Working Postures. (Designing to Functional Neutral.)
Muscles are "engines" that (in life) are never switched off. Typically, for every muscle that pulls one way there is another to pull back. In the hands the flexors muscles close fingers and extensor open them, so rest posture is a balance of tension between them. Just like a car engine we rev them higher to work them harder. If we can find a posture that allows muscles at risk to "idle" while we are still doing the same work then they are likely to give us years more problem free service than having them heading towards the red zone whenever we work. It is also true that a bigger engine employed at lower revs lasts a whole lot longer. This is why we have designed a mousing system that allows users to leave those "small engines", forward of the elbows, at idle speeds and use the, comparatively speaking, larger "V6 muscles", probably V24+ in comparison, of the upper arm to do the bulk of the work.
Functional Neutral as an objective is best appreciated from an understanding of differing working postures that ergonomics terms Static and Dynamic Postures.
Dynamic Posture (DP)
Is working under a regime in which muscles are cyclically tensed and relaxed; in our engine analogy, revved and allowed to fall back to tick over. Though this maybe very repetitive the fact that muscles are not under constant load (even if revved high) means that there is a rest interval in between each muscle tensioning event (what is called a Nano-break) so allowing for physiological recovery in which the muscles biochemistry gets a chance to fall back towards an equilibrium. Muscular contractions, in uninjured hands, typically aid circulation in limb extremities by acting as a pump. This is because when muscles contract they squeeze down on the blood vessels within them, forcing the blood out. When they relax the blood vessels open up and fresh blood is drawn in.
Keyboarding and clicking mice buttons is employing DP. It is believed that DP, on its own, is less likely to cause injury. A premise supported by the fact that old "mechanical" typists (their machines not them) were not so prone to these problems, though this should be balanced by the fact there were far fewer of them relative to the number of computer users today. The mechanical mechanisms of typewriters, being slow, meant typists took Nano-breaks between each character that they typed. They also moved their hands around more and had no opportunity to use wrist rests or drape their hands on hard surfaces and so their muscles became adequately developed for the task they had to do.
So DP and keyboarding is considered less as a primary factor in RSI though DP in the presence of injury will likely aggravate it and when DP is used to click mouse buttons, if in a Static Posture, it will put additional stress on already tensed muscles and tendons.
While I am sure that some will strongly debate DP complicity in RSI there is empirical proof that seems to go unnoticed; the fact that usually and predominantly the mousing hand becomes injured first and worst!
Static Posture (SP)
The most pernicious problem is believed to be SP, working under a condition in which muscles are tensed and held tense (continues above idle revs), which is the posture adopted when gripping computer mice. Any amount of grip applies revs to some extent beyond idle speed. When muscles are wholly or partially tensed (Repetitive, Negligible Force Reaching) they constrict the blood vessels that pass through them reducing the volume of blood in the muscle and increasing resistance to its flow and while tense do not allow their biochemistry to come back to equilibration.
Those who go for "burn" aerobic exercise are doing the exact same thing, pushing to the extremes of oxygen biochemistry so as to induce Lactic Acid Chemistry (LAC) to help burn calories and also build additional muscle. This relates to the muscle tone experiments that we conducted on computer mouse users. The difference is that you would only do this type of exercise for up to 40 minutes (and not continuously) a session and only 3 times a week. The time in between allows your body to react to the muscle tone development and develop more muscle mass and also to recover from the short term damage that will have been caused. When you are working under conditions that can potentially lead to low oxygen levels and LAC all day, everyday and with little recover time, then you can start to understand why problems occur. What we should be more surprised about is the fact that they do not occur sooner.
One irony due to blaming the keyboard is that software developers have switched much of their program functionality over to the mouse. Add to this the increasing dependency on the predominantly mouse mediated Internet for both work and hobby related activities then you have hour upon hour of constant grip, high revs and aching biochemistry that because of Cognitive Distraction can go unnoticed. Cognitive Distraction or "concentrating on what we are doing" is a circumstance that has been found to suppress the intensity of ache or pain signals experienced in the brain, it is used as a migraine management tool!
RSI is not a piston breaking, a total and obvious failure, it is a conspiracy of time, tools and work habit leading to an accumulation of damage to tissue cells that do not get a chance to heal and repair because we go back and repeat the same process day in and day out. Because we are so busy doing "what it takes to survive", "work", we need not notice the achy warning sign of the danger and so eventually chronic pain occurs both on and off the computer due to increasing injury. Eventually a "crash" occurs when an acute condition is reached, the point unfortunately at which most people, too late, do something about it.
In terms of a strategy for the avoidance of injury the best-known practice is that of Functional Neutral. Under Functional Neutral your biochemistry is close to idle speed with small muscles being at or near rest. In terms of a strategy for the avoidance injury the best-known practice is that of Functional Neutral. Under Functional Neutral your biochemistry is close to idle speed with small muscles being at or near rest. But this, in the case of computer mouse usage, requires working without gripping. Functional Neutral Posture objectives are easy to understand so measure and achieve. If Functional Neutral posture cannot be achieved, which may be the case with many technologies in the tools that are available today, then Dynamic Posture is the next method of choice though under a well managed break and rest regime. Static Posture should be avoided as a routine and continuous posture and in the case of computing and hands it can be avoided all together.
It isn't where your hands are in the air that counts:
It's where the air is in your hands!
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The AirO2bic Mouse design has been granted a U.S. Patent.
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