I have to disagree with this conclusion. From everything I've read, MHR is simply an individual characteristic, like height or hair color, and has nothing to do with fitness or athletic ability. I think the "formula" is off for the general population as well as for the "active" population. I think studies underestimate MHR because it is hard to reach and takes a lot of exertion. Active people are more likely to put forth the effort to reach max and thus report higher MHRs, but that doesn't mean they really have higher MHRs. This is from the link I earlier cited regarding the problems with the "formula":

"Dr. Haskell culled data from about 10 published studies in which people of different ages had been tested to find their maximum heart rates.

The subjects were never meant to be a representative sample of the population, said Dr. Haskell, who is now a professor of medicine at Stanford. Most were under 55 and some were smokers or had heart disease. . . .

But, exercise physiologists said, these data, like virtually all exercise data, had limitations. They relied on volunteers who most likely were not representative of the general population. "It's whoever came in the door," Dr. Kirkendall said.

In addition, he and others said, gauging maximum heart rates for people who are not used to exercising is often difficult because many prematurely stop the test.

As the treadmill hills get steeper, people who are not used to exercise will notice that their calves are aching. "They will say they can't go any further," Dr. Kirkendall said."