The middle-aged may risk arthritis and knee problems if they overdo exercising, a new study suggests.

Dr. Christoph Stehling (University of California, San Francisco) presented his findings to the Radiological Society of North America (RSNA) annual meeting. The study looked at people aged 45-55 (136 women and 100 men) who were asked about their exercising. They were then divided into groups of high, medium and low levels of activity.

The press release from the annual meeting explained that:

A person whose activity level is classified as high typically might engage in several hours of walking, sports or other types of exercise per week, as well as yard work and other household chores.

None of the participants had reported knee pain or other problems, but MRI scans showed knee damage in those who exercised the most. Neither age or gender had an effect.

Knee problems and joint pain are often associated with being overweight, but the participants in this study were all of a healthy weight.

Dr Stehling recommended that middle-aged people continue to exercise, but emphasised that high-impact, weight-bearing physical activity, such as running and jumping, may be worse for cartilage health.

Low-impact exercises that can build cartilage and help protect your bones include swimming, cycling, using gym equipment where your feet stay put (like cross-trainers and rowing machines), and yoga and pilates.