Typing has been linked to carpal tunnel syndrome

Researchers from Temple University in Philadelphia say tests on rats show highly repetitive actions may damage tendons, ligaments and bones.

Experts have been divided over whether repetitive tasks like typing can by themselves cause this damage.

Writing in the Journal of Bone and Mineral Research, the scientists say their study could help industry and medicine to tackle the problem earlier.

Physical damage

As many as two out of three people who suffer work-related health problems damage their tendons, ligaments or bones.

They can go on to develop osteoarthritis, tendonitis or carpal tunnel syndrome, where tendons or ligaments in the wrist become enlarged or inflamed.

Our studies have shown a direct relationship between repetitive, low force movement and the inflammation of muscles, bones, nerves and connective tissue Dr Ann Barr, Temple University

However, many experts have expressed doubts over whether people with these conditions developed them solely because of work.

They suggest underlying medical problems or activities at home may be to blame.

Dr Ann Barr and colleagues decided to carry out tests on rats to see if highly repetitive tasks were enough to cause them physical problems.

"Because multiple factors play a role in the development of work-related musculoskeletal disorders, including work tasks, home activities and medical conditions such as diabetes or heart disease, we studied work tasks alone to isolate their impact," said Dr Barr.

They found highly repetitive tasks did cause damage to the rats. Many reduced their movements or avoided the task completely.

"Our studies have shown a direct relationship between repetitive, low force movement and the inflammation of muscles, bones, nerves and connective tissue," she said.

"These behaviours increased according to the rate of repetition. The higher the repetition, the more severe the symptoms."

Dr Barr said that the rats appeared to pick up injuries relatively quickly.

"Carpal tunnel syndrome usually takes a long time to develop, yet we started seeing evidence of tissue damage within three to six weeks.

She said the discovery suggests that action can be taken to avert these injuries.

"This finding suggests that we may be able to intervene earlier in the development of the disorder and prevent further, more severe damage," she said.