Yah, although I've only used the HR monitor a friend gave me twice, I do pay attention to my resting heart rate. When I came back from Mozambique I was overweight and out of shape and verging on hypertension--something like 140 plus for the systolic reading. The doc wanted to give me some pills. I said wait, let me try exercising for a few months and see if that doesn't bring it down. I've been close to 120/80 ever since, and my heart rate continues to fall.
Having dabbled a bit with MAF myself, I have concluded that, like Lee, my resting heart rate is almost a better indicator. It may not demonstrate that I'm burning fat more than sugar on any given run, but it definitely indicates how my training is affecting my overall fitness. I monitor my resting heart rate religiously, as soon as I wake in the morning, and have watched a slow and steady decrease when I am training properly. When I start to overdo it, my resting heart rate starts to increase, and if those increases sustain themselves for more than a couple of days, I know I'm overdoing it (or, getting sick, though I don't get sick very often). My resting heart rate when I am in a proper training zone tends to average between 42-44 bpm; if it moves into the 50s, I back off my training a bit, particularly if I'm otherwise feeling healthy.
Every "zone-based" heart rate training system has a fat-burning zone, which is one of the goals of the MAF method: to teach the body to use fat as fuel rather than glucose. And that fat-burning zone is achieved by maintaining a sustained, relatively low heart rate. Nothing particularly unusual about that. Where I and most people tend to get hung up, I think, is trying to reconcile this ultra-slow running method with a converse increase in speed. Anne's point is a good one, I think: over time, it will take increased effort to achieve and remain in the lower zone, as the cardiovascular system gets better conditioned. So, you can push harder (i.e., run faster) at the same relatively low effort.
I mix up MAF runs with non-monitored runs. I know this isn't true MAF-ing, because Dr. Phil's method is pretty specific about base-building and how non-aerobic work can wipe out any MAF gains. But I'm of the view that muscle confusion -- not letting my body predict what's coming on any given day -- is what keeps it stimulated and able to respond to various conditions, because that is what racing presents (unless you always race on indoor tracks). Whether or not I can remain injury-free using this approach remains to be seen. But I think there's a place for MAF, particularly for us newbies whose enthusiasm often trumps our good sense. I just don't tend to want to get religiously zealous about it. Like a minimalist shoe, it's a tool. If it works, I use it, perhaps adapted to the particular job, or I leave it alone.
. I think there were a few toddlers on route who overtook me...
