> Knee implants Source? I would expect these are much more common in obese people than in habitual runners. My understanding is that runners have been found to

> Knee implants Source? I would expect these are much more common in obese people than in habitual runners. My understanding is that runners have been found to have healthy knees, e.g. with a bit of googling I find [1][2] (but haven't read them). > significant negative hormonal changes for men over 50 miles/wk They have found somewhat lower testosterone levels, but I don't know of any study finding negative health impacts. Do you have a source for "significant negative"? [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5179322/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5179322/ [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556152/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556152/