How much exercise is a good thing?
Preliminary results of a 4-year study have shown that too much exercise, like too little exercise, can be associated with knee cartilage degradation as seen on MRI. Cartilage degradation is the first step in development of knee osteoarthritis.
In this study, 205 people without knee pain at baseline, who exercised at various intensity levels were followed over 4 years as part of a study at the University of California San Francisco. MRI-based T2 relaxation times were used to assess knee cartilage degradation over time. The preliminary results of this study were presented at the Radiological Society of North America Meeting this year.
MRI findings revealed higher knee cartilage T2 progression in the highest and lowest exercise levels than in the middle exercise levels. High physical activity was defined as one hour of vigorous physical activity, three times or more per week. All people enrolled in the study were at risk for osteoarthritis of the knee based on family history, obesity, or history of injury to the knee.
These results suggest that a moderate level of exercise may be optimal in preserving the cartilage in the knees. Exactly how much exercise this is, is still unclear.
Wilson L. High levels of physical activity are associated with greater cartilage degeneration over a period of 4 years as assessed with T2 relaxation time measurements – 3T MRI data from the Osteoarthritis Initiative. Presented at: Radiological Society of North America Scientific Assembly and Annual Meeting; Nov. 25-30, 2012; Chicago.