softer, inner side of the forearm, and taper into thin, strong tendons as they run into the hand. That is why when you feel “pumped”, you feel it in the forearm and not in the hands. They allow us to grip and curl our fingers - an absolute necessity when climbing. Seems pretty simple?
Feast your eyes on this engineering marvel.
The top drawing shows a finger, finger pads facing up. The flexor tendon that runs along the top of all the bones is being held down by 5 annular pulleys, labelled as A1-5, and 3 cruciform pulleys, C1-3. These fibrous nets hold down the tendon along the bone, which allows for the tendon to efficiently transfer forces from the muscles in your forearm into finger movement. It is an elegant design. If you were to remove one of those pulleys, you can imagine how the tendon would bowstring out, and there would be a loss in movement precision, and a lack of power.
Of the 5 annular pulleys in the finger, the strongest and largest is the A2 pulley. It is capable of withstanding outrageous amounts of force when placed in demanding positions like a crimp. (Nerd Alert! There is a scientific definition for what the crimp is. It is when the last joint of your finger is extended, or bent backwards, while the joint next to it is curled inward). This is a strong, static position that harnesses the mechanical advantage of this pulley system. You might have even been crimping without noticing it because it is just that efficient.
But with great power comes great responsibility.
Unfortunately, the A2 pulley has some trouble living up to its role as “Strongest Pulley” because it is the most likely of the 5 to be injured while climbing. As I mentioned at the top, this system, for all of its au naturel mechanical engineering glory, has some characteristics that make it more likely to fail while climbing. However, those same characteristics might actually make climbing more energy efficient.
How can it be both a blessing and a curse?
Well, like a good episode of LOST, I think I have answered some questions, but have left many more unanswered. In my next post, I will get into the injury mechanism for the A2 pulley - it has more to do with our evolution as humans than I would have thought. Super interesting stuff and I can’t wait to share it. Stay tuned.
