What might a channel-surfing couch potato have in common with marathon-running exercise fanatic? Both individuals are at risk for knee osteoarthritis, according to a new study presented at the annual meeting of the Radiological Society of North America (RSNA).

Both rare and frequent exercise accelerated the degeneration of knee cartilage -- a trigger of knee osteoarthritis -- in middle-age adults, according to the study by researchers at the University of San Francisco (UCSF). Nearly one in every two people develop by the condition by age 85, according to the Centers for Disease Control and Prevention.

The study used questionnaires to follow the exercise habits of 205 patients between the ages of 45 and 60 over the course of four years. Researchers used magnetic resonance imaging (MRI) to measure a specific biomarker -- known as T2 -- that tracks the correlation between exercise habits and knee cartilage degeneration.

By gauging so-called "relaxation times" on the biomarker, scientists can collect data on cartilage water content and collagen structure. "If the water content is increased and the collagen structure deteriorates -- these findings indicate cartilage degeneration," noted Dr. Thomas Link, professor of Radiology and Chief of Musculoskeletal Imaging at UCSF, in an email interview.

Study participants who exercised vigorously one hour a day, three or more days a week, experienced increased T2 measurements, which Professor Link said, “suggested poorer cartilage health.” Participants who rarely exercised experienced similar results.

Researchers are still unclear as to what an optimal level of physical activity might be, although a previous study found that, “moderate exercise like walking, playing golf, etc. less than two hours per day for three or more days per week was associated with the best cartilage health as measured with cartilage T2,” Professor Link explained.

While the results of this study might seem initially depressing for exercise fanatics, researchers hope that T2 technology will help them determine how to reverse the impacts of extreme exercise such as marathon running.

“T2 relaxation time may also show cartilage damage that is still reversible,” Professor Link stated in an email. “It shows findings before cartilage is lost or there are cartilage defects, which are irreversible.”

Earlier on Huff/Post50:

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