Oh, what tangled webs we weave.  Actually Craig there is a lot of anecdotal evidence, many experts, and a theory that supports what you said. And in fact this theory was followed by a certain someone when starting to run a couple years ago. Admittedly it says to run at 60% or less for the first 4 - 6 months. I don't think there is any doubt that as your body becomes more efficient with training, you can run faster at a given heart rate. All this  is one reason I rarely use a Heart Rate Monitor.

For what it is worth...I had the cardiac stress test done 3-4 years ago. The doctor commented that my heart was like an 80 year old man, large and slow. I think that was supposed to mean good. While on the treadmill, I never felt stressed at all. I think they took me off too soon.

When running hard my heart rate is around 175. Hrmax = 220-age is obviously wrong for psuedo-athletes like me since 175 is near my 100% rate. Based on the wikipedia quote, I think the study that established the so-called HRmax isn't statistically significant.

http://en.wikipedia.org/wiki/Heart_rate

Haskell and Dr. Samuel Fox.^{[[4]|http://en.wikipedia.org/wiki/Heart_rate#cite_note-mhrt-3]} Inquiry into the history of this formula reveals that it was not developed from original research, but resulted from observation based on data from approximately 11 references consisting of published research or unpublished scientific compilations.^{[[5]|http://en.wikipedia.org/wiki/Heart_rate#cite_note-mhrt2-4]} It gained widespread use through being used by Polar Electro in its heart rate monitors,^{[[4]|http://en.wikipedia.org/wiki/Heart_rate#cite_note-mhrt-3]} which Dr. Haskell has "laughed about",^{[[4]|http://en.wikipedia.org/wiki/Heart_rate#cite_note-mhrt-3]} as it "was never supposed to be an absolute guide to rule people's training."^{[[4]|http://en.wikipedia.org/wiki/Heart_rate#cite_note-mhrt-3]}