8. People who use computer keyboards——some of whom make as many as
21,600 keystrokes an hour—account for some RSI (repetitive strain injury) cases
that result in lost work time. Before computers came along, typists would stop to
make corrections or to change paper. These motions had the effect of providing
many small rest breaks. Today, computer users must devise their own minibreaks
to prevent excessive use of the hands and wrists that can lead to RSI injuries. People who use a mouse for more than a few hours a day-graphic designers, desktop publishing professionals, and the like—are also showing up with increased
RSI injuries.