Repetitive work tasks linked to bone damage

While experts disagree on whether work tasks alone can be the exact cause of work-related musculoskeletal disorders (WMSD) such as carpal tunnel syndrome, a new study by researchers at Temple University proves that a highly repetitive work task, a risk factor for WMSD, does in fact cause bone damage.

“Because multiple factors play a role in the development of WMSD, including work tasks, home activities, and medical conditions such as diabetes or heart disease, we studied work tasks alone to isolate their impact,” said Ann Barr, P.T., Ph.D., associate professor of physical therapy at Temple University and the study’s lead author. “This information is critical in helping industry and medicine establish workplace guidelines to prevent WMSD.”

The study, “Repetitive, Negligible Force Reaching in Rats Induces Pathological Overloading of Upper Extremity Bones,” published in the November 11 issue of the Journal of Bone and Mineral Research, is the third in a series conducted by a group of researchers at Temple University’s College of Health Professions and School of Medicine. “Our studies have shown a direct relationship between repetitive, low force movement and the inflammation of muscles, bone, nerves and connective tissue typical of WMSD,” said Barr.

Work-related musculoskeletal disorders, including carpal tunnel syndrome, osteoarthritis and tendonitis, make up the majority (65 percent) of all occupational illnesses and cost industry tens of billions of dollars each year.

To show how the tissue damage caused symptoms of WMSDs, the researchers analyzed behaviors in rats such as decreased movement performance and task avoidance. “These behaviors increased according to the rate of repetition. The higher the repetition, the more severe the symptoms,” said Barr.

While the researchers were not surprised by the nature of the tissue damage or the resulting behaviors, they were surprised by how early it began. “Carpal tunnel syndrome usually takes a long time to develop, yet we started seeing evidence of tissue damage within 3-6 weeks. This finding suggests that we may be able to intervene earlier in the development of the disorder and prevent further, more severe damage,” said Barr.

Currently, the group is studying the effects of increasing or decreasing repetitive tasks on both tissue and behavior. They have also begun to determine markers of inflammation in patients with known WMSD.

“Future work will examine the long term effects of repetitive motion and the power of ergonomics or medication in preventing or lessening tissue damage,” said Barr.

This research is supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIH), the National Institute of Occupational Safety and Health (CDC), the Foundation for Physical Therapy and Temple University.

In addition to Barr, the research team includes faculty members at Temple University’s College of Health Professions and School of Medicine: Mary Barbe, Ph.D., associate professor of physical therapy; Brian Clark, Ph.D., assistant professor of physical therapy; Steven Popoff, Ph.D., professor and chair of anatomy and cell biology; and Fayez Safadi, Ph.D., assistant professor of anatomy and cell biology.