Layback Crack Climbing
A Physics Approach
The Crack
Layback
climbing is simple. It is also incredibly difficult. The
idea is to pull against against a feature (usually a
crack) with your hands, while pushing with your feet.
Here's an example:
Image credit: Stewart M. Green
Layback
crack climbing is not highly technical. In fact, when
laybacking there is only one choice you really need to
make: how high to bring your feet. This is where physics
comes in.
The higher you have your feet, the more force you will be applying perpendicular to the wall. This is where all that information on normal forces comes in. With your feet higher, you will be applying more perpendicular force, which will make your friction increase, meaning you will not slide down the wall so easily. Have your feet too low, and you may not have enough friction force to stop you from slipping. So why not simply keep your feet as high as possible?
The higher your feet, the more normal force there is, and the more friction you have. However, that same normal force that determines your friction is also trying to push you off the wall. This is where your hands come in. Your hands must pull hard enough to keep you stuck to the wall. So, the higher your feet are, the more force that your arms must apply. Having your feet high will tire your arms quickly.
So you want to keep your feet as low as possible, to save your arms, but high enough that you will get enough friction not to slide. Unfortunately, this ideal distance can't just be calculated. This distance is going to depend on the coefficient of friction of the rock for one. We discussed this in the forces section, but the better the coefficient of friction, the less force will be required to get an equal amount of friction, and the lower you will be able to place your feet. There are other factors as well, such as the pitch of the climb, the distance from the wall that your feet are placed on features that your hands grip, and your height.
I'm sorry I can't give you the perfect foot position, you'll have to explore that on every wall. However, I can give some other basic pointers (which I really just borrow from our newest sources, about.com and climbing magazine).
The higher you have your feet, the more force you will be applying perpendicular to the wall. This is where all that information on normal forces comes in. With your feet higher, you will be applying more perpendicular force, which will make your friction increase, meaning you will not slide down the wall so easily. Have your feet too low, and you may not have enough friction force to stop you from slipping. So why not simply keep your feet as high as possible?
The higher your feet, the more normal force there is, and the more friction you have. However, that same normal force that determines your friction is also trying to push you off the wall. This is where your hands come in. Your hands must pull hard enough to keep you stuck to the wall. So, the higher your feet are, the more force that your arms must apply. Having your feet high will tire your arms quickly.
So you want to keep your feet as low as possible, to save your arms, but high enough that you will get enough friction not to slide. Unfortunately, this ideal distance can't just be calculated. This distance is going to depend on the coefficient of friction of the rock for one. We discussed this in the forces section, but the better the coefficient of friction, the less force will be required to get an equal amount of friction, and the lower you will be able to place your feet. There are other factors as well, such as the pitch of the climb, the distance from the wall that your feet are placed on features that your hands grip, and your height.
I'm sorry I can't give you the perfect foot position, you'll have to explore that on every wall. However, I can give some other basic pointers (which I really just borrow from our newest sources, about.com and climbing magazine).
You can see the basic position from the image earlier. A few important things to note: it doesn't matter which hand you put on top, some prefer inside hand, some prefer outside. What's important to realize is once you get your hands in there, you won't be able to switch them (easily). You'll be going up in a shuffling manner, moving only one hand or foot at a time, and you should avoid attempting to cross them over one another. Making big movements is compromising, and larger progress will be made keeping the movements small.
Keep your eyes open for potential footholds that will reduce the strain on your arms. Even the slightest dip in the wall can change the direction of the perpendicular enough to make big differences. This change in perpendicular direction will help because part of the normal force will now be working to hold you up, rather than just push you away. This change of direction can be seen below:
Image credit: myself
There are a few other things to consider as well. Whenever possible, remain straight armed. This directs the force through your skeleton rather than your muscles. This is a general rule of climbing that should always be followed, not just for laybacks.
Even when your straight armed, your fingers and forearms will still be engaged to keep grip. You won't have much of an issue gripping a crack with your hands while laybacking, because the almost the entire direction of force is in the perpendicular. Keep this in mind, and try not to over-grip the rock, it'll save your forearms. To help out, try and find finger locks or hand jams that will allow you to hang and put the weight into your skeleton rather than muscles.
Here's one that sucks: no taking breaks. Do not attempt to "catch your breath" in the layback section. Your entire body is engaged here, and you will find no rest if you attempt to stop.
Finally, a logistics tip. If you're climbing with a lot of gear, such as if you're lead climbing, place it on your side away from the wall. This will keep it out of the way, and more accessible to grab.
Have fun, and climb on.