Training & Nutrition - Training with low vs high cadence

Guided by Carmichael's "The Ultimate Ride", I've been putting in lots of foundation, endurance, and tempo miles at a high cadence. Re-reading his description of tempo, though, I noticed that it calls for low cadence so I adjusted my routine and did one hour of tempo and one hour of endurance. They are roughly at the same heart rate, but when I kept my cadence low, I was unable to get my heart rate up to the target zone and my legs felt like they were being pushed to their limit. I mashed as hard as I could for an hour and then switched from tempo to endurance with a high (> 90) cadence. Almost immediately I was able to get my heart rate up to the target zone and my legs were much less stressed.
Last year, my first season back after a long absence, what limited me on long steep hills was my lack of aerobic capacity, i.e. I would run out of breath. This year what is limiting me on those same hills is lack of muscle, i.e. my legs just can't push any harder but I don't run out of breath.
I'd read that high cadence demands more aerobic capacity than low, but I'd never experienced it so directly as I did this afternoon. Obviously, I need to do a lot more tempo riding at low cadence so my legs will come up to the level of my aerobic system.

There was an article by an ex Euro racer in Bicycling mag (whohoo!!) a few years ago that described a hill climbers training technique: after getting an adequate basis,which you have done, find a hill of at least a mile length and 5% or so grade. Do a series of rides in a high enough gear that your cadence is 45-60 range and push it on up that hill. This builds strength and hill climbing conditioning. It is not easy either.
It is not used except as a training method. It can be hard on knees so adjustments may be necessary. People in Florida, Kansas and Okla will have to find a headwind to substitute. Steve

I believe that actual fat burning occurs more readily during the slower cadence as well.

Part of the issue is that V02max can be brought close to maximum with a year of good training. Lactate threshold, which limits most riders, takes years to bring up to optimal values for a given indivdual. You can have a terrifically high VO2max, but if your LT is not up to snuff, you will not be able to utilize it, because your legs will fail you long before you challenge your aerobic system.