BACKGROUNDAcute effects of physical exercise on the deformational behavior of knee articular cartilage and changes in cartilage volume are definite. However, conclusive effects of different exercises on the loss of articular cartilage volume have not been proved. In this parallel-group randomized controlled trial, we tested whether 12 weeks of swimming, powerstriding, cycling, and running exercises would decrease the cartilage volume significantly and whether there would be a difference in the loss of cartilage volume after different types of exercises.

METHODSFrom October 2012 to January 2013 we evaluated 120 healthy volunteer students in Biomechanics Laboratory of Tongji University. Body mass index (BMI), right lower limb strength, and right knee cartilage magnetic resonance imaging (MRI) were obtained before exercise. MRI were conducted in East Hospital. The study was approved by Tongji University Ethical Committee, all subjects were randomly assigned to the running, powerstriding, cycling, swimming, and control groups by a drawing of lots. Each group contained 24 samples. At the end of 12 weeks of regular exercises, the same measurement procedures were applied. Cartilage volume was calculated with OSIRIS software based on the quantitative-MRI. Pre- and post-exercise comparisons were carried out using paired t-tests and one-way analysis of variance (ANOVA) was used to compare differences of cartilage volume loss between groups with Student-Newman-Keuls procedure for multiple comparisons.

RESULTSRunning, cycling, and swimming groups resulted in a significant decrease in BMI. The quadriceps peak torque increased significantly in the swimming and cycling groups. Total cartilage volume significantly decreased in the running and cycling groups after 12 weeks of training, without any significant change in the nonimpact swimming, low-impact powerstriding, and control groups. Loss of total cartilage volume in the running and cycling groups were 2.21% (3.03) and 1.50% (0.42).

CONCLUSIONSTwelve weeks of regular physical exercises (i.e., running and cycling) decrease the total knee cartilage volume. Swimming and powerstriding are recommended for the healthy youth. This finding suggests that articular cartilage has the functional adaptation for exercises, and some sports could be the risk factors for the initiation of osteoarthritis (OA) in young healthy adults.