I have some suggestions for the Letters page correspondent suffering from back pain (DW 11 September). My arm, neck and shoulder were strained and aching after a stint of long hours. The cure came via an article faxed to me by my brother.
These are the main points:
Get a good quality chair with adjustable height, back rest and tilt features.
Adjust the chair height until your forearm slopes slightly (90-100) from elbow to keyboard.
Have your feet flat on the ground.
Keep your wrists straight; and
Make sure you are facing your desk, monitor and keyboard squarely.
This worked for me within two days. I found sitting straight was very comfortable once I was in the right position.