Tuesday, May 12, 2009

Ergonomics and you

Man blogging consistently is harder than I thought it'd be. T__T
So here I'm going to repost something I wrote a while ago, but updated, and with references included. Maybe it'll get the juices flowing again.

As a philologist, I enjoy breaking down the words we use, both rarely and every day. Perhaps in examining the roots and history of why we speak the way we do, there is meaning, or even understanding, to be divined.
Like many of our technical terms, ergonomics comes from Latin. Ergo- refers to work. -Nomy is an interesting component, meaning something like law, or management. -Ics is a very dense little particle. It means the entire field of study; of art and science and knowledge.
A rough translation is "human engineering", which may explain my predilection for the field. :P
The best efforts of humanity are found in our efforts to better ourselves and our world.

Meta-lingual-discussion aside, I know I'm not the only one that spends a lot of time at their computer, so I thought a little guide to workspace ergonomics would be a useful post.

Starting off is the fact that while our knees, hips, and spines were good enough for our ancestors to survive, procreate, and provide enough for their children to grow up and repeat the cycle, selective pressure didn't give a crap if they would do so without giving us chronic pain into our dotage. Thus, they're all a bit fragile, and we need to take care of them if we want a comfortable middle and old age.

First things first, I recognize that few, if any of you, are going to run out and implement all of these suggestions immediately, but I'm putting this up as food for thought, a reference to check back on if you need to, and something to keep in mind if you get the chance to reorganize your work space.

Sit down work doesn't affect our knees so much, but humanity evolved legs in a world without chairs, so our spines and hips are a bit at a loss as to what to do with them.
Remember when you were goofing off in class, and kept tilting your chair back on two legs, tossing pencils at the ceiling or whatever? You thought you were just bored, but apparently we were unconsciously adopting the ideal sitting posture. If you spend more than a half-hour at a time working at your computer, You want your chair to support a 90° angle between legs and torso, and you want your torso tipped back about 35–45°. This way, the weight of your body is more evenly distributed, and you derive the maximum benefit from any lumbar and shoulder support the chair has.
However, you also want your feet on the floor, otherwise the weight of your legs is pressing your hamstrings right into the edge of your chair, which is a recipe for discomfort, and in extreme cases, even damage.

stick figure diagram
As you can see by my masterful art skills, there are pixels.

You also want to spend most of your time sitting perfectly evenly, shoulders, spine, and hips all aligned. Lateral stress on the spine can cause soreness in the back and hips. Arms should hang neutrally from the shoulders, ie, you shouldn't feel any stress or effort in your shoulders to keep your arms in position. Your medial plane should bisect your keyboard between the G and H keys (or I and D on Dvorak), and the exact middle of your monitor.
Now, craning your neck downward isn't, generally, good for you. Your spine forms a far-back fulcrum for all of your head's weight to wrench on. But here, you're leaned back, with your head straight up and down. The weight of your head is distributed into the head, neck, or shoulder rest, and you end up with even less weight on your spine than when sitting upright.
But if your chair lacks a headrest, this position might fatigue your neck muscles. This is a good time to point out another important ergonomic tip: switch positions. Though what I'm outlining is the best biomechanical posture, static pressure still has the potential to kink muscles, blood vessels, and nerves.
Of course, the best way to do this is to get up and take a quick walk every so often. But short of that, sit up straighter, or lean further back or pull one leg up, do something to change the forces affecting your body, and give pressure points a chance to recover.

Speaking of pressure points, viscoelastic memory foam is some nice stuff. It may not have been developed specifically for NASA, but they sure saw the benefits. The stuff that you now find in Tempurpedic mattresses was actually developed in Sweden, for hospitals. It is ironic (actually ironic too), that hospitals are one of the worst places to be when you're sick. Think about it, your immune system has been compromised, so let's stick you in a building with a lot of people carrying infectious diseases? Yay?
One of the features that used to compound this problem were bedsores. When you literally can't move, those pressure points get to be a serious problem. As in moisture builds up, making it a lovely environment for bacteria, which infest the skin, making raw patches, which continued pressure causes to become open wounds. Memory foam was created to alleviate pressure points completely, which is what makes it such a good material for beds, pillows, and yes, high end chairs. (You don't often see memory foam in chairs because you need a much higher density foam—ie, expensive—than that in mattresses, where your weight is more spread out, and pillows, where there's not much weight.)

So that's sitting. How about typing? Tendinitis and/or tendinosis of the wrists/forearms/hands is something most of us in this modern world deal with regularly. It happens because certain small movements, repeated over and over, can damage and possibly inflame tendons.
As a note, the carpal tunnel syndrome happens when pressure builds up in a small channel within your wrist. The pressure affects the thick nerve that controls your hand, and this causes general shooting pains through the hands, wrists, and forearms. For obvious reasons, tendinitis (inflammation of tendons) of the tendons in the actual carpal tunnel can cause the carpal tunnel syndrome. But while the picture painted by modern medical science is a touch murky, as far as I can find, it's generally believed that only certain twisting motions will cause an inflammation there. Basically, writing, painting and typing inflame or damage other tendons.
The midline of your keyboard should obviously be even with the medial plane of your body. Obviously, if your arms are angled in, your wrists need to be angled back out to put everything in the right position for typing. One wrist curved more than the other is obviously going to be under more strain. This is exaggerated on smaller laptop keyboards. Ergonomic keyboards are split so that your wrist doesn't need to bend at all. But if your keyboard is at the right height/position, the arrangement of the keys and of your fingers should not put a significant medial bend in the wrist. Still, couldn't hurt. Plus some of us have different length fingers than others.

You want your hands to be slightly higher than the elbows. If your fingers are on the home row, this position gives your fingers the a very neutral amount of curvature. Thus you require only minimal extension or flexion to hit the keys above and below. When you need to hit a key to the side (enter, backspace, tab, tilde, etc) try and do it with fingers and elbows, rather than wrist.

Mouse position is very important. Listen up WoWees. It's very very easy to try and sling your mouse around with your wrist. That's bad. Don't do that. Please.
With the keyboard in the right position, the best place for your mouse is on a slightly inclined tray right above your numpad. This lets you hold the mouse with zero wrist flexion, and move it smoothly from the elbow, which is ideal. I know that this is pretty hard to arrange. In fact, I've only seen one or two commercial products that allow you to follow this advice from the "famous" University of Georgia ergonomics study. But don't despair yet. Laptop users actually have a slight advantage here, in that they can just put their mouse pad where they need it. Left-hand mousers actually have it even easier! Just prop your mouse up immediately to the left of any regular keyboard, and you're good to go. If none of these are options, a slightly angled out, tilted up mouse-pad platform just to the right of your keyboard is the next best bet.
But whatever you do, don't rest your wrist or arm on anything, and move your mouse from the elbow, not the wrist.
On that note, remember that your keyboard and mouse are the parts of your computer you have real, direct interaction with. And furthermore, they sure don't go obsolete the way the internal components do. Get a good quality keyboard, and it'll last you decades. The IBM Model M clicky keyboard has a solid, tactile click that helps you put in only the amount of force you need, instead of grinding down on a plastic dome. Others have expounded upon their value, so I'll leave it at that.
Similar advice applies to your monitor, speakers/headphones, mouse, and something very few people consider in much detail: the mouse-pad. I'm not expecting to gain many converts to the world of expensive rigid plastic mouse-pads. A mouse sliding easily with the smallest possible impetus is a joy few know.

And finally, viewing.
Lighting is important, but it's pretty basic: minimize reflections and contrast.
If there's something reflected in your monitor, your eyes won't be sure what to focus on. They'll end up rapidly switching between what's on the screen, and what's reflected in it, and that's a recipe for eye fatigue. Similarly, if your monitor is dim, and the area behind it bright, or vice versa, you're (somewhat literally!) looking at eyestrain. You also really don't want any direct sources of illumination in your peripheral vision, as the rod cells in your eyes
This means that ideally, everything behind your screen is lit by indirect light to exactly the same illumination as the screen, and everything in front of it is perfect matte black.
For the real world, I recommend a torchiere (ceiling directed standing lamp), or maybe a lamp behind your monitor (credit Jessica), half-closed blinds, and an otherwise dim room. Modern CFLs are recommended for their energy savings and cool white light. If there's a significant amount of light reflecting off of or coming from you or the scenery behind you, and there's absolutely no way to move your monitor... you're screwed. Curl up and die.

Your forehead should be even with monitor's top bezel, allowing your eyes to cover everything in one sweep (you look down more naturally than up). You should be far enough back that you don't need to move your head at all, nor your eyes much, to see any part of the screen.

As for the screen setting itself, if you have a CRT, make damn sure it's set to a refresh rate higher than 75Hz. Anything less and you'll be lucky to avoid splitting headaches.
For both, your "contrast" setting should usually be at max, and the brightness at the lowest possible level where you can only just barely distinguish between black and the gray one standard step above it.

Set "contrast" to 100, decrease brightness to zero, then step it up until you can tell them apart.

This is recommended in a quite a few places, for text especially, and most games (I remember that Half-Life actually had a calibration screen that instructed you in this set-up). I think some artists prefer a little less contrast and more brightness for color fidelity? I don't have any references, but if it's that important to you, get a good monitor color calibrator, and follow its software's instructions.

Thank you. I hope this leads to a little less occupational stress for someone, somewhere. Please tell me if I've missed anything, or you have an issue with any part of this advice.

1 comment:

Robert Wheeler said...

Ouch. This is longer and more poorly written than I remembered.
Sorry anybody that's flailed through it.

Also, I seem to have forgotten the references I promised. Hrmm.