When A Little Twinge Means Big Problems: Avoiding RSI 

Could you be doing irreparable damage to your hands and wrists simply by working at the computer for a few hours every day? It may sound like an exaggeration, but for some people even two hours per day of steady typing can cause serious physical problems. The culprit? Repetitive strain injury (RSI)—a condition that can damage the nerves, tendons, and muscles of the freelancer's most basic tool—the hands. RSI can affect the arms, elbows, shoulders, back, and neck. Recovery can require months of rest and physical therapy; for some people, the damage is severe enough that they may never be able to use a computer again. The Bureau of Labor Statistics reports that 332,000 new RSI cases are diagnosed each year.

Milite, George A. Editorial Freelancers Association (1997). Articles>Human Computer Interaction>Ergonomics>RSI