Category Archives: MAF



Whatever your sport and whatever the distance, pacing is the key to success. Unfortunately, it is the thing people have the greatest difficulty with in training and racing.

I swim with a masters group. Somedays I swim with the fast crowd and other days I go to a more low key session. In the low key session I swim with a man that is super competitive. Competitive in the sense that he doesn’t want to be the slowest or not be able to keep up – not competitive in that he is the fastest swimmer. So if he is in the lane next to me he will kill himself going all out to keep up and last maybe 25-50 meters then has to slow way down. He bemoans to me all the time, “I don’t know how you can go so fast, I can’t keep up.” I tell him continually, pace yourself. Only go as fast a pace as you know you can hold for the entire set. In his case, when we recently swam 10×50 meters on a minute, he completed about 50% of the set because he had to sit out every other 50 because he was so winded from the previous one. The next time we swam, I paced him. I swam a pace I figured he could hold and he was able to do all 10 50’s. He finished them all. Tired but not sucking wind and exhausted.

In marathon racing, people start off feeling good and strong but usually start way too fast and have to slow to a crawl the last 6 miles or so.
Had they started conservatively they wouldn’t have had to have slowed down as much,  if at all,  and would have run faster over all. Every world record in running has been made negative or even splitting a race – meaning the second half was run at the same pace as the first half or faster.

With all the excitement of being fast or meeting our goal, we tend to just go hard from the get go and try to hang on to that pace. And some people can hang on for a long while! I was running a marathon and passed a woman at about mile 8.  As I passed, she latched onto with me and we ran together for about 8 miles with her at my heels. All I remember was listening to her labored breathing. She was breathing hard, and I couldn’t believe she had the mental toughness to hang onto a pace that was as hard for her as her breathing indicated. I actually thought maybe she could hang on but she did finally slow way down after those 8 miles together.

Pacing in sports is about understanding and building your energy systems that are specific to your distance and to the goal.
You can go hard but hard is relative to the distance and your training. On the most basic level we have two energy systems —  the aerobic system and the anaerobic system. The aerobic system uses oxygen to create energy and prioritizes fats as a source of fuel. The anaerobic system doesn’t use oxygen to create energy and prioritizes glucose as a fuel source. When the body relies on the anaerobic system to create energy from glucose the by-product is lactic acid. If you create more lactic acid than your body can clear you will have slow down. Aerobic and anaerobic systems work concurrently. As you are running or exercising it is not which energy system is working, but which predominates.

No matter the work we are doing, our body burns fat and/or glucose for fuel.
If you are sitting around watching a movie or sleeping for example, you are burning mostly fat as the fuel. However, if you start to move and put demands on your energy systems, and depending on your level of fitness, your body will at some point start to use a higher percentage of glucose for fuel and less fat. This too, is a sliding scale much like the aerobic and anaerobic systems.

Lets say, for example, I go out for a jog and I am at a pace that I can talk to my running partner without much effort, I might be burning 80% fatty acids and 20% glucose. I am prioritizing my aerobic system. But lets say we up the pace a bit. I can still talk but only a couple of words at a time before needing to focus on breathing. I might  now be burning closer to 50/50.  If I continue pushing the time spent at that level,  I will start prioritizing glucose as the main source to fuel – it is a quicker form of energy for our bodies to access. We push faster still and now I will be 80% glucose and 20% fat. I am now predominantly using my anaerobic system to produce energy. Depending on how efficient my body is or my running partner’s body is, we will switch from burning  predominantly fat  to predominantly glucose at different paces. In other words, each of our aerobic energy systems will switch to the anaerobic system at a different pace depending on our body’s ability to keep burning fat as fuel and utilize oxygen. Being able to stay aerobic for a long time at a high effort is what we call someone’s aerobic base – and for endurance sports you want a big aerobic base.

In the example from my marathon race, I was breathing comfortably at the pace we were running together and the other woman was huffing and puffing. She was working more of her anaerobic system than I was.  Since I was aerobic at that pace my body was able to burn fat as the main fuel and I was able to keep lactic acid build up from happening — I didn’t need to slowdown or refuel. The other woman, in a mostly anaerobic state, was getting a lactic acid build up since she was burning glucose as fuel, which forced her to slow her pace. Here’s the thing – your body (even the skinniest body) has enough fat to burn as fuel for hours and hours – tens of thousands of calories stored as fat but the body can only store about 2,000 calories of energy in the form of glucose in the muscle and liver. That’s about 1.5 to 2 hours worth of fuel. When you rely on glucose to fuel your exercise and you run out, you bonk.

As you train you want to become comfortable using different amounts of both the systems.
You should know what it feels like to go for a long time aerobically as well as how it feels to go anaerobic and how it feels like to be somewhere in the middle. My friend in the pool needs to work on a pace that would have him in a more aerobic zone – even though its a short distance. As he pushes the envelope at the edge of his low anaerobic zone without going purely anaerobically. Then he will be able to swim 10×50 meters without having to stop from exhaustion. The woman behind me in the marathon would have finished the race in a faster time over all by not speeding up with me and staying in her aerobic zone. The consequences of going anaerobic will cause drastic decrease in time even though part of the race was run faster.


How do you train to fix it?

There are lots of formulas out there but I’ll make it simple and as you gain experience you can study the variety of way in more detail or other peoples plans and formulas – though the basics are all the same. Phil Maffatone developed the MAF (maximal aerobic function) method and lots of people have found it to be a great way to get faster. Famed triathlete, Mark Allen, used it to become an Ironman World Champion and holds the record for the fastest marathon for the Kona race. Building an aerobic base takes time and patience but if you give it the time you will be stronger aerobically and not burn out chasing a pace by over taxing your anaerobic system.

Here is the way to calculate the heart rate you should train at (your MAF heart rate) to build your aerobic systerm – (the following is taken from Phil Maffetone’s site –


To find your maximum aerobic training heart rate, there are two important steps. First, subtract your age from 180. Next, find the best category for your present state of fitness and health, and make the appropriate adjustments:

  1. Subtract your age from 180.
  2. Modify this number by selecting among the following categories the one that best matches your fitness and health profile:
  3. If you have or are recovering from a major illness (heart disease, any operation or hospital stay, etc.) or are on any regular medication, subtract an additional 10.
  4. If you are injured, have regressed in training or competition, get more than two colds or bouts of flu per year, have allergies or asthma, or if you have been inconsistent or are just getting back into training, subtract an additional 5.
  5. If you have been training consistently (at least four times weekly) for up to two years without any of the problems just mentioned, keep the number (180–age) the same.
  6. If you have been training for more than two years without any of the problems listed above, and have made progress in competition without injury, add 5.

    Once a maximum aerobic heart rate is found, a training range from this heart rate to 10 beats below could be used as a training range. For example, if an athlete’s maximum aerobic heart rate is determined to be 155, that person’s aerobic training zone would be 145 to 155 bpm. However, the more training at 155, the quicker an optimal aerobic base will be developed.


Now you should have a MAF HR zone. First test yourself. Go for a run of 3 miles or a route of about that length that you can use each time you test. If you are new to running and 3 miles would be too long, you can make it shorter. The idea being that you want a route that you can run and repeat the test when needed. It should be as flat as possible. Warm up well – 10-20 min. Then start the run and stay in that zone you figured out. Note the time it took you to finish and keep a log of it.

Now follow your training plan and stay in that MAF zone. Sometimes you will have to walk to stay in your zone – that’s OK. Even experienced runners will find they may have to walk. Re-test every two weeks. You will see your “MAF pace” drop – the time it takes for you to complete your test will improve. Some runners will get to the point that their running pace at their MAF HR gets so fast that it becomes hard to maintain! When you get a big aerobic base from your MAF training (you can build an aerobic base for years!) you can start incorporating other forms of training with different paces and thresholds. But a big base of aerobic work is the foundation of endurance sports. Don’t neglect it!