RSI stands for Repetitive Strain Injury. In the present discussion, I will concentrate on RSI as it occurs to computer users.
A quick primer on RSI:
- An activity that causes "strain" produces microscopic tears or damage to your tissue.
- To counteract this, your tissues are able to repair themselves at a certain rate.
- You get RSI when the rate of damage exceeds the rate of repair for extended periods of time.
- The prevention and treatment of RSI completely revolve around decreasing the damage rate and increasing the tissue repair rate.
decreasing the damage rate.
Reducing the RSI Damage Rate
For many people, RSI seems to be a mysterious illness. Some people seem to be able to type all day, every day, without suffering ill effects. Others seems to develop strain and suffer permanent damage incredibily quickly. Most people do not know what really causes RSI, and if you don't understand the causes, it makes virtually impossible to apply a good prevention or treatment plan.
The damage you get from typing depends on a variety of factors: the number of keystrokes, the force you apply for each keystroke, the angles of your joints, the pressure on your tendons during each keystroke, etc. Why is this the case?
To understand the damage rate, we need to understand how the damage is incurred in the first place. Once you know how damage is incurred, it becomes easy to identify things that can increase or decrease the damage rate through logical reasoning without having to memorize a
list of "dos and don'ts".
The Mechanics of RSI Damage
To really understand RSI, it helps to think about the hand like a
mechanical engineer. Do an image search for the internal structures of
the hand. You'll see that the finger tips are connected to the
forearm with many individual tendons. The muscles that pull on these
tendons are located in the forearm, which means that the myriad of
tendons have to wind their way through tunnels and pathways in the
wrist in order to connect to the muscles in the forearm. When you
curl a finger, a certain tendon is being pulled by its forearm muscle.
Likewise, when you extend that finger, a different tendon on the
opposing side is pulled by its forearm muscle. The combination of all
the tendons and their muscles provide us with all the intricate
movements of our hands.
You can think of the finger tendons like thick nylon ropes. The
rope, by design (actually by evolution) can withstand tremendous
amounts of tension without sustaining damage. For most people, your
forearm muscles will give out much sooner than the tendons will snap.
However, in most causes of RSI it is precisely the tendons that cause
the problems in the first place. So what causes the tendons damage
when they are so strong?
Recall that tendons are like a thick nylon rope being pulled through
the tunnels and pathways in the wrist. The damage to the tendons do
not occur due to the tension on the rope itself; they occur due to
the friction between the tendon and its surrounding tissues.
Imagine pulling a nylon rope back-and-forth repeatedly through a cable
guide (such as a pipe). If the cable guide is perfectly straight, you
can keep pulling the cable back-and-forth without the rope sustaining
much friction damage.
Imagine, however, that the cable guide makes a sharp, 90 degree bend
in the middle, and the same rope is being pulled through this guide
back-and-forth repeatedly. The nylon rope will quickly fray around
the bend and will eventually snap. Alternatively, the cable guide itself could be worn down and become damaged.
In the case of the carpel tunnel, you can think of it as a whole bunch
of independent ropes sharing one cable guide, each being pulled
back-and-forth repeatedly, while the amount of "bend" in the cable
guide depends on the degree to which your wrists are bent or twisted.
As you can imagine, with many tendons gliding back-and-forth in a
tight tunnel, it's hard to predict exactly which tendons or which
tissue areas get damaged by any particular motion.
Tactics to Reduce RSI Damage Rate
Now that we understand the mechanics of RSI damage, here are some
practical tactics for minimizing the damage rate as well as the
rationale behind them:
- Most important rule: DON'T DO ANYTHING THAT HURTS
If doing any particular movement causes pain, STOP. The pain indicates that you are past the point of "strain" and are actually causing acute trauma. If you persist on activities that cause pain, you can rapidly push yourself into severe injury and disability. IT'S NOT WORTH IT. - Don't type or mouse unless necessary
Don't be an idiot and play computer games all night after working all day on the keyboard. If you derive your livelihood from using a keyboard and mouse, you should think carefully about whether you can afford to keep tearing up your tissues for non-productive tasks.
Anything you can do to reduce the number of keystrokes would help. For example, reduce keystrokes with macros or a better editor. - While typing or mousing, keep your wrist posture as neutral as possible
Avoid any flexion, extension, or deviation in any direction: palmar, dorsal, ulnar, radial, etc., and avoid twisting your wrists. It should be clear by now that having your wrist bent drastically increases the amount of friction damage as your tendons glide through the bends. - Do not rest your wrists on the "wrist-rest" while typing
Besides often inducing dorsiflection, resting on the wrist-rest compresses the "cable guides" and causes each tendon movement to generate more friction damage. - Do not wear wrist-braces or "ergonomic gloves" while typing
Most wrist-braces and "ergonomic gloves" end up applying more pressure on your "cable guides" and actually cause more friction damage if you are actively using your hands at the time. Wear wrist-braces only when you're not actively using your hands (such as while sleeping).
An extension to this is that if you wear heavy or constrictive watches or jewelery, take them off when you are typing or mousing. You want to allow your tendons to glide as freely and as frictionlessly as possible. - Minimize finger movements; use arm movements instead
Since much of the damage is caused by the friction on the tendons, you can minimize the damage by minimizing the movement of the fingers. So, instead of moving your mouse with your finger tips, move your whole forearm instead. Likewise, don't stretch for keys by making exaggerated motions with your fingers; instead, move your entire hand towards the key, and only use the fingers to press down on the key.
A corollary to this is to avoid making compound-keystrokes with one hand (especially far-off combinations like Ctrl-G). Doing so requires you to twist and stretch your fingers and wrist into unnatural postures. This causes unnatural movements that require the tendons to glide through convoluted pathways and incurring more friction damage. Always use both hands to make compound-keystrokes, ideally pressing only one key per hand. - Keep your hands warm while typing
The natural fluids that provide lubrication between the tendons, joints, and their surrounding tissues are drastically reduced if your extremities are cold. You should be able to feel clearly that your hands are "stiff" when they are cold. Do not type or mouse under such conditions.
Do whatever it takes to warm up your hands before and during computer use. Stretches, rinsing with warm water, hot beverages, push-ups, ski jacket, space-heater, whatever. The only exception to this is that you should not wear gloves while typing (see above). Instead, warm up your core sufficiently so that your extremities are naturally warm with good circulation. - Use a keyboard that requires minimal key travel and minimal required force for registering a keypress; likewise for a mouse
Sometimes these two goals oppose each other. For example, typing on a solid plate of glass (like a touch screen) requires minimal key travel but imparts massive shocks on your fingers for each key and would not be ideal. I personally prefer keyboards whose keys are "light and crisp"; the crispness makes it clear exactly how much force is required to register a keypress, and avoids the problem of having to press with extra force just to ensure the keypress. You should definitely try out a few keyboards to find one that best suits you.
A corollary to this it to use as little force as possible in registering keypresses and mouse clicks.
That's all I can think of for now, but hopefully once you understand
the mechanics of RSI damage, you will be able to assess for yourself
whether a particular action, posture, or device is conducive to the
reduction of the tissue damage rate.
I will get into the mechanics and tactics related to increasing the
tissue repair rate in an upcoming post, The Prevention and Treatment of RSI, Part 2: Increasing the Tissue Repair Rate.
