I just had an epiphany.
[Sorry if this is long-winded and dull.]
I was thinking about how every coach means something slightly different when they say "threshold run" or "tempo run," when I started thinking about how Jack Daniels' thoughts on VO2max interval training is so radically different from my own experience. He advocates running 3-5 minutes at one's maximal heart rate, but I can only attain that maximum for a second or two. Then I started thinking about some other things that have never added up... and now I get it!
For one thing, Daniels talks about how there's a specific pace that's related to VO2max. In my experience, as I run at any constant pace, the effort level increases until I hit a collapse point and, if I run at a steady heart rate, my pace drops precipitously. This is related to what Brad Hudson calls the "VO2max slow component" (page 52 in his book). What has always been unfathomable to me is that there are people who run a marathon at constant pace and constant heart rate at the same time; it just doesn't work that way for me. While the effort level increases for them, it is not reflected in their heart rate, though for me the two have been synonymous... I assume that what holds true for me holds true for others, which is the same error that all the others have made, just from the opposite view.
What Daniels says holds true IF one's heart rate is the limiting factor in one's VO2max. For me, it's not. I'm running very anaerobically for several minutes before my heart rate drifts up to maximum. I can (and have) run a half-marathon at 95% maximum heart rate, which is supposed to be impossible. This is because my body isn't limited by heart rate, so it shoots up quickly because it can and I've trained it to do that.
The big question then is: if my heart rate isn't limiting my VO2max, what is? Certainly something is holding me back. Let's take a look at all the components that make up VO2max, one by one. First is heart rate, which we've eliminated. Second is stroke volume, which is inversely correlated to resting heart rate; mine is currently 38 bpm (though just standing before a run, it's often 70-85, again because my heart rate's the first thing to shift), so that's not it. Next is vital lung capacity; though my lungs are scarred from recent recurrent infections, mine's about 5.5 liters, which is okay. Next is peak respiratory flow; I've had allergic asthma problems, but I'm currently slightly above average there too. Next is capillarization of muscles, which after 30 plus years of aerobic training, is certainly not the problem, nor is blood vessel diameter - I have some pretty ropy veins. I'll assume that there isn't a 2,3-bisphoglycerate problem, or some other rare genetic flaw (like a thallesemia). I eliminated blood pressure and viscosity issues, though chronic dehydration causes me to have some odd readings.
This leaves the blood itself. And here's where things get odd. I recently had a blood test that showed me to be anemic. My first thought was that it was like when Dr. Gabe Mirkin found the entire US women's Olympic track team was testing anemic; that it was just a flaw of the test (he decided that, as athletes have larger blood volumes, it was a dilutional phenomenon). Further investigation came up with:
1) Heavy training was causing steady small blood losses in urine.
2) Impact shock from long hard running was causing "march anemia," first noted in soldiers in the 1880's. The repeated landing shock was causing blood cells to rupture in the feet.
3) My dietary sources of iron are all chelated. For example, spinach is heavy in iron, but it's bound by oxalic acid. Phytic acid (found in nuts, legumes and grains) is another chelator. Then, given the amount of tea and coffee I drink, tannins decrease iron absorptivity. On paper, my diet is rich in iron, but I'm not getting any of it!
Maybe I can change things with diet and better recovery. Even if I can't, at least I know that it's pointless for me to try to follow any training plans designed for someone whose body reacts differently from mine.