repetitive strain injury

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Damage to tendons, nerves, and other soft tissues that is caused by the repeated performance of a limited number of physical movements and is characterized by numbness, pain, and a wasting and weakening of muscles.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun pathology injury to muscles and tendons caused by continuous repetitive use of particular muscle groups, especially in one's arms and hands, for example by using a keyboard and/or mouse, playing a musical instrument or working on an assembly line