Running MAF

NOTE: This is an unusually journal-entry-ish post for me. But I think it has some pretty useful concepts. I hope you like it. (Any mention of today refers to Friday, Sept 18, 2015).

For about 2 months now, I’ve been building my aerobic base under the MAF (Maximum Aerobic Function) principle, proposed by Phil Maffetone. I’ve seen an improvement of about 1 minute to my MAF pace—the speed at my aerobic heart rate, which is 148—and yet, I feel like today is the first day I really understood what running MAF is like.

The idea behind MAF training is to lower the intensity at which we train, in order for the aerobic base to kick in with theoretically no anaerobic function. This removes the majority of chemical stress associated which exercise, which comes from the release of hydrogen ions (H+). These ions acidify the body and create an added burden for recovery.

Training under this “aerobic threshold” allows the aerobic base to be developed quickly and efficiently. Typically, 3 to 6 month long period of exclusive MAF training strengthens the aerobic base to the point where it can efficiently absorb the stresses of high-intensity (anaerobic) exercise.

As editor on the MAF website, I answer a lot of difficult questions in the comment sections. For people are first calculating their MAF heart rate, a predictable question always pops up:

“Are you sure that my MAF Heart Rate is 148?” (or whatever). “This can’t be! I’m, like, really athletic. I stuck my first vault at 4 months of age. At two, I was running 5 minute miles. Are you sure it’s not at least 151?”

And honestly, I often feel exactly that way. It’s as if everyone (myself included) is trying to negotiate their way into a higher heart rate—thinking it is the highest possible heart rate (aerobic or otherwise) that will bring the most benefit.

I constantly tell commenters what it has taken until now for me to truly absorb: we have to lower the intensity to maximize the aerobic benefit. Trying to always be right on top of that aerobic threshold—what I’ve decided to call greenlining (as a riff on “redlining”)—is that very same high-intensity mentality, haunting a game that’s all about going low, not high.

Don’t get me wrong: when I run MAF—usually 1 hour, 5 days a week—I scrupulously bookend my workout with 15 minutes of warm-up and cool-down, in which I slowly and steadily bring my heart rate 3 or 4 BPM under my aerobic threshold.

Every warm-up, I notice the same thing: my heart rate oscillates its way up to MAF. It doesn’t climb steadily. Even once I do get close to MAF, it keeps oscillating. It goes up and down some 4 heart beats every 30 seconds or so, meaning that if I want to stay under MAF (which for me is 148) I have to stick with 143.

As a perfectionist, I always try to iron these things out. Maybe it’s fine for the heart rate to oscillate as long as it remains under MAF. But it’s still important to consider what oscillations mean. It means that metabolic work (and my speed) is rising and falling continually, when in theory we want to stay at the same metabolic output.

Maybe I’m overthinking this far and away, but to me this seems like a car lurching down the highway when a few tweaks to the engine would be all that’s needed to create a smoother ride.

Almost by accident, that is exactly what i did. It had been an uncharacteristically bad run: I went out after an hour of having eaten, and I just didn’t want to take my heart rate up there. I did my warm-up, and then dropped back down to 20 under MAF. I just felt like jogging.

As the minutes passed, my heart rate—and my speed—slowly began to increase, at a rate of about one beat per minute. And like that, over the next 20 minutes, I slowly approached MAF. My heart rate came to within 1 BPM, and for the next 40-45 minutes, held constant.

Today’s run was exceptional: I had far better joint stacking. It was extremely easy to keep my breathing in sync with my steps—three steps to an exhale and two to an inhale—and my breathing was also deeper than usual. The experience of running was one of incredibly little stress. When I did get up to MAF speed, I was faster by a full 15 seconds per mile.

And two hours after the run, I was full of energy, and my leg muscles, instead of feeling empty, felt warm and fuzzy. I’m not kidding.

But this makes perfect sense to me: calibration, not raw power, is the primary source of performance. Think of a 1000-horsepower engine with a timing belt that’s just a tiny bit loose. It can’t express a bit of that power. Think of that same engine attached to a gear box with all the wrong ratios, or mounted on a car whose tires are too pressurized. When that engine expresses all of its power, that car is going sideways.

Too often, as athletes and fitness enthusiasts we try to add horsepower when we should be checking the timing belt, or changing the stiffness of our valve springs. I think that in today’s workout—which feels like the highest-quality workout of my life—I enabled my body to focus on the small stuff . . . and get it right.

I’m willing to bet that this very long, very easy warm-up, which “sacrificed” time spent training at a higher intensity, was a central part of it. And I expect my bet to pay dividends in speed.

UPDATE: On Saturday I had an even more protracted warm-up. My speed increased by yet another 20 sec/mile.

3 thoughts on “Running MAF”

  1. Hi Ivan, I’m dzaki from Indonesia.
    I wonder to know why in my warming up run (3 km) with MAF153 BMP my pace always hit faster.
    then after 4 km it will return to constant pace as in my MAF method ?
    I’m 27 years old and fit into category d, so I add 5 BMP for MAF.


  2. Hi Ivan, I’m from the UK.
    I have just started back in the gym for exercise that is not so weather dependent.
    I do walking, cycling on IC7 bike and rowing on Concept 2. My MAF is 115 and I find that it takes about 30 mins to steady my heart rate on the treadmill. So, I now use a 30min warmup to 3-5 beats below MAF.
    This is in contrast to most of my exercise in my previous life – there a warm-up meant getting your heart rate to the 160s+ :).

    Loving your site and the MAF site. I hope soon I will be able to complete a Parkrun at a running gait (at MAF)!

    Background – I have been doing Pilates with a great instructor, twice a week, for the last year and posture, mobility and shoulder stability have improved and some mobility issues and injuries have disappeared – in the beginning, I couldn’t lift my left arm above hip height without pain and I had extremely short quads from an serious ankle injury that resulted in my glutes being inactive for many years – these took a long time to activate before strengthening could happen. I am still 6 stone overweight but it is coming down on a lower carb diet (think Zone).


  3. Hi Ivan. Thank you for this great website, the content is fascinating.

    I’ve been training MAF for a while now as well and reached a similar breakthrough today after reading this post a few days back. I realised that my MAF number (152 – 28 years old, been doing almost nothing but anaerobic training for about 8 years in the weights room, healthy and infrequently sick but broke a metatarsal playing five a side soccer last year) was inaccurate as I didn’t account for the fact that I get hayfever!

    Having brought the target HR down to 147 and slowing down the pace at which I ease into a run, I managed to run one of the 10 kilometres I ran at 5:08 with an average HR of 144 in horrible weather (windy, wind chill making it feel like -3 deg C, hail falling at points, and very dry air). Previously I’d been only able to hit that pace in good conditions with a heart rate averaging 150.

    I also found that it was easier to control any drift in heart rate with my breathing and stride length, and that now my respiratory muscles are stronger I was able to maintain a great breathing pattern with my strides – something I’d struggled with before. I’m staggered at myself, especially considering the same pace run at a similar pace in better conditions only a week ago would necessitate an average heart rate that was 7-10 bpm higher!

    There’s a lot to be said for checking the ego even further than the formula might suggest. I wonder how much of this improvement I can attribute to the longer warm up, better breathing and cadence or simply reducing the target heart rate. Are seasonal allergies really such an important factor in the MAF heart rate?

    Thanks again for your work – the comments on the Phil Maffetone website you leave are as insightful as the articles on here!


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