The injuries sustained from mousing, in Sweden, are collectively called Mouse Arm Disease (M.A.D.). To gauge our risk from getting M.A.D. you need to understand some of the biochemistry of the body and certain aspects of the neurology of pain and the mechanics of our interaction with the tools we use. Muscles "do work" mechanically, biochemistry facilitates that work and neurology provides feedback and is the alarm system we rely upon. Any muscle that is tense is doing work and is therefore subject to the body's rules on biochemistry. When muscles are tensed they squeeze blood out, increase resistance to more blood being pumped in and also use up to 50 times more oxygen than when they are relaxed. So any activity that requires constant and muscle tension applied such as gripping, maintains this condition for that duration. See Working Postures. There are four primary physical aspects to mousing with most devices.

1. Holding your hand palm down tenses the muscles of your lower forearm.
2. Gripping the mouse between thumb and fingers tenses those muscles and muscles up and into the forearm.
3. Clicking mouse buttons adds extra tensile load to muscles and tendons already under tension due to grip.
4. Ulna & Radial Deviation. When mousing palm down, right handed, wrist movement to the left represents radial deviation and to the right, ulna deviation. The normal range of radial deviation is up to 20 degrees and for ulna deviation 30-50 degrees. The impact of this is that when mousing palm down a small, 10 degree, wrist movement to the left is actually 50% of radial deviation capacity, 10 degrees to the right 25% to 30% of ulna deviation capacity. Compare that to working in the "mid pronated" or handshake position. Firstly, there is no radial or ulna deviation, secondly the range for Flexion, bending towards the inner wrist is 80-90 degrees and Extension, bending towards the outer wrist is 70 degrees. Consequently, even though we do not advise bending the wrist to move the mouse cursor, but to use the whole arm, the same 10 degree movement when in this posture relates to between 11% and 14% of capacity or over 100% less compared to working palm down. In engineering terms, wear characteristics are typically non linear and so load (resulting in wear) increases at a great rate the closer you are to capacity!

For those who may have invested in the so called vertical mice you have solved the issues at 1 and 4 above, but you may have exacerbated the issues at 2 & 3. The reason being that you typically require more grip to stabilize vertical mice as you no longer have the weight of the hand on top of the mouse as you did in the palm down position. AirO₂bic mouse provides the best of both designs as the weight of the hand in the mouse provides stability while not requiring grip. One vertical mouse in particular requires more pinch grip, between thumb and forefinger, than any other device.

As external references to these issues, the American Association of Orthopaedic Surgeons, amongst many things, advise the use of minimal grip and the US Government, under Section 508 Law, have set standard that say specifically:

Desktop and Portable Computers (1194.23) Updated: August 1, 2001

Subsection: (2) Controls and keys shall be operable with one hand and shall not require tight grasping, pinching, or twisting of the wrist. The force required to activate controls and keys shall be 5 lbs. (22.2 N) maximum.

Currently (1/15/04) the AirO₂bic Mouse is the only conventional mouse asserted (by us) as meeting these standards and facilitating purchase compliance with Section 508 law. They are listed on the "Buy Accessible" guide of the government website; www.section508.gov.

Biochemically activity in the small muscles of fingers and hands alone is not sufficient to lower oxygen levels in the major blood vessels which would trigger an increase in heart and respiration rates so increasing the blood supply to deliver more oxygen and wash away toxins. It is possible for oxygen concentrations to fall due to continuous and repetitive periods of muscular activity and we likely periodically enter, biochemically speaking, a fatigue state. When we are performing obvious physical activities such as manual labor or exercise and we reach a fatigue state, we start to ache and tire, which are signals to us to take a break. However we do not seem to be aware of reaching a fatigue state when working at a computer, even though we often feel tired and get the aches once we stop. Research into migraine relief and pain suppression has now indicated something called Cognitive Distraction the ability of the brain (neurological system) to suppress pain signals when we are pre-occupied with "thinking" (cognitive) work. This could help to explain why we do not notice the aches while we are working and suggest too that better break management is important as well as improved tool design.

As things stand and without change there is a level of inevitably that all of us will experience some degree of symptoms and we will likely go slightly M.A.D.

The AirO₂bic Mouse™ and Virtually Hands FreeTM System remove all of the poor posture issues precipitated by using other mice, eliminating the need to grip and, on average, 95% of your requirements to click and potentially 100% of them. Mousing aerobically is our first contribution to a new generation of products that, by design, will adapt how we work, to how "we" work!

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