Acute effects of physical exercise on the deformational behavior of articular cartilage and changes in cartilage oligomeric matrix protein (COMP) are definite. However, conclusive positive effects of fitness exercise on functional adaptation of articular cartilage have not been proved.Therefore, in this parallel-group randomized control trial, the investigators tested the hypothesis that adequate amount of physical exercise with enough impact would be able to stimulate the functional behavior of articular cartilage.