They are true statements. How is what possible? There is no meaningful way to measure that. I'm sure it has something to do with the fact that the magnitude of stress reaches a point where resources are competed for at a greater extent. If you are looking for an explanation on the molecular level it is doubtful that we will ever get one, even from scientific journalists because no one will ever fund a study to look at that. Getting jacked guys more jacked is not a public health concern even if it is for us.