Apple PowerBook (2400c) - Manual (Page 126)

Keyboard and trackpad
m When you use the keyboard and trackpad, your shoulders should be
relaxed. Your upper arm and forearm should form an approximate right
angle, with your wrist and hand in roughly a straight line.
m You may have to raise your chair so your forearms and hands are at the
proper angle to the keyboard. If this makes it impossible to rest your feet
flat on the floor, you can use a footrest with adjustable height and tilt to
make up for any gap between the floor and your feet. Or you may lower
the desktop to eliminate the need for a footrest. Another option is to use a
desk with a keyboard tray that’s lower than the regular work surface.
m Use a light touch when typing or using the trackpad and keep your hands
and fingers relaxed. Avoid rolling your thumbs under your palms.
Some computer users may develop discomfort in their hands, wrists, or
arms after intensive work without breaks. Therefore, it’s a good idea to
change hand positions often to avoid fatigue. If you begin to develop
chronic pain or discomfort in your hands, wrists, or arms, consult a qualified
health specialist.
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126 Appendix A