Very interesting bret. His marathon improvements are simply astonishing. I would like to add aome anecdotal findings to this that i just came across personally. You both know i have not been running, but at the begining of this semesterni took part in an acsm fitness test. Basically do a vo2max test via a one mile walk, muscular endurance for upper body via max pushups, a curl up test for abdominal endurance (modified sit up), and the back saver sit and reach to test flexibility. My training kept me in fair shape though, went from 36 to 33 pushups after not having done any in two months, curl up teat went up by 2, (forgot about bmi, bmi stayed the same and is not useful or applicable to someone of my size and weight, aka I’m too damn strong!). But the really big change was my 1 mile walk test, my vo2 max went up 2 points! That is kind of significant imo since a lot of vo2max is your god given genetics. I will say that the first test was me walking by myself around a neighborhood, and this one was a high energy race with me being motivated to walk faster. However, i think it’s worth noting.