For me 75% max heart rate was 20 beats higher than my original MAF value. Indeed, for those with low max heart rates, Maffetone's recommendation can be way too high and at that point, I defer to Hadd's recommendation (Hadd actually accounts for those with high max HRs by chopping off the extra over a certain value). 75% HRR puts me 30 beats higher and in fact, right about my anaerobic threshold at the time I started doing MAF! One should be careful using max heart rate as a metric for anything, unless following Hadd, other than to know if you have a very low max.

Cheevers- Do you use the absolute number for % of Max HR or do you subtract resting and add it back in after you take the percentage?

I use absolute %. If I use the Heart Rate Reserve calculation and make the adjustments Pfitzinger provides in Advanced Marathoning, then the numbers are higher and -- consistent with the LHR philosophy -- I choose the lower number. For example, if I want to run easy I stay below 75%, which for me is 125 bpm (I actually try to stay @120 to be safe). The comparable HRR% for an easy run is 70%, but that puts me at 130. Those five bpm make a difference -- which is why I find that 20 beats per minute difference preposterous. For me, the difference between running at 135 bpm and 155 bpm is like 2 minutes per mile. I understand Jesse's point, but I still think that benchmarking to an arbitrary number is not as good as benchmarking to something specific to my fitness, even if it's still flawed. I can also see how the issue becomes less clearcut the higher your max HR is.