The Crimping Chronicles: Lock and pop

Previously on The Crimping Chronicles

The tendons in our hands can efficiently produce movement and grip thanks to the simple design of the pulley system. The A2 pulley, which is located around the fleshy part of the finger just past where the finger attaches to the palm of your hand, is one of the strongest. However, it is also the most likely to be injured. Why is that?

Before we get into how most climbers damage their A2 pulley, we need to look back at the evolution of humans. There are some physical characteristics that humans display that harken back to our time as tree dwellers. One of those is how the flexor tendon and the sheath that surrounds it (including the pulleys) interact with each other to make gripping, specifically gripping to hold your bodyweight against gravity, more energy efficient. This is also found in the animal with the best hang time - bats.

Typically the purpose of a sheath is to make tendon gliding as frictionless as possible. Imagine a well with a bucket full of water at the bottom. If the rope was covered with grease, it would move smoothly to pull the bucket up. But if you had to hold its position steady part way up, it would require a lot of energy to not have it slip back down the well. This is where yet another ingenious piece of anatomy comes into play.

The flexor digitorum superficialis, one of two major flexor tendons in the hand, and the A2 pulley have little ridges that lock into one another in certain positions, kind of like a zip tie. When we curl our fingers in space, there is minimal friction, but when we lock into place under weight, the friction between the tendon and the pulley suddenly increases, allowing you to sustain that position with decreased muscular effort. This is referred to as the tendon locking mechanism.

This explains why the crimp is so strong and why you are likely using that grip subconsciously on smaller holds. The combination of increased force production based on the biomechanics of the crimp hold PLUS the increase in friction between the tendon and pulley make it an efficient way to hold on for dear life.

But it comes at a cost.

Let us revisit the zip tie example. Imagine you have one that looks like the image. If you wanted to open up the zip tie with only your hands (assume you now have the strength of the Incredible Hulk), would you try to pull it apart slowly or quickly?

Slowly probably won’t get you anywhere. It is, after all, locked into place. Your best chance of breaking that sucker would be a high velocity pull that generates enough power to overwhelm the structure.

If you have been following along closely, you might notice that I normally don’t point something out unless it applies to the topic. Meaning, it should come as no surprise that the most common mechanism of injury for a pulley involve quick, high velocity, unexpected force demands.

Examples, which all assume you are using a crimp, include: a sketchy foot slipping out from under you, a dyno to a crimp with poor preparation, repeat crimping whilst fatigued. (I always wanted to use the word whilst but the right moment never came up until now).

That sickening sound is unmistakeable.

POP

In our next installment (don’t worry, these reads should get shorter, but I am not promising anything), we will talk about everyone’s favourite accessory - tape! What is the purpose? What taping style is best? Is it even effective or does it merely serve the purpose of giving you street/rock cred like a participation award? Tune in next week to find out!