As published in The Guardian, UK RSI may cause sick worker syndrome Alok Jha Science correspondent There could be more to repetitive strain injury than meets the eye: scientists say the nerve damage caused by repetitive motion could be a cause of "sick worker" syndrome and such symptoms as poor performance, fatigue and depression. RSI is an umbrella term for disorders including carpal tunnel syndrome, tendonitis, tennis elbow and tenosynovitis. Caused by highly repetitive movements, such as typing, it affects some 450,000 workers in Britain. Symptoms include weakness or loss of sensation in the neck, shoulders, upper back, or hands. Ann Barr and Mary Barbe of the College of Health Professions at Temple University in Philadelphia studied the early changes in nerves caused by repetitive activities. They found the injuries are caused by the action of proteins called cytokines, which help start the inflammation. The proteins appeared in rat models of RSI within three weeks. As the injury progressed, more cytokines were produced at the inflammation site. The researchers found unexpected links between the production of cytokines and the rats' psychosocial responses. "At three weeks, even before the rats experienced pain from their wrist injuries, we watched them self-regulate their work behaviour," Dr Barr said. "With inflammatory proteins in the bloodstream, they began to slack off." After five to eight weeks, many of the rats curled up and slept between tasks. The researchers said people who took days off work owing to undefined symptoms or slowed down their work rate may be suffering from the effects of the raised cytokine levels. A low-grade depression may also set in. As the proteins appear soon after nerve damage first happens, when actual pain is rare, many people might not make the connection between the "off" feeling and possible RSI. It could take months before the nerve damage is bad enough to be noticed. Dr Barbe said: "Cytokines are self-protective. This undefined feeling of malaise may be telling the body to take some time off to heal, before things get worse."