hwood34: “Flat is better ergonomically”
metalliqaz: “My ergo desk at work is even tilted away from me so that it cancels out the modest incline that is built into the board.”
keyhopper: “Extended. But it depends on the height of the table and the chair, and the position of the keyboard relative to my hands and elbows.”
Melvang: “Neither flat nor extended is more ergonomic on its own.”
Sorry hwood & metalliqaz, but keyhopper and Melvang have it right on this one.
First, a disclaimer: I don’t claim to be an expert on this, (and to be honest, after reading a few dozen academic papers on the subject, I’m not convinced anyone is an especially reliable expert), but I have thought a bunch about it.
Expert advice / research is based on a few main concepts.
(1) Muscles shouldn’t have heavy static load. The typical goal is for long-term static load on any given muscle to be something like <5% of the maximum voluntary load (like what you’d get if lifting weights or similar). Many people have typing postures which lead them to have like 15–20% of maximum load constantly for hours at a time on certain muscles, e.g. in their back or shoulders. This is bad, leading to all kinds of problems.
(2) Don’t stretch hands/wrists/fingers into positions that will cause repetitive motions to take place at the limits of particular tendons’ range of motion. This leads to fatigue and inflamation.
(3) Don’t place excessive external pressure on tendons/nerves/blood vessels (there are actually a lot of places that you could put pressure on that would be a bad idea, spots on the upper back/shoulders/arms/elbows/wrists/etc., so be careful out there)
(4) Try to avoid excessive impact force / shock on the joints, especially repetitive impacts
Based on such principles, there have been a bunch of studies which tried to measure muscle loads and forces in various ways, but most of the literature is somewhat unsatisfactory and it’s hard to piece together a particularly coherent story. Much more research is necessary to settle many questions about keyboard design and use IMO.
But in any event, here’s my advice:
The best angle depends on the height of your desk and chair, the size of your body, and the way you sit.
You want to set your keyboard up so that you can sit comfortably, and type without putting excessive strain anywhere. That means, for any position you’re going to stay in for more than 20–30 minutes at a time:
- keep your shoulders, back, and neck in a comfortable relaxed position
- no shrugging, no hunching forward
- leave your upper arms hanging loosely down at your sides,
no sticking your elbows out or forward
- either sit up or make sure you have adequate back support.
reclining is fine, but no slouching
- try not to keep your head up; looking down a bit is fine,
but tilting the head too far down causes neck strain
(laptops in the lap aren’t great for extended use)
- keep your wrists as straight as you can get them. The further they get from
straight/neutral along any axis, the further certain tendons have to stretch,
and the more strain/fatigue results
- avoid excessive wrist extension or flexion
(= bending your wrists up and down)
- avoid excessive forearm pronation
(= rotating your forearms inward so your wrists are flat
- avoid excessive ulnar deviation
(= turning your wrist outward)
The standard keyboard is a pretty bad shape which makes it impossible to get your wrists in an entirely neutral position. (For that you need some tenting between split halves to reduce pronation, and some turn inward to avoid ulnar deviation). It’s possible though to avoid wrist extension/flexion, which seem to be the worst offenders (wrist extension leads to tendonitis and carpal tunnel syndrome).
The ideal case is to be in an environment where the home row on the keyboard is at or slightly below the level of your elbows, with the top of the keyboard flat or even slightly negatively sloped. However, even with a higher desk than that, it’s possible to avoid injury if you’re careful. I advise tilting your keyboard such that the key plate is parallel to your forearms when your wrists are straight. If your desk is tall relative to your chair, your elbows might end up bent fairly steeply, and the best keyboard tilt is also pretty steep; typing at a high desk puts a bit of extra load on your biceps, but luckily biceps are pretty strong.