I’ve been a runner for decades, fully aware that the pounding was probably destroying my knees. A recent article in the Times says that to the contrary, this longtime conventional wisdom is wrong. Studies have found runners’ knees are stronger than those of non-runners, and less susceptible to injury. The same issue of the Times had an article saying that – contrary to previous assumptions – weight training was good for the arms of those who’d had mastectomies, not bad for them. This reminded me of all the years we were told that eggs were poison, until we were told maybe they weren’t so bad after all. Eat them in good conscience. Same thing with butter. Don’t eat it, we were warned. Eat margarine instead. Except margarine turns out to have far more saturated fat. Back to butter. Moral: avoid rigid warnings about what to do or not do based on studies that are subject to new studies.