jono´s last post was good and interesting. But still my thinking, about the importance of the metabolic system and neuromuscular coordination/running economy TOGETHER, hasn´t changed. As I wrote earlier my thinking is largely based on the qualities of the muscle fibers. By training we can change the balance of the anaerobic and aerobic capacity, and try to reach an optimum balance for the main event. Muscle fiber has contractile AND mitochondrial protein etc. Increase the relative quantity of contractile protein --> you have relatively smaller quantity of mitochondrial protein etc. How good muscle stiffnes and anaerobic capacity you need depends from the main event, if you are 800m runner these are more important than for a longer distance runner, so you have to sacrifice some endurance (aerobic capacity, not speaking ONLY about the VO2max) that could be possible for you to reach, or you won´t be fast enough for the event. You just cannot be at your best for 3-10k etc. if you do the training that 800m demands. So I can say that Lydiard was wrong on this case, because for what I know he basically gave the same schedule (maybe a bit different, but not enough) for every runner from 800m to the marathon. From this you can figure out my answer to the original question of the thread; Does the Lydiard/Wetmore system do enough to develop speed? The answer is no, at least when speaking about the training of an 800m runner. Of course we have to remember that training of all 800m runners etc. isn´t identical, because everyone is different, if you already have the speed but not enough endurance to use it well, then you try to keep it high while improving your endurance, and so on..