[填空题]

Is Running Bad for Your Knees Maybe Not

A. Perhaps because it seems intuitively true, the notion persists that running, especially when done long-term and over long distances, is bad for the joints. Indeed, it would be hard to think otherwise when with each foot strike, a runner’s knee withstands a force equal to eight times his or her body weight—for a 150-1b. person, that’s about 1200 1b. of impact, step after step.
B. The common wisdom is that regular running or vigorous sport-playing during a person’s youth subjects the joints to so much wear and tear that it increases his or her risk of developing osteoarthritis (骨关节炎) later in life. Research has suggested that may be at least partly true: in a study of about 5000 women published in 1999, researchers found that women who actively participated in heavy physical sports in their teenage years or weight-bearing activities in middle age had a