This is way too complicated:))) Love fellow runners but this was a bit overwhelming. The more I run the more I realize that it's not that complicated. I'm currently training for a 2.40-2.45 marathon (a race three weeks from now and another one in Dec). I already ran a 2.49 and 2.46 over the last year. I'm 43; all of the improvement happened in the last 2.5 years. I think it comes down to doing mileage and doing 3-4 different types of runs. Also running "to feel" has been my major improvement