Children's flexible bodies are in some ways more forgiving than those of adults. My kids can easily sit on the floor in positions that would give me backaches. For most children, it would take many more hours of cumulative trauma than it would for an adult to cause aches or tingling (this can happen, though -- it's amazing how long a kid can stay glued to a computer game without a break).

Of greater concern is the impact that improper positioning might have on growth and development. We know that bones continuously remodel themselves during childhood. This remodeling is directed by positioning, stresses, and the use of the bones (as well as the nutrients available). Consistent improper positioning can change the length and shape of long bones. While this hasn't been proven to come from computer use, I'm not aware that anybody has investigated the possibility.

Here are some of the basic lessons learned from ergonomics for promoting optimal health:

• Adjust the chair so you can sit with your feet flat on the floor and your thighs parallel to the floor.
  
  
• The monitor should be below eye level with the focus of attention between 1 and 60 degrees below the horizontal.
  
  
• Your desk or table should be about two inches lower than your elbow.
  
  
• Elbows should be kept at a 90 to 100 degree angle.
  
  
• See to it that there is good support for your hands and forearms when you are typing. You should be able to rest them on a tabletop, a wrist rest or the arms of your chair.
  
  
• While typing, try to avoid bending your wrists for any lengthy period of time. They should be kept in a neutral position -- not bent up or down or right or left.
  
  
• Don't hit the keys too hard. Try to develop a light touch, and adjust the keyboard to that end if possible.
  
  
• Neck should be straight, not craned over. Shoulders should be relaxed.
  
  
• Take breaks every 20 to 60 minutes, even for a minute or two. This is very important. Get up and move around. Avoid remaining in the same position for long periods of time.
  
  
• If using a mouse, avoid reaching for it with an extended arm during use.
  
  
• Mousing surfaces should be on the same plane as the keyboard and close to the user's body to eliminate shoulder strain and neck pain. Placing it on alternate sides of the keyboard each week, if possible, will lessen your dominant hand stress. Of course, frequent breaks from using your mouse are very important, as is avoiding long clicks.