I really enjoyed Train Hard, Win Easy, but reading between the lines and watching the Kenyans run, I still think it is mostly genetic. Those long thin legs they have can produce a long smooth stride with very little effort that is something even world class athletes of other races don't ever develop. Spending enough time being around good American runners and then watching Kenyans, it's clear that they'll always be more efficient. The only hope remaining is to try to be much stronger than they are, and that's where they're training comes in. A thin Caucasian runner with the same cardiovascular strength as a Kenyan won't be as fast because it takes them more energy to cover the same distance. Just my opinion, but I've watched a lot of running, trained a lot myself, and read up quite a bit. I can't believe the Ethiopians can beat them.