From Wikipedia:
Repetitive strain injury (RSI) (also known as repetitive stress injury, repetitive motion injuries, repetitive motion disorder (RMD), cumulative trauma disorder (CT), occupational overuse syndrome, overuse syndrome, regional musculoskeletal disorder) is an injury of the musculoskeletal and nervous systems that may be caused by repetitive tasks, forceful exertions, vibrations, mechanical compression (pressing against hard surfaces), or sustained or awkward positions.
Types of RSIs that affect computer users may include non-specific arm pain or work related upper limb disorder (WRULD). Conditions such as RSI tend to be associated with both physical and psychosocial stressors.