Ultramarathon runners are not normal people. It's like saying that strength training is bad for you because Ronnie Coleman took a load of steroids and trained

Ultramarathon runners are not normal people. It's like saying that strength training is bad for you because Ronnie Coleman took a load of steroids and trained through a spinal injury. The vast majority of people are never going to exercise even remotely hard enough to cause themselves issues in this way.