Why is My “Z2” So “Slow?”

Make the gains you want by understanding the physiology, adjusting your perspective, and embracing a growth mindset

Earlier this summer, one of the athletes I work with sent me a meme that showed a man “running,” although it was the kind of running you used to do in soccer practice in between sprints when you wanted to walk but you needed to make it look like you were still running so your coach didn’t tack on even more sprinting. In the meme our athlete is jogging, and in the background ananother person walks past him, moving faster than his “Z2 Shuffle.” The meme caption reads “Zone 2 Runs Be Like…”

“Z2 Training” has experienced a moment in the past six years, ever since Peter Attia had Inigo San Millan on his podcast to talk about longevity (not performance!), and Attia’s vast audience picked up the term and ran with it, trumpeting the benefits of “Z2 Training.”

Like many fads in endurance training, “Z2 Training” is poorly understood and even less well applied to effective training. It joins other faddish concepts that have shown up in the endurance world over time like HIIT, SIT, Time-Crunched Training, the Ketogenic Diet (and it’s big brother, “Metabolic Efficiency”), and “The Norwegian Method,” which is just sensible endurance training under a nationalistic wrapper (which most Norwegians athletes dislike, by the way, calling something general specific to their country).

Today we’re going to try and debunk the myths associated with “Z2 Training” and show you how the general concept of aerobic conditioning (which would be a better term for “Z2 Training,” except that it’s not catchy enough) will definitely make you a better endurance athlete, as long as you can be patient and start loving your easy training. Ready? Let’s go.

Z2 Is Nothing New

As alluded to above, “Z2” training is nothing new. Ever since Arthur Lydiard started figuring out how human bodies get faster through endurance training, most successful athletes have done most of their training at an easy, sustainable intensity. Lydiard’s 800m runners and marathoners both ran over 100 miles a week, with the marathoners sometimes getting up to the 130 mile mark, but really it should be clear that volume works, if it’s making sub-2:00 800m runs AND 2:10 marathons possible on roughly the same amount of training.

But what IS this intensity in the first place? We could get deep into the weeds, here, but that’s not going to help with clarity too much. It’s basically an easy to moderate intensity, one where you can hold a conversation with someone else (remember, folks—a conversation is something where you say something and then someone else gets to say something), or if you’re training alone it’s right around where your breathing becomes audible. It’s pretty easy.

I can already hear you asking “if it’s easy, how is it going to help me go sub-9 for my Ironman, or sub-4:30 for my half-ironman, or under 40’ for my 10k, or etcetera, etcetera…”

Great question, and we’re going to address that issue down below. But here are the biggest reasons why your “Z2” is “slow” *at the moment*, and that “at the moment” is the biggest idea I hope you take away from today, but we’ll get into that soon.

  1. You’re new to endurance sports

  2. Your natural physiology tilts more towards sprinting (efforts under 20 seconds) or lifting/throwing heavy things OR you’re coming from a sprinty/lifty sports background

  3. You struggle to accept that training easy will work, so you train at “race pace” (or what you think is race pace) all the time

  4. You have a fixed mindset about what “fast” and “slow” mean

  5. The Problem with Pros

You’re New to Endurance Sports

This is the easiest one, and if you’re in this boat I hope we can fix this today.

Your body is inherently lazy. Now, before you get all mad at me, think about this. Remember that, despite our modern accoutrements, we as a species have spent much more time as hunter-gatherers than agricultural-industrialists. Our bodies still think that there are dangerous threats such as wild animals and natural disasters around most corners.

As a result, our physiologies aim to conserve as much energy as possible, in order to get away from that lion or sprint up the hill before the flood washes us away when those disasters strike. Our physiologies resist expending energy, but when our bodies see a repeated need they grudgingly adapt to meet that need. If you’re a persistence hunter and need to run/walk for days in order to kill that Ibex, your body will adapt to that demand over time.

Did you catch that “over time?” That’s gonna be important today.

When we decide to pick up endurance sports, our bodies find the efforts unfamiliar and alarming. Since the body hasn’t experienced the demand of running 5k, or swimming 100 meters, or riding in a peloton, it does its best, marshaling its resources to meet this new, unfamiliar physical demand. If you remember what it felt like to go for your first run, you will probably remember the sensations associated with extreme effort: gasping for breath, burning muscles, an overwhelming urge to STOP after only a few minutes.

Why? Well, your body hasn’t yet adapted to this new “threat,” which is how it perceives the demand you’re placing upon it. You haven’t yet developed the “endurance infrastructure” you need to deliver the required oxygen to your working muscles. The gasping for breath and burning muscles are signs that you are doing an unsustainable activity and that you will need to slow down soon.

This is the moment that most nascent endurance athletes quit. “This,” they say, with incredulity, “is how this will always feel? No thank you.” And they’re not wrong to think that! If going out for a run or a ride always felt like maximal intensity, you wouldn’t want to continue, either.

In order to endure effectively, here are the elements of basic endurance infrastructure:

  1. A heart with thin but flexible chamber walls that can pump A LOT of blood per heartbeat (this is called “stroke volume”)

  2. A body that has a high amount of red blood cells and plasma, the liquid component of blood (this is called “blood volume”)

  3. A large network of tiny blood vessels that can “drop off” oxygen at your working muscles (those blood vessels are called capillaries and this term is called “capillary density”)

  4. A large number of mitochondria (”THE POWERHOUSE OF THE CELL,” thanks, 7th grade life science!) in the cells of your working muscles that function correctly (these two terms are “mitochondrial density” and “mitochondrial function”)

  5. A body that can use carbohydrates and fats (and a few other energy sources) economically. This usually gets called “metabolic efficiency,” but as someone smarter than me once said, “metabolic efficiency is just a fancy term for getting fit.”

When you begin endurance training, and for much of the following year after you begin endurance training, you will not have these abilities developed. Does this mean you won’t be able to do endurance sports? Not at all, but your body, as we pointed out above, will meet the need somehow, and the way it tries to meet that need is through other pathways. Those other pathways are the ones that leave you gasping like a fish and needing to walk.

So when you are new to endurance sports, basically ANY effort above a brisk walk is going to be unsustainable after a few minutes. When you determined your “Z2” intensity, likely through some sort of ramp test or time trial, the test gave you a heart rate range for your “Z2.” If it is a good test (very few guarantees there), the heart rate range it gives you will be your highest sustainable aerobic effort. In other words, the highest effort you can maintain without having to slow down or stop.

But as we just saw, since you don’t have the endurance infrastructure developed, yet, ANY effort above a brisk walk is unsustainable, which is why you’re “running” at a shuffle where elderly people pass you on the sidewalk.

If this is you, you can jump straight down to the “What To Do About It.”

Your Physiology is More Tuned to Sprinting or Lifting Heavy Things

Everyone is unique, with unique physiological properties. Some people are “sprinters,” or those that naturally can expend a LOT of energy in a small amount of time. These physiologies usually are good at picking up heavy things and sometimes even throwing them around. In track cycling there are “Sprinters” and “Stayers.” Sprinters can fire a pound of bacon into the stratosphere with their power numbers but can’t jog around the block, while Stayers get sand kicked in their face on the beach but can literally ride circles around you nearly forever. People who naturally can sprint or lift heavy things have great gifts, but if those people WANT to do endurance sports, they are going to have to focus extra hard on developing their endurance infrastructure, which will be difficult, since they have the sprint/lift/bacon cannon infrastructure developed, and you cannot be all things to all sports. I’m sorry, but if you believe you can both climb mountains relatively quickly AND sprint effectively, you are either delusional, doping, or one of a very few true genetic freaks.

If you are good at lifting and sprinting, one characteristic of your heart is that it will have thick chamber walls that can withstand the considerable internal pressure of those two activities. As we pointed out above, good endurance athletes have thin chamber walls that can flex and accommodate a lot of blood—they have a high stroke volume. This is one of of the reasons that, if you are a natural sprinter/lifter/bacon cannon OR if you are coming from a sprinting/lifting/bacon-projecting sport, “Z2” will feel slow to you—your physiology assumes it is going to be firing bacon into the stratosphere, and it uses those tools. But as we saw above, those tools will leave you gasping like a fish within a few minutes.

You Do Not Believe

Since our bodies adapt to the stimuli we throw at them, your physiology is essentially “you are what you eat,” or, in this case, “you are what you train.”

If you go hard all the time, or do sprint training, thinking that doing so will make you faster as a marathoner, well, I have a boat to sell you.

First, though, let’s set aside any specious ideas I might be misunderstood as saying. This paragraph is if you ONLY go hard or race pace or sprint pace all the time. Fast, hard training is a necessary element in any training program, but it is a TINY percentage of your overall training. What I am talking about here are the athletes who think that “if I run/swim/bike slowly, I won’t ever be able to go the speed I want to go in a race.” This is an understandable misconception, made worse by coaches out there who preach “specificity” in all their training. Yes, just like speed work, specificity is an important element in a training program, but it comes at the end of a training program, in the final months before your big race.

It’s hard to understand athletes that think like this. If you extrapolate this thinking to its logical conclusion, you would have to run a marathon every time you went out to do a training run. Obviously that would be untenable, boring, and destructive. On the other hand, it would also be insane to train for a marathon by only doing 100m sprints, but there are plenty of coaches and athletes who seem to believe this.

If you train at race pace all the time, you are only expressing the fitness you currently have. Yes, you will place some demands on your body, and your body will adapt to reflect those demands, but if you train at race pace all the time, or try to go fast all the time, or try to run a marathon for all of your training runs, you are going to amass more fatigue than fitness, and when we are in that realm danger lurks, because too much fatigue means you are on the road to injury, sickness, and burnout.

And when we develop the wrong energy systems, our body is not used to the relatively lower demands of Z2 training. If you train your body to be a sprinty/lifty/bacon-cannon body, you will experience the same issues we talked about above: you will not have the physiological capabilities to move faster than a walk when you are at Z2 heart rates.

You Think That “Fast” and “Slow” are Fixed Terms

Finally, the biggest reason your zone 2 is slow?

You’re expecting too much, too soon.

Fixed mindsets believe that, well, things are fixed in place, unchangeable. These athletes try zone 2 training, discover everything above, and say “well this is clearly not for me,” which is a tragedy, because if they gave it time, they would discover that while their effort stays the same (and we can measure effort with heart rate or power), they go faster at that particular effort! This is the magic of endurance training: as your body adapts, it gets more economical. Here’s an example from my own training. I have (somewhat reluctantly) started running again recently. Because I am a creature of habit and my time is short, I usually run the same loop here in Bend. Here are my paces and heart rates over the last six weeks of adding running back in:

9/4/25: 8:21/mile, 135 BPM, pa:hr decoupling 12%
9/15/25: 8:55/mile, 126 BPM, pa:hr decoupling 7%
9/19/25: 8:45/mile, 126 BPM, pa:hr decoupling 5%
9/23/25: 8:41/mile, 124 BPM, pa:hr decoupling 5.2%
10/3/25: 8:07/mile, 127 BPM, pa:hr decoupling - 5.76% (hr and pace got closer together, not farther apart!)
10/7/25: 8:30/mile, 130 BPM, pa:hr decoupling < 1%
10/9/25: 7:57/mile, 125 BPM, pa:hr decoupling 7%
10/12/25: 7:58/mile, 128 BPM, pa:hr decoupling 6%
10/15/25: 7:57/mile, 132 BPM, pa:hr decoupling 6%

What jumps out at you here? To me it’s the fact that even though my HR remains the same (firmly in the middle of my “Z2,” although at Campfire we call this intensity Z1 because, well, it’s the most important intensity and calling it Z2 is…weird?), my average pace over the course of not even a month drops almost a minute, from the high 8s to the high 7s.

We’ve all heard Greg Lemond’s quote “It never gets easier, you just go faster,” which I would like to rewrite as the quote you saw at the top of this article:

“’Z2 Training’ never gets harder, you just go faster.”

And this is the beauty of this type of aerobic conditioning, and the whole point of this article (and my coaching, actually): if you train easy most of the time, you will improve all of the physiological abilities you need to improve that will support harder training, too, but you need to do this work first. And believe me—once you do shore up your aerobic conditioning, your Z2 will get a LOT faster. So fast, in fact, that you might begin to dread your Z2 sessions, because even though the intensity is the same, speed can beat you up.

So if you came here asking “Why is my Z2 so slow?” I have a somewhat harsh answer for you:

It’s because your aerobic conditioning sucks.

But I also have good news! Changing that fact only requires you primarily swimming, riding, running, skiing, rowing, or skating at an easy, enjoyable effort. Because this is, after all, supposed to be fun.

And don’t worry—there will always be some hard work, and it will be VERY hard work, but in order to go very hard, you also need to go very easy.

An Aside: The Problem with Pros

One abiding “feature” of triathlon and many other endurance sports is the proximity of professional athletes. They race on the same course, often at the same time. Very few other sports offer that kind of intimacy with the best in the game, and most professional triathletes are kind and generous with their time, which makes them seem even more accessible to the rest ofus. But as with most features, there can also be bugs.

Because of this proximity and the fact that professionals make difficult things look easy, we can imagine our abilities as closer to them than those abilities actually are. So when we see pros riding 28-30 miles an hour for four hours and then running a marathon in 2:40 afterward and making it look relatively (the key word here is “relatively”) easy, we can imagine that performances like those are closer to our abilities than they actually are. We think that if riding that fast would be hard for us, it must be hard for them, too, so we should be riding hard during the bike leg of a triathlon.

But professional Ironman athletes have aerobic conditioning in spades. That’s most of the training they do, actually, and it’s what allows the men to race an Ironman close to 5 w/kg and the women to race close to 4 w/kg. A male Ironman pro’s “Z2” is likely to be somewhere around 300-340 watts these days, and the women aren’t far behind: the mid-to-high 200s. When you weigh 70 kg and you can hold 320w in Z2, you are going to be riding very, very fast.

But they’re still in their Z2! And if we try to copy what the pros are doing because they are right over there, we are going to run into some real problems. Many high-level amateurs—or those that aspire to be high-level amateurs—misunderstand this fact, and the result is that they train (and then race) too hard, blowing up in practice or blowing up on race day, neither of which is desirable.

So instead of copying the pros on race day, copy their training, which is, as I’ve pointed out above and as many others have pointed out before me, mostly easy-to-moderate training. If you don’t believe me, go and read Niels Van Der Poel’s account of the training for his 2022 speed skating gold medal and you’ll get an eye-popping account of his “Z2” training (which he does not call Z2).

An Apology to Peter Attia

Peter Attia is primarily focused on longevity, not performance, which he has said many times as the endurance world has run away with what he was trying to say. He is clear that if you want to perform at endurance sports, you need to do SOME hard training, but he is mostly thinking of longevity, and his program using Z2 (and what he calls Z5) is for a totally different purpose. Remember that when you are trying to analyze what people are doing, you also need to consider their goals.

Conclusion

There’s not much more to say here. Z2 training is nothing new—just regular endurance training given a new wrapper. But if you’ve been wondering what you can do to bring your experience of “Z2 Training” closer to what you believe it should be, then follow the steps above: keep it slow, do the work, stop joking about it, and be patient.