Dear Mark: Maximum Aerobic Function (MAF) Training

maximum aerobic functionFor today’s edition of Dear Mark, I’m going to be answering questions about Maximum Aerobic Function, or MAF. If this is your first time hearing the term, MAF refers to a method of endurance training that maximizes the function of your fat-burning aerobic system. I’ve come down hard on conventional or popular modes of endurance training in the past for being too stressful and reliant on sugar. MAF training is the opposite: low stress and reliance on body fat.

Let’s dive right in to the questions:

What is MAF training?

MAF trains your aerobic fat-burning system to be more efficient and produce greater output at the same “intensity.” It means slowing the hell down to go faster. It means the slower you go, the more fat you’re burning and the better your mitochondria are getting at utilizing fat for energy. It means training up to but not over your maximum aerobic heart rate.

MAF was coined by Phil Maffetone, who came up with an ingenious way to calculate your max aerobic heart rate: subtracting your age from 180. 180 minus your age gives you the heart rate at which you’re burning the maximum amount of fat and minimum amount of sugar.

Say you’re 30 years old. 180 minus 30 is 150. To burn the most fat possible, you maintain a heart rate equal to or lower than 150 BPM. Now, and here’s the trick: It doesn’t sound like much. It doesn’t feel like much. It probably feels way too easy. But bear with me. It works. This is where the magic happens, where you accumulate easy volume, where the “base” is built, where you begin building more fat-burning mitochondria.

The hard truth is that if jogging spikes your heart rate past your aerobic max, you’re not very good at burning fat during exercise. Even if you don’t “mind” pushing that heart rate up. Even if you “feel fine” jogging at 153 bpm. 180 minus age is where you have to be to improve fat burning. That might look like jogging, or walking, or walking uphill, or running pretty briskly, depending on where you’re starting. It’s all relative to your aerobic fitness.

It takes patience to stay at the aerobic zone, but over time, if you’re consistent, you’ll notice that you can handle a higher and higher workload at that same “easy” MAF heart rate. You’ll be going faster while still burning mostly fat—and it’ll still feel easy.

What are the benefits of cardio using MAF training?

In some parts, I’m known as the anti-cardio guy. I coined the phrase “chronic cardio,” and the entire reason I got into this Primal business is that decades of elite endurance training—marathons and triathlons—wrecked my body and drove me to develop and pursue a different, more sustainable path to health and fitness.

But I’m not anti-cardio. In fact, moving frequently at a slow pace in all its incarnations forms the foundation of my Primal Blueprint Fitness philosophy. And MAF is just about the best way to do it.

When you build your aerobic base, you don’t just get better at running (or cycling, or rowing, or swimming, or whatever it is that you’re doing). There are more benefits that aren’t as overtly noticeable:

  • You get better at utilizing the fat you eat and the fat you store, paying huge dividends in other areas of your life.
  • You get steadier energy levels throughout the day. There’s always that big bolus of energy hanging around, ready to be consumed and converted into ATP. And you’re very good at burning it.
  • You have a lower propensity to snack. It’s easier to stick to a healthy way of eating and refrain from snacking when you can cruise along eating your own adipose tissue in between meals.
  • You have more mitochondria, and the mitochondria you have are better at burning fat.1 This is what everything comes down to. Mitochondrial dysfunction and subsequent energy overload lie at the root of many degenerative diseases. The better your mitochondria work, the more energy you can handle, and the less likely you are to suffer the negative ramifications of chronic energy overload.

This seems to confer benefits to longevity. Although we can’t establish causation, moderate exercise—jogging up to 20 miles a week at an 11 minute mile pace—offered the most protection against early mortality in one study. Running more than 20 miles a week, or running at a 7 minute mile pace, offered fewer mortality benefits.2

Plus, having that large aerobic base helps with any physical pursuit, and not just endurance sports. A large aerobic base helps in CrossFit. A large aerobic base helps in football or martial arts or rock climbing. Whenever you can burn more fat, save more glycogen, and still get the same amount of performance, you’re winning.

When you’re aiming for MAF, how much cardio is too much?

As long as you stay in the MAF zone, it’s very hard to overdo cardio. You’re deriving your energy primarily (90/95%) from fat, a virtually inexhaustible energy source, and very little from carbohydrate. You have thousands of calories at your disposal. Your relative intensity is lower than the person who’s out there burning sugar, so your joints aren’t falling apart and your muscles aren’t getting as fatigued. You’re accumulating less stress overall.

When you start hitting intensities that elevate your heart rate beyond the 180 minus age MAF zone, your tally begins. The stress and joint damage begins to accumulate. You become more reliant on sugar compared to fat. You can still train like this, but your margin for error is a lot smaller.

If I had to put a number to it, I’d say that you shouldn’t burn more than 4000 calories a week from cardio.

How should you eat while doing maximum aerobic function?

MAF is most effective when paired with carbohydrate restriction. It doesn’t have to be keto reset levels, although that’s a great option. Standard Primal low-carb, staying under 150 grams per day, is good enough.

When you combine MAF training with carb restriction, everything is enhanced. You build more mitochondria after a single carb-restricted MAF training session than after the same session without the carb restriction. 3

Going low-carb while MAF training also continues the work when you’re at rest. If you burn primarily fat when endurance training but go home to a high-carb diet, you’re squandering a lot of progress.

What if I’m too slow?

One of the most common questions I receive comes from people worried they’re too slow. “I feel like I am going too slow. I can run a 7:00 minute mile no problem at race pace and a higher heart rate, but if I stay at 180 minus age, I can’t get my speed past 10 minute miles.”

You can keep doing the higher HR runs, but you’re not building a base and you may be setting yourself up for damage down the line. That means you are good at burning glucose/glycogen and have a good tolerance for discomfort, but it also means that in this current configuration, you suck at burning fat. The whole point of MAF training is to train at the highest heart rate you can handle (and highest speed) while still getting 90-95% of your energy from fat. Over time, you’ll find that as you get better fat adapted, your mile pace will come down at that same MAF heart rate. That’s the indicator that you are becoming more efficient with your burning of fat over glucose.

Track things over months, not workouts. It may take a long time to improve, but improve you will. Pro tip: if you are a well-trained runner or cyclist, you could probably add 5 to that 180-age number and be OK.

Isn’t my MAF pace way too easy?

It seems way too easy, and that’s the whole point. It’s also where people get tripped up.

You think you can handle a bit more, so you push the HR up. I mean, running at an easy pace couldn’t possibly make you faster.

Over time, you’ll find that as you get better fat adapted, your mile pace will come down at that same MAF heart rate. That’s the indicator that you are becoming more efficient with your burning of fat over glucose.

Just be sure you are always able to carry on a conversation and not get winded as the “guard-rail.”

Folks, that’s MAF training. If you want more details and a specific plan of attack, check out my book Primal Endurance.

If you have any more questions, ask down below! Thanks for reading, everyone.

TAGS:  fitness

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

If you'd like to add an avatar to all of your comments click here!

31 thoughts on “Dear Mark: Maximum Aerobic Function (MAF) Training”

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. Maffetone also recommends that if you have not been a consistent exerciser the last 2 years then you should lower your target heart rate by 10. I’ve been doing MAF for the last 10 months. It’s a bit of a stretch at times to keep below your target heart rate when you are walking/running up an inclined path and not have to slow down to almost baby steps to keep your heart rate down. How hot it is out can also raise your heart rate. I just do the best one can under those circumstances.

  2. In order to do MAF training I guess one would need a heart rate monitor? Any suggestions on a good one? I am more interested in getting in shape and just being able to go out and do things without feeling like I’m getting winded. I am not trying to become a high performing athlete, so I’m most interested in an inexpensive monitor as long as it is accurate.

    1. Matt, I have a Polar H10 heart rate monitor that I really like. It’s relatively inexpensive and it’s easy to pair with your phone.

  3. I’ve been eating primal/keto zone/paleo for 6-7 years now. I love this philosophy, and I’ve been abiding by the MAF heart-rate rule in whatever cardio I’m doing. I can push pretty hard and stay below 180-my age (which does make sense because I feel quite fat-adapted – fasting is easy, I rarely eat breakfast, etc), but it’s past the point of nose-breathing or easy conversation breathing. Is this NLS or is it an indication that I’m burning sugar? I don’t have sugar cravings or anything after I exercise, and my energy is pretty good. I’ve never heard you address this specifically, and I’m wondering what you think it means.

  4. I feel like Mark almost never refers to his career as a triathlete. I like it! Once or twice a year is probably enough, but it kind of grounds the blog.

  5. One question I haven’t seen addressed since I started looking into MAF very recently: should I be shooting to keep my heart rate as close as possible to my target rate, or am I getting benefits at substantially lower rates as well? I’ve been walking with my husband who is 13 years older than I am; will I benefit from hitting his target rate instead of mine?

    1. It is a good question and the answer is yes, you are getting significant benefits from exercising at a HR lower than 180-age. That formula gives you an upper limit, beyond which you begin to interfere with the process of becoming fat adapted. Exercising across the spectrum from far below and up to 180-age is a very healthy approach. As Mark and Brad have said many times, “inconsistency is key”.

  6. Thanks for covering this topic Mark. I read Dr. Ron’s article about this subject but haven’t started working on it yet. Is this method (180-age) different for younger folks? Should I aim for a lower number because my number is so high (157)? I have been wanting to improve my aerobic capacity for a while now but have gotten so lazy (or exhausted from taking care of small children) and re-addicted to video games.

  7. Dumb question, but is measuring your heart rate as simple as counting beats for six seconds and multiplying by 10? Thanks.

    1. Ideally, you should be using a heart rate monitor as you won’t be able to manually measure your heart rate while working out. If you do want to do it manually, check your pulse for 15 seconds and multiply it by 4.

    2. Yep, that’s what I do, count beats for six seconds, then add a zero to the result.
      Not 100% accurate to every beat, but close enough and cheaper than a heart rate monitor, IMHO.

      1. HRM is much better, both for checking your resting pulse and just about essential to keep check when exercising. The shorter time you check it for, the less account is taken of heart rate variability.

  8. I’m a little confused now. I am trying to build up my fitness level to be able to handle long day hikes up small mountains at enough speed to avoid overnight backpacking on all but the longest trips. Think like 15-18 miles in a day with 4000’ of elevation gain and loss.
    I don’t have any problems going that distance on flatter terrain and maintaining 2 to 2.5 mph, but when I hit a steep uphill common to where I’m going, about 1000’ per mile, I slow to a crawl, about .7 mph. I need to get faster on uphills.
    I thought I needed to do more cardio to build my “engine” and improve my VO2max, so I’ve been pushing myself to go faster and get my heart rate up. Now I’m not so sure this is right. How do I know if I need cardio to build my oxygen utilization or MAF to build my fat burning ability? How do I train if I need both?

    1. Awesome point, Rambler. I think hiking up hill is much more akin to lifting weights than it is to the MAF training, and you might be better off combining some kind of weighted step-ups with your cardio. The step-ups could be anything from holding specific equipment on your back at the gym and using plyo boxes to just picking up two heavy things in your house and walking up and down the stairs a bunch of times.

    2. Under the MAF and Primal Endurance approaches, the 180-age limit is used (strictly) for a period of 4-8+ weeks at the beginning of a training cycle to allow you to become more efficient at burning fat as fuel (fat-adapted), build mitochondrial density and ultimately your aerobic fitness. Once you’ve completed this base building phase and assuming you’ve been making steady progress with your MAF testing, then you may enter a shorter 3-4 week process that includes higher intensity work such as intervals, speed work, hill repeats, and additional strength work. This period coincides with the timing of your race, event, or other goals. You then repeat similar mini-cycles throughout the season/year. The Primal Endurance book covers this in detail. Best of luck!

      1. Ahhhhh, that makes sense. Thanks for the tip. I’m doing my first mountain of the season next weekend, so when I get back I’ll try a cycle like this before the next one and see how it affects my speed. I’m all for those N=1 experiments. 🙂

  9. Can’t wait till I’m 130 years old. Max aerobic heart rate will roughly equal resting heart rate so I can finally burn maximum fat in my Barcalounger.

  10. I’m curious how MAF jives with a weekly sprinting session. I’m not a fast runner anyway so I bet my normal runs are under my max (I’ll start paying attention to HR and find out) but I also love finishing a weekly run with a series of sprints. Curious how it all fits together.

    1. If your goal is to develop maximum aerobic function then you should stick with 180-age for all of your workouts for a period of 4-6 weeks. Even short periods of higher intensity work can throw your body into a sugar burning cycle for a couple of days. Once you’ve completed your base cycle, you can introduce sprints and other high-intensity work for a period of 3-4 weeks. This may align with races or goal events, or simply be a time where you reduce volume and dial-up the speed. If your goal isn’t to maximize your aerobic function, i.e. you just want to be fit and healthy, then sprinting every 7-10 days is fantastic. I hope this helps!

      1. So could one not do any weightlifting for said 4-6 weeks? Or would Grease The Groove/microworkouts be fine since they’re so brief (1-2 reps)?

        1. Mark has said recently that micro workouts and lower intensity strength training is fine, but to avoid explosive workouts. Maffetone himself recommends avoiding strength training completely during this time, but I’ve had good results following Mark’s advice.

  11. Nice to see this as I’ve been wanting to hear Mark’s take. My question is, how does sprinting and HIIT fit with this? Once a week ok to push beyond the usual 180-age max?

  12. The first time I tried MAF training, I was frustrated by how slowly I had to go and felt like I could never get in a rhythm running that slowly.

    My wife decided to train for a half-marathon, and she really liked a program where they had her alternate running and walking, and I went along with her. I started tracking heartrate with this training and found that I would get up to about 140 with the jogging (I’m just over 40), then the walking would bring it down and I could cycle like that. Can you comment on alternating running and walking to stay below the target heartrate? Good alternative? Suboptimal compared to a pace that maintains just below the threshold?

  13. I have a question I can’t seem to find a conclusive answer to ANYWHERE: I am in my aerobic base building period, but I have a regular Hatha Yoga practice. Does Hatha Yoga (holding postures for anywhere from 10-15″ to 60″ depending, with slow movement to and from poses) interfere with aerobic base building since it is technically bodyweight strength training? The style I practice includes a hefty yoga nidra (deep relaxation) and pranayama (breathing practices) as well, so there is def some parasympathetic activation during the practice. If you can answer this, I will be SO grateful! A quick background: I have been fat adapted for a few years now, but because I wasn’t using HR/MAF training until a few months ago and was running marathons, was majorly overtrained and experiencing all kinds of terrible hormonal /HPA symptoms like amenorrhea, mood swings, chronic fatigue and sleep interruptions. I have been nursing myself back to health for a few months, and felt like yoga was really helping, but Maffetone is pretty clear about ZERO anaerobic/strength training. I am just looking for some clarity/guidance. I want to continue both practices, but not to the detriment of either. THANK YOU!!

    1. I’m no expert on MAF by a long shot, but have been a part of several MAF forums for the past couple years, and can tell you the consensus on this would be that If the postures you’re holding put you over MAF, it’s interfering w/ your base-building.

      There’s always a few dissidents hanging around in any given group, but the majority of MAF vets preach a pretty hardline gospel.

  14. My aerobic training is weight training. Due to some spinal issues, I am unable to run but can walk long distances, but I am unable to get my heartrate anywhere near the 180-age recommendation when walking. I participate in modified Crossfit classes 4 times per week. Could I use the MAF training principles and still get similar benefits?