There have been a few stories out this week with titles such as "Fast running is as deadly as sitting on a couch, scientists find" , "Stop binge jogging" , "Too much jogging 'as bad as none at all'"  after  an article was published in the Journal of the American College Cardiology about the Copenhagen City Heart Study. The study found that light to moderate running was associated with living longer in comparison to being sedentary but running more often/strenuously did not. There were some serious limitations in the study as pointed out in this article about the reactionary press response on the NHS website and that Alex at Sweat Science , who is always worth a read, point out.