First of all, I really did not intend to open the proverbial can of worms with this. My intention was to post those links and then have people make of them what they will. I am not in a position to defend other people's research, although I do think I'm pretty good at sifting through what's out there, given the minimal time I've put into this.
Second, I think you have too strict of a conception of aerobic versus anaerobic running. Sprinting for 100 yards or less is close to purely anaerobic running, anything above that involves both. Ultras would be the opposite extreme, involving close to purely aerobic running. Try to hold your breath for 2 hours and 10 minutes and you'll see that it would be quite impossible to run a marathon purely anaerobically (OK, OK, I realize the brain would suffocate too, but you get my point).
In any case, and third, the question at hand was how to build one's aerobic base. We both know the Maffetone prescription. I was pointing out that that is not, apparently, what pro endurance runners follow, at least not anymore. As we've both pointed out (see my comment above) they use something like a 80/20 or 70/30 or even, lately, a 60/40 ratio of LSD to speedwork (speedwork here defined as basically anything above a LSD pace, and may involve Bilat's 30-30 protocol, traditional intervals, tempo runs, race pace runs, etc.). And note that LSD runs can still be very aerobic at 25-40 beats per minute above the Maf guidelines, that is, at what most of us would perceive as an comfortable level of exertion (i.e., at a nose-breathing, conversational pace). Barefoot running has nothing to do with this (although having no extra weight at the end of the legs is more efficient, this may be counteracted by whatever advantage shoes confer in negotiating surface textures--I think the jury's still out on that one).
Fourth, the ability to run at one's lactate threshold is apparently the best physiological predictor of performance, not heart rate, as indexed by VO2max. So, not surprisingly, pros spend a fair amount of time training at lactate threshold, and don't worry too much about their heart rates. True, they're pros and have learned to read their bodies very well. For beginners, or for those who don't have much of a background in sports, a heart rate monitor might be useful in getting feedback on how much one is exerting oneself. For me, it's completely redundant. I have a pretty good idea of what a sustainable, aerobic pace is for me.
Finally, as for training plans, you might try something like what I've been doing recently: three times a week = one LSD run, one tempo run at about 60% LSD distance, and one intervals and/or hills run. Four times a week, add another LSD run. Five times a week, add a short recovery run after your longest LSD run. Also, I'm thinking of experimenting with paces ('the basics' of running), using a pace calculator. So, for example, if you can run 6 miles at 9 mm pace, you should be able to run one mile at less than 8mm pace. Ok, so try to run six one-mile repeats at 7:30mm pace, with walking breaks in between. Stuff like that. My approach is pretty loose, and this is all pretty new to me, so I'm experimenting, finding what works, but most importantly, finding what I enjoy. I happen to enjoy varied running. The fact that this is what pros do is secondary. A lot of people like running the same routes at the same pace and just zoning out. That's cool too, and that's the way I used to run when I lived in Chicago.
Anyway, if you're interested in this stuff I think a quick search of google or a running site will turn up good material. I didn't have to look too hard. I'll try to post some links but my recreational bookmarks are a mess and I don't think I've bookmarked too many of the things, particularly research articles, as opposed to running sites, that I've come across--it will be just as easy for you to find this stuff yourself. It's all pretty standard now, which is part of the reason I get a little flummoxed (or is it miffed?) when people keep bringing up the Maf stuff over and over again. Quality is winning out over quantity. It's the new religion
. I'm not a racer, and have no immediate plans to race, but I've found it a great relief to learn that (1), you don't have to run long and slow all the time to improve your aerobic base, and (2), running faster does not increase your chance of injury--in fact, the opposite may be true. With this in mind, I thought it was important for others to hear the same news, in case they, like me, enjoy running a bit faster from time to time but thought it was some kind of no-no. That is all. I wasn't trying to tell anyone how to run.
Oh, I guess I should also mention that my initial motivation for increasing my pace was that I became convinced that I run with better form at faster paces, which is part of the reason it's also more enjoyable. I was at 10-10:30 mm pace for longer runs, but felt much smoother at 9mm pace and lower. I can report that one month after incorporating speedwork last spring, I knocked at least 30 secs off my pace (I wasn't using a Garmin at that point, so I'm not sure exactly how much was trimmed), and now again, in September, I knocked off another 30 seconds after returning to speedwork, without really even training that hard! I'm pretty sure I can get down to my goal of 8mm pace or below over an hour's run within another few months with my current regimen. Once I get there, I may back off a bit on the speedwork, who knows?
Go Vikes! Skol!