http://klickfit.blogspot.com/2008/06/ergonomics-repetitive-strain-inj...

'RSI' is a general term for disorders that occur from prolonged,
repetitious use of the hands which results in pain, burning, swelling,
tingling, numbness, loss of dexterity and weakness. Other synonyms for
RSI include: Cumulative Trauma Disorder (CTD), Occupational Overuse
Syndrome (OOS) and Repetitive Motion Syndrome (RMS).

The more specific disorders are Carpal Tunnel Syndrome (CTS),
Tendonitis, Tenosynovitis and a host of others.
Of course CTS is the most common malady brought on by repetitive hand
motion.

Who is at risk?
The majority of RSIs are related to computer use, though other
repetitive work tasks, such as pipetting and heavy lifting, as well as
hand-intensive sports and hobbies such as knitting or playing a
musical instrument, can cause or aggravate an RSI. Working at a
computer puts you at risk for an RSI because part of your body is held
in a static posture while other parts move incessantly. Both static
postures and constant activity can cause first microscopic and then
macroscopic damage to biologic tissues. If allowed to progress, an RSI
can develop into a permanent disability.

Any combination of the following factors can lead to an RSI:

Repetition: The repetition of small, rapid movements, such as keying
or mousing, for long concentrated hours.
Static posture: Holding the same position, especially an uncomfortable
or awkward posture, for a long period of time.
Improper workstation setup: A workstation (table, chair) that cannot
be adjusted to position you properly and comfortably at your computer
or other work activity.
Force: Using excessive force to complete tasks.
Insufficient rest time: Intensive hours of working with too few rest
breaks to allow your body to recover from an activity.

Warning signs

RSI conditions have many varied symptoms. The following may indicate
the onset of an RSI.

Recurring pain (myalgia) or soreness in neck, shoulders, upper back,
wrists or hands.
Tingling, numbness, coldness or loss of sensation.
Loss of grip strength, lack of endurance, weakness.
Muscles in the arms and shoulders feel hard and wiry when palpated.
Pain or numbness while lying in bed. Often early stage RSI sufferers
mistakenly think they are lying on their arms in an awkward position
cutting off circulation.
Symptoms may be caused by apparently unrelated areas — for example
hand numbness may be caused by a nerve being pinched near the
shoulder. In the initial stages of RSI, an area may be in quite bad
condition but not feel painful unless it is massaged, or weak unless a
long endurance exercise is performed. Therefore all areas of the upper
body are considered when evaluating an RSI condition.