Abstract running man form lines and triangles point connecting network on blue background

Zone 2 Training: Playing the Long Game for Lasting Benefits

What does it reveal about most of us when one of the greatest endurance athletes of all time struggled to run an eleven minute mile?

Dr. Maffetone told me my problem was due to adrenal stress caused by too much “anaerobic” training. At first I was skeptical, but Dr. Maffetone had me go to the nearest track and run a mile with a heart-rate monitor set to my aerobic threshold. I was shocked to see that I could not run a mile under eleven minutes aerobically: this was unbelievable given the fact that twelve months prior I had run over twenty-six miles consecutively at an average pace per mile of 5:48!

Mark Allen went on to become a six-time winner of the Ironman World Championship, beginning with what might be the most iconic endurance race in history—the 1989 “Iron War” in which he dethroned six time champion Dave Scott with a blistering 2:40 marathon.

That pace held the record for 27 years—arguably longer, given that it included the bike-to-run transition. Racing side-by-side, the run opened with a brutal climb and steep descent that within two miles had completely toasted their quads. Then, as Mark describes:

“…someone bolted out of the crowd of thousands cheering us on. It was Dave’s wife, Anna. She held out their newborn son Ryan so that Dave could see him. And she didn’t just stand there. She started running alongside us. Yes, Anna with baby outstretched, was putting down a sub 6-minute mile!

That truly was no ordinary race. Standing alone as a 5k, those first three miles—just 2% of the overall race distance, would be enough to wreck most of us.

But the real wreckage nearly happened well before race day. In the early part of his career, Mark “was always feeling one run away from being too burned out to want to continue my training.”

Enter Zone 2 Training

Zone 2 training focuses on training at a heart rate that primarily engages the fat-metabolizing slow-twitch muscle fibers. That exertion level increases the density of cellular mitochondria—literally, the powerhouses of the cell, while simultaneously optimizing the MCT-1 transport mechanism that clears lactate by sending it back to the mitochondria, where it is reused for energy.

We’ll go into the science of all that next week. Let’s begin with an overview of what this type of training is like. It has been described as “training slow to race fast” and despite people’s understanding of how slow that might be, the pace is invariably and universally met with resistance.

Cartoon with two runners behind a turtle with the caption: I think we should pick up the pace. That turtle just passed us.

In a study of 229 experienced 5k and 10k runners who exclusively did aerobic based training for five months:

  • Every one of them complained about the slowness of the pace
  • At the end of the period, 77% ran a personal best

Speaking of slow, what was the deal with that eleven-plus minute mile pace that greeted Mark Allen’s first assessment? It happened when he embraced Phil Maffetone’s approach, who coached him to keep his heart rate at or below 155 bpm, based on the simple formula:

Maximum Aerobic Function (MAF) = 180 minus Your Age

Mark described his progression after he initiated Zone 2 training, including his drops in time over the subsequent twelve months:

  • Because the pace for the 10k portion of triathlons was close to 5 minute miles, Mark had been training at that pace for at least one mile during every training run.
  • The MAF formula required Mark to slow his pace down to an 8:15 mile
  • Exclusively training at or below 155 bpm for the next four months, his pace improved by over one minute
  • After nearly a year, his “pace at 155 bpm had improved to a blistering 5:20 mile”
That means that I was now able to burn fat for fuel efficiently enough to hold a pace that a year before was redlining my effort at a maximum heart rate of about 190. I had become an aerobic machine! On top of the speed benefit at lower heart rates, I was no longer feeling like I was ready for an injury the next run I went on, and I was feeling fresh after my workouts instead of being totally wasted from them.

After that change, Mark went on to dominate the various triathlon distances, including winning the Triathlon World Championship ten times. His 1989 victory in Hawaii began his streak of five consecutive victories at Ironman Kona. Even more remarkable, and unlike so many of his peers, he avoided injury and burnout while remaining healthy to this day.

Feeling Fresh After Every Workout

Feeling fresh after every workout is a dramatic change from feeling one run away from being too burned out to continue.

Our cells have a choice between processing fat or carbohydrates for energy. As our metabolic rate increases, we increasingly and then exclusively rely on the glycolytic pathway. The challenge for most people is that their athletic exertions immediately jump them out of the fat oxidation zone.

And just to be clear, we aren’t talking about fat as in visceral fat or carbs as in pasta piled high—we’re looking at the physiological mechanisms of how the body taps energy stores and converts it at a cellular level.

Crazily enough, the real challenge with Zone 2 training is simply how slow you need to go. At least at the beginning. Give it time, which few athletes do, and the complaint becomes that the pace is now too fast.

In fact, it is going to come as a shock to the system when you try to run at a slow enough pace to stay at or below your MAF threshold. When I began last month, it felt like I was running in slow motion, Chariots of Fire style. I felt like I needed to explain myself to any of my neighbors who were standing roadside and witnessing my pace. In fact, I started to, but thought, “What am I going to say?”

Cartoon with a family sitting around a couch, with the caption: No, this video of your father running is not in slow motion.

It got even worse when I trained at the local track. I imagined the other athletes taking me in and wondering what serious health setback I must be overcoming to be shuffling along at such a ridiculous pace.

Phil Maffetone actually counsels runners that they should run at night when it is dark, because most people won’t be able to sustain such a slow pace if they notice people watching them. The other unsettling aspect is that you will typically finish your workouts feeling like they were a complete waste of time and that now you need to go workout.

Rich Roll describes something similar in Finding Ultra:

I began with a very light jog to warm up, and after five minutes or so, I checked my heart rate to make sure I was in the proper zone—in other words, heart rate below 140 beats per minute. 150! It must be a glitch, I thought, since I was barely moving. The GPS signal on my watch bounced off an invisible satellite overhead to register my pace at a slovenly ten minutes per mile. No, it was accurate.

My aerobic system, it seemed, was simply so undeveloped that even the slightest jog had pushed my heart rate above my aerobic threshold into verboten gray zone terrain. I couldn’t believe it. In fact, I had to slow to almost a shuffle just to settle in the 140s. And when I hit even the slightest hill, I had to walk just to keep it in check. Meanwhile, I suffered the humiliation of allowing more than a few less-than-svelte joggers fly past me on the trail. Chris said it would take discipline to rebuild. I was now starting to understand what he meant.

This is why many coaches agree that the typical athlete who attempts Zone 2 training usually quits after two weeks from the sheer impatience of dealing with the tedious pace.

Let me put it in real life perspective. In my last half-marathon, I ran close to a nine-minute per mile pace to finish under two hours—my heart rate redlining the whole way. The pace when running past my neighbor, feeling the urge to explain myself? Well, after starting out at a zombified 14:35 pace, the next three miles edged up to 15:51 then 16:22 before finishing at 17:29.

I’m pretty sure most people can walk that fast. When you pass me on your next walk, be sure to slow down and say hello.

A cartoon showing a podium with three finishers: a turtle, a snail, and a sloth.

Calculating Maximum Aerobic Heart Rate

The more you research Zone 2 training, the more you’ll hear about how people have adapted the basic formula of 180 minus Your Age into something that specifically applies to them. Sometimes, these athletes are doing very specific lactate threshold readings throughout their workout, turning their fingers into pin cushions as they do repeated blood draws for pinpoint accuracy. I’ve done my share of this research on myself and am happy to share my findings.

First, let’s begin with the heart rate calculation. Here is the best MAF formula I’ve found:

  1. Take 180
  2. Subtract your age
  3. Take this number and correct it by the following:
  • If you do not workout, subtract another 5 beats.
  • If you workout only 1-2 days a week, only subtract 2 or 3 beats.
  • If you workout 3-4 times a week keep the number where it is.
  • If you workout 5-6 times a week keep the number where it is.
  • If you workout 7 or more times a week and have done so for over a year, add 5 beats to the number.
  • If you are over about 55 years old or younger than about 25 years old, add another 5 beats to whatever number you now have.
  • If you are about 20 years old or younger, add an additional 5 beats to the corrected number you now have.

Look familiar? For most people, this will work out to 180 minus Your Age.  

Customizing Your Maximum Aerobic Heart Rate

If you are the disciplined type, you can stop right there and use that calculation. But as you embrace the concept of Zone 2 training, you’ll find it challenging to embrace the actual tediousness of the beginning phase—which could last four months or more. You will hear things that will lead you to think that you should edge your number higher.

Let me provide some examples:

  • You will hear things like run at a pace in which “you can hold a conversation but you would prefer not to and the person on the other side of the call definitely knows you are exercising”.
  • Some believe that the exertion level corresponds well with nose breathing, and suggest restricting yourself to nose breathing through your cardio workouts.
  • It is all individual. Some people have naturally higher or lower heart rates than others.

Let me confess my own history of modifications. It turns out that I have an unexpectedly high (for my age) maximum heart rate—20 bpm faster than suggested by simple rules of thumb. While I wish this was an indicator of a youthful biological age, it is more likely another sign of my undertrained and out-of-whack aerobic system.

Unsurprisingly, no one modifies the formula to discover a lower training heart rate—the trend is always towards finding justification for training harder.

I suggest sticking to the formula. That target is most likely to correspond with your sweet spot for driving the specific metabolic adaptations you desire. It took me several months of research to fully understand the many nuances of those other suggestions. We’ll get to them all over the course of this series.

The Crucial Role of Mitochondrial Function

Dr. Peter Attia and Iñigo San Millán introduced some ground-breaking research:

“When looking at the Zone 2 efficiencies of world-class cyclists, recreational athletes, and people with diabetes…the interest in athletes is in large part due to [an] interest in diabetes because if you want to understand how to fix an example of arguably the most defective mitochondria, why not study what the perfect mitochondria look like?”

…The elite athletes have the perfect metabolism, and mitochondria are at the epicenter of metabolism and health. There is no other population on the planet with the mitochondria of elite endurance athletes.

Fatty acids are oxidized only in the mitochondria, and by recruiting mostly the slow-twitch muscle fibers during Zone 2 training, the body utilizes the mitochondria rather than converting glycolytic energy within the cytosol of the cell.

Now this isn’t to say that elite endurance athletes aren’t consuming glycogen. At times, they are actually consuming a lot of it. However, rather than accumulating as lactate within the blood, it instead is transported back to the mitochondria for reuse as energy via the MCT-1 transport mechanism.

An illustration of the inner workings of the cell

When we train in Zone 2, we are trying to get our body to transform the metabolic pathway for how it consumes energy.

Researchers at the cutting edge of cardiometabolic health have studied the entire range of the population, from sedentary individuals to elite athletes. They have examined pre-diabetic, Long Covid, Type 2 diabetic, cancer patients, recreational athletes, and Tour de France champions. When they look at the health problems there, they have learned enough to pose the question:

“Could the nexus of all that be a mitochondrial impairment?” — Iñigo San-Millán

I’ll get more into the science next week. Last year I finished last in a 92 mile bike race.  When I’d joke with other experienced athletes about finishing last, they would just smile and say So much better than a DNF. We’d then talk about those times where they just couldn’t complete a race and had to take a Did Not Finish.

Just finishing can be a victory. You made it to the end. We all want to avoid a DNF, or worse yet, failing to show up. But once there, none of want to fail to finish the race.

And yes, this is a bigger metaphor about living longer and healthier. Race day is just a day. Maybe two or more for ultra endurance athletes. But a life battling diabetes, getting slammed by Long Covid, having your immune system turn against itself during a battle with cancer—that’s the DNF we are hoping to duck.

There is no magic pill for increasing mitochondrial function. If there were, I’d take it. That means there is no substitution for Zone 2 training, and based on experience, it is probably to your advantage if you are not an endurance race competitor. Anyone who has done a race understands that the glycolytic energy pathways can be trained very quickly, and within eight weeks, you can be running or cycling or racing at a much higher level than being untrained.

A cartoon with a deer running on a treadmill while another deer dressed as a trainer says "Pick up the pace! Hunting season is two weeks away!"

Having a race or event on the schedule will pull you away from the base-building aerobic training that typically takes eight to eighteen months to become truly transformative. You don’t have to be coming off the lava fields in Oahu during the Ironman to feel confident about your health as you look around you and say I’m aerobic. I’ve got this.

In Mark Allen’s first race while Zone 2 training, he entered a half-ironman on pure base training, skeptical about how he’d do after exclusively training slow, and destroyed the field. He thought:

There’s something to this. And so then eventually over time, taking that heart rate concept, doing a lot of base work / aerobic training, and then eventually adding back in the speed work—just in the right amounts at the right times, I worked my aerobic pace down to about a 5:30 mile.

At 155 beats a minute, I’m running a 5:30 pace, and the other guys when I’m racing against them, their heart rates are 10 to 15 beats higher than mine. I’m so much less stressed out, my body has so much more reserve, and not only that, my training got much more consistent. All the niggling injuries went away. It was mind blowing.    

I’ve known these stories for about five years. I also knew that most people, myself included, give up after about two weeks because it starts so tedious. This time around is different, and that is because I did a deep dive into why it works. Most importantly, I learned why you’d want this aerobic base for more than just the two days a year someone might compete in an endurance event.

Next week, I’ll discuss the science and pathways around mitochondrial functionality and cardiometabolic health. If you can’t wait until that email, or you need an eyelid slamming instant cure for insomnia, I’ve already put that issue up on my website. Seriously, it seems impossible to discuss mitochondrial density without using syllabically dense language. Mercifully, it’s less than 800 words.

I’ve also included links to some extraordinary articles and podcasts about Zone 2 training. Lately, the topic is trending in the search algorithms, so hopefully our links will navigate you past the jumble. Feel free to jump into the discussion and see more of the source materials in the Always Invert digital garden.

Until next week, take it slow!

Join the Community

Join this conversation in the dedicated channel over at community.alwaysinvert.com

Articles we think you will like

Understanding Zone 2 Training: A Concise Scientific Overview

© 2022 Always Invert. All rights reserved.