Repetitive strain injury, also called repetitive stress injury, is a loose group of conditions from overuse. It is an occupational overuse syndrome affecting muscles, tendons and nerves in the arms and upper back; hence it is also known as work related upper limb disorder or WRULD. The medically accepted reason it occurs is when muscles in these areas are kept tense for very long periods of time, due to poor posture and/or repetitive motions. There's also a connection between mind and the body, where pain is worsened or lessened by thought (see John E. Sarno).
It is most common among assembly line and computer workers. Good posture and ergonomic working conditions can help prevent or halt the progress of the disorder; stretches, strengthening exercises, massages and biofeedback training to reduce neck and shoulder muscle tension can help heal existing disorders.

Repetitive Strain Injury Association - London based association with a freephone helpline and a monthly newsletter for sufferers and those with an interest in RSI. Contact details available on the site.
Meta Description: [ The Repetitive Strain Injury Association. ]
RSI Mailing list - A resource and FAQ for people UK suffering from or concerned about RSI (Repetitive Strain Injury).