Office ergonomics
Joel Spolsky has just posted a thing about the desks at Fog Creek’s new office. It uses an image that is often cited as being ‘ergonomic best practice’, but I can’t imagine a more horrendous way to spend a day in a chair:
(image borrowed from the Nicholas Institute of Sports Medicine and Athletic Trauma)
This seating position completely ignores the balance and weight distribution of a normal human.
What supports the arms and hands? Your muscles do. How do you think that feels after a day of work? Pretty damn awful. Hence, everyone I know rests their shoulders or forearms on an armrest or desk edge, or puts their wrists on a wrist rest. You just can’t hold your arms in that position all day without support.
A significant omission is the mechanism by which you support your hand/arm while using a mouse. Wrist injuries are another whole area which I’ve been lucky to avoid, but solutions include:
- arm weight goes on your hand (on the mouse), which leads to wrist strain and inefficient mousing
- arm weight goes on your wrist (on the desk), which leads to some twisting and nice callouses on your wrist
- arm weight goes on a wrist rest, which puts pressure on the tendons in your forearm (and exacerbates carpal tunnel issues)
I don’t know who they modelled this image on, but that is some damn fine posture they’ve got around the neck. I can’t keep my neck that straight when I’m standing. Maintaining this position requires quite a bit of tension in the rear neck muscles. Unfortunately, most of us also need to work on the desk occasionally and lean forward. This tires the neck muscles. The muscles tire, the head droops forward, the load on the muscles increases, and you go home with a sore upper back.
Again, this image is modelled on some imaginary human with very short upper arms. A significant problem that I have when setting up my own workstations is that to reach a comfortable table height, I have to compromise between squashing my legs (table lower) and having too acute an angle at my elbows (table higher). In fact, a fairly comfortable keyboard location is on my lap (and it solves the support-the-arm-weight problem to some extent).
Points 3 and 4 on the image are where your weight is supported. This just does not work. I cannot find a chair or a position in which this does not lead to numbness or loss of blood flow to some part of my legs. (Keep in mind that I’ve done quite a bit of long-distance cycling purely on my sit bones (3) and not had blood flow issues). The legs have some pretty serious blood vessels running through them and are moving in a normal human. Most people that I know move around through the day, and this helps a lot with blood flow. Keep in mind that sitting in an office chair all day is awfully like sitting in an airplane seat all day.
‘Feet flat on floor’ is another guideline which I find absurd. You can only reach this condition by adjusting the height of your seat. If you put it too high, the legs will be dangling and exacerbate blood flow problems at 3 and 4. If you put it too low, the legs will either be out in front and unsupported, or in the suggested position, under compression and throwing off the rest of your balance. This is an extremely fine balance to make, and completely incompatible with the idea of moving around in your chair during the day.
Most office chairs won’t go high enough for me to put my feet flat on the floor. I’m about 6ft/180cm, so while tall, I’m not that tall. The legs on most chairs will get in the way of your feet anyway, so this is a very unhelpful guideline.
Finally, the fact that you’re pushing against the chair at 1 and 2 means that your entire body is being shoved forward (Newton’s Laws strike again). The force must be balanced at 3, 4 and 7 (hence compression of the legs). Because you have nothing particularly good to push again, it’s all frictional, and you tend to slide forward in your seat. Then you’re a sloucher. One of us!
Enough complaining. What to do?
First, buy a good chair. You spent good money on a bed to be in for 8 hours/day; now you have to spend good money on a chair that you’ll be in for another 8 or 12 or 16.
I worked on an Aeron for a few months but didn’t like it. The mesh is too stiff for my bony butt and the whole thing is very heavy and difficult to adjust. I eventually bought a Steelcase Leap and am fairly satisfied. (It was also half the price of the Aeron in Sydney. Just watch the 8-week shipping.) No, it doesn’t have mesh, but I find fabric and some padding to be more comfortable. And you can choose colours!
Roughly, my setup is:
- Elbows rest on the armrests. This works way better than no support, but isn’t great. Some people use a towel on the desk to provide extra padding, and as a bonus it catches food and coffee ‘accidents’.
- Chair is high enough that I can either stretch my feet out across the floor or tuck them under and rest on the chair legs.
- Tilt varies through the day. I can either sit up if I’m working on the desk a lot, or recline back if it’s mid-afternoon and I’m cruising.
- Slouching is a no-no. If I’m starting to slouch, I tilt the chair back. I’m a hardcore sloucher.
- I use a Kinesis Contoured keyboard and strongly recommend them. They have big wrist-rest areas and supply with pads. Admittedly, I rely on this too much (the keyboard is designed to have your hands hovering) but it works fairly well.
- I use the mouse as little as possible. My geek is showing here, but I use a tiling window manager. This is a massive timesaver; there’s no fussing with window positioning and hence much less mouse use.
- I use a Standit to hold laptops up at eye level and Synergy so that I’m not reaching across the desk or shuffling keyboards around.
- I learned to mouse with either hand, since the joints of my right hand are fairly worn out after too much playing Quake. I wish I was joking.
I expect that each person is going to have a slightly different way to solve these problems, so please share how you approach these issues in your own office.