Sunday, February 12, 2012

Ergonomics, Part 2: Movement and Levers

This is a lot more specific than the first post on ergonomics. Before I get into this post, please note that I am not a medical professional. This is a basic overview of climbing movement as it relates to ergonomics; it's not a complete list, just food for thought.

In the last ergonomics post, we talked about pressure. Well, it's time for another physics lesson. This one's about levers. A lever is simply any object that has a load applied at one side, and rotates along another point, called the fulcrum. For now let's look at the simple version.

A basic, normal lever.

In climbing, levers are somewhat more complex, as the load is at one end of the fulcrum. This is called a third class lever, although most often you'll see the load at the other end of the arm, such as lifting a weight. In climbing, as other bodyweight exercises, the body itself is the load.

A climbing lever, such as an elbow.

The fulcrum is the joint, the load the body. For the purposes of setting, we'll view effort as being the climber pulling down on the holds, resisting gravity.

Elbow levers in action.

Note that this photo is very simplified - there are many more levers in play, including the wrists, joints of each finger and thumb, and knees. The hips and shoulders are more complex mechanical structures, with lateral and rotational flexion, but can be viewed much the same way as a normal lever - rotation is created by applying force to load at a pivot point.

Understanding how levers work in climbing technique is quite simple. Just raising the center of gravity on four perfectly spaced holds means that a lever (or levers, really) somewhere in the body must engage. For example, a beginner climber might use their arm as a lever. An advanced climber is likely to use their legs as levers as much as possible, because they know the size ratio of the involved muscles makes it a much stronger mechanism. This is where "twist-in" technique comes from - it relies on turning/bending the legs, and keeping the load off of the weaker lever (the arm) by keeping it straighter.

What's all this lever business mean for ergonomics? I'm glad you asked. A move becomes dangerous when the limb acting as a lever is hyperextended or hyperflexed. This endangers the joint mechanisms (fulcrums) which have to bear the most load. I'll talk a little bit about specific moves and how they can be tailored to be more ergonomic. In these cases, I'm usually talking about more static climbing or specific body positions. The ergonomics of dynamic movement are complex to a degree that I don't think I could cover it in a single blog post. Needless to say, any mainly dynamic movement is putting all of the involved joints at great risk, because the load is immediate, uneven and inaccurate. However, in a future post I'll go over some basic Dos and Don'ts which apply to both static and dynamic movement.

Vertical lockoffs are a simple example. Lockoffs are well-known for troubling elbows. In a deep lockoff, we see that the shoulder joint can quickly become endangered. Especially given most climbers' predisposition to an overdeveloped back and an underdeveloped chest, this can be a bad position. Also note that locking off on a deep hold like a sloper (or a very deep lockoff on a smaller hold) can put a lot of stress on the fingers and wrist. As the move gets deeper and eventually becomes a press, this wrist strain increases proportionally.

Avoid danger by: being aware of the angle of the shoulder and wrist levers when forerunning the move. Increase difficulty by altering the directionality of the source and target holds, rather than by adding distance. If distance is important, consider moving the feet upwards, or using larger footholds, to decrease the load placed on the endangered joints.

Gastons are a great case study for ergonomics, because used incorrectly they can endanger many of the upper body joints. Load is created at the fingers, and forced against the plumb line of both the elbow and shoulder. Straightening the arm to remove load is rarely an option, so we see even greater stress than usual placed on the elbows and shoulders. The further away from center mass the gaston is, the more load. A gaston far away from the body (overextension) will place extreme force on the fingers, shoulder, and wrist, while one closer (overflexion) will emphasize the elbow fulcrum. Gastons are notorious for a reason.

Avoid danger by: being cautious with dynamic movement on gastons. Use body position and foot placement to emphasize static movement. Gaston holds should allow a range of body positions - holds with extremely specific directionality will force climbers' fingers into strange positions to allow them to move vertically.

Underclings present a good, obvious case of hyperflexion and hyperextension. Like a gaston, an undercling that's too far away will require overextension of the muscles, placing great load on the joints. An undercling that is at chest height will require overflexed wrist, elbow and shoulder joints, and can be especially painful on the wrists.

Avoid danger by: Keeping underclings in the comfort zone between flexion and extension for the average body type. Adding an extra foot or two is a good compromise to allow the climber to find their ideal body position. Be wary of slopey underclings that must be held close in, as the body position range quickly becomes limited and climbers' wrists can get overflexed easily. Juggy underclings are less of a concern, because they allow the wrist to relax. In cases where a hold must be used like an undercling around the chest area, another option for moderate routes is to use a hold that can be meathooked (AKA monkey-wrapped, bugled, etc.) upside down, as it allows the wrist a more natural position.

High-steps ergonomically refer to any foot movement where the climber has to lean away from the wall, get maximum flexion of their hip joint, move a foot up high, and then load that foot. Performed wrong, this move places extreme stress on the hip joint, which can be dangerous to the lower back. In many high step scenarios, the knee may also be flexed past the point of safety, and loading it can be disastrous. High, heavily weighted heel hooks, especially overhead heel hooks, place similar stresses on the knee (not to mention being very muscularly asymmetrical.)

Avoid danger by: setting routes where unsequenced extreme high-steps are discouraged by practical use of feet. When high-steps are in the sequence, keep them closer to the center of gravity, respective of course to the intended grade. The rest is largely up to the climber's posture and ability to fire their leg muscles ergonomically, but you can gently push them in the right direction.

Kneebars can be painful, especially if set wrong. The nomenclature often leads climbers to attempt to jam their knee into a hold, when the action should really be happening in the thigh area. Jamming directly on your kneecap is dangerous for obvious reasons and I shouldn't even have to say not to purposefully set a "knee-cap-bar" type of move. Kneebars on the thigh, while notably more comfortable, can still be loaded to a degree that they become dangerous, especially when combined with extreme twisting to reach further from the locked position. Sharp kneebars on the thigh, while uncomfortable, are fine so long as the point of contact remains over the muscle and not near the patella.

Avoid danger by: using appropriately sized kneebars, leaving space for different size legs, and never overloading a kneebar in a twisted position. To generalize, kneebars should be used for body positioning and resting. Setting a kneebar as a way to extend static reach is possible, but should be meticulously forerun and tweaked.

Other quick notes:

Jams involving the fingers, such as hand jams, finger locks, ring locks, etc. are always going to have some inherent pain. It can sometimes be fun to use these moves indoors, and they can still be set safely. However, use them sparingly and mix up the hand/fingers used to avoid as much danger as possible. These positions are inherently stressful, especially on a gym population who are likely to have little (if any) crack climbing experience.

Heel-toe cams should always be set with a "dead man's handle" effect. In other words, it should be bomber only when the ankle is consciously flexed into position. A heel cam that locks by positioning only can be extremely dangerous, especially when coupled with dynamic, extended movement. The climber should have to focus to keep the cam, so there is no danger of the cam staying locked in during a fall.

Full extension upwards can be stressful on the back, ankles and shoulders. Often when trying to reach as far as possible, climbers hyperextend the tiny supporting muscles of the posterior chain. However, I consider this one fairly minor since routesetters usually know better than to set repetitive, body-size-dependent full extension moves.

This list is in no way comprehensive. The possibilities for movement might as well be infinite, and you shouldn't be held back by these precautions - just keep them in mind when setting. Climbers are taking a risk walking into the gym - your job is to reach a balance between danger and fun, not to minimize the danger to the point that the moves are homogenized. As always, take my advice with a grain of salt and think for yourself. And of course, the harder movement becomes, the higher the danger is. I highly doubt there is a V15 in the world which could be considered joint-friendly - but V15 climbers are the ones whose bodies are prepared for this level of exertion. That is your goal: the relative danger should match the difficulty and specificity of the move, so climbers can keep getting stronger and smarter.

For further reading on related topics:

Check out the book One Move Too Many. It is easily the most important climbing injury text I've ever read. Both for your own climbing and for knowledge on these subjects, I suggest finding a copy.

For more info on body mechanics, check out ExRx: the articles on levers and angle of pull would be good starting points.

I'll post again on this topic to go over some basic tactics for keeping climbers safe and healthy. Happy setting!


  1. As always... Such a good post. Keep em coming.

  2. Nice, Jesse! Good flow. Makes a lot of sense.

  3. Thanks for your hard work on such a great blog, keep it up.