A CrossFitter’s Guide to Monostructural Conditioning

What I want to do in this article is give you a practical framework for understanding your engine, how we think about programming it, and how to actually execute the work in a way that moves the needle. There’s a whole universe of science around this topic. CP battery, lactate threshold, mitochondrial density. If you want to go down that rabbit hole, we can do that in another conversation. What I’ve found over 16 years is that when I get too obsessed with the science, my practical knowledge suffers. So we’re keeping this grounded.

Here’s what we’re actually trying to build.

The Four Components

Think of your engine as a house. Everything we do is trying to make that house bigger, stronger, and more connected from floor to floor.

Zone two capability is your foundation. It improves your ability to produce energy aerobically at a relatively low cost. That cost has two meanings: in the moment, how high is your heart rate and how much glucose are you burning, and over time, how much is it pulling from your other training. The athletes with a strong zone two foundation recover faster. They tolerate volume better. And they can sustain higher paces than other people without accumulating fatigue, because those paces, while hard for someone else, are easy for them. One zone two session doesn’t feel like it’s doing much. The accumulation of those sessions is what gives you the ability to do everything else.

Aerobic capacity is the square footage of your house. It is your ability to work hard for a long time. If you go to a competition and the 15 to 30 minute workouts feel like a different sport than what the athletes around you are competing in, that’s aerobic capacity. They are sustaining high output for a long time and you aren’t. Aerobic capacity also shows up as the ability to maintain output across intervals. You do three by eight minutes and the first one is your best and then you lose a few seconds on each subsequent interval. That’s aerobic capacity coming out. The athlete who maintains across all three has more of it. And when those recovery moments happen in a CrossFit workout, the 53 pound kettlebell swings, the double unders you’re good at, the transition between movements, the aerobic athlete is recovering in those windows while someone else is still elevated.

Anaerobic capacity is your staircase. Your ability to switch between things and move between floors. CrossFit demands this because the modalities change constantly. You might have heavy weights, then light weights, then a movement that requires a surge of effort because it’s your wheelhouse, or because someone is right next to you and you’re not going to let them walk away. Your ability to tolerate and repeat high intensity efforts, to survive those surges and come back for the next one, is anaerobic capacity. Paige’s way of putting it is exactly right: anaerobic work teaches you how to live closer to the red line without actually hitting it.

Power output is your ceiling. Your ability to go as hard as you possibly can in a short window. This one is important to understand in context. If you increase your ceiling, everything below it gets easier. The weight you’re moving or the pace you’re holding in a workout is a percentage of your total capacity. The higher the ceiling, the lower that percentage, the more sustainable your effort feels. The old saying in the early CrossFit days was if you want to get better at Fran, get your CrossFit total over a thousand. It sounds like a non answer. It’s actually the right answer. Increase the ceiling and everything underneath it becomes more accessible.

These four things work together. You can be really good at one of them and still have a session that drives you into the ground. That’s usually a sign that one of the other three isn’t where it needs to be.

The Gears Matrix

Before we talk about programming, you need to understand what a gear is. A gear is a speed. That’s it.

There’s no other explanation. A gear is a specific pace on a specific machine. Some gears are faster, some are slower. You have eight of them, corresponding to different time domains and intensity levels.

Here’s where it came from. The old approach to monostructural conditioning was pure variance: go long, go short, mix up the time domains, bounce around between two-minute windows and five-minute windows. That worked reasonably well for athletes who were already decent at this stuff. It wasn’t doing much for the athletes who were truly struggling with monostructural conditioning. I’m a meathead. So my solution was to force people to go either faster or slower than they wanted to by giving them a pace correlated to a specific workout. This week we’re running at an eight-minute mile. Next week we’ll change the duration and the work-to-rest ratio so you can run at a 7:45, then a 7:30. The athletes who did this started getting better at machines than the athletes who were already good at machines. That’s where the Gears Matrix came from.

The practical application: do one of the workouts, record your average pace when you’re done. That’s your gear for that machine and that time domain. Over time you build out all eight gears across all the machines. Then you use linear progression to get faster. One to two seconds per split. Fifteen seconds per mile. That progress feels invisible in a single week and compounds into something significant over a training block.

The matrix has another unintentional benefit: there are roughly 40 variations of these workouts across five machines. By the time you come back around to the same workout, enough time has passed that it feels like a benchmark. You get to test against a previous version of yourself without it feeling like testing.

If you don’t have a Gears Matrix yet, build one. An Excel sheet with your machines, your gears, and your dates is enough. Update it when you get a new number. Reference it when you’re programming your block. It’s one of the most useful pieces of data you can have on yourself.

How We Program It

The macro progression is slow to fast. Over a given block or training year, you start with more volume at lower intensities and gradually shift toward higher intensities at lower volume. Zone two heavy at the beginning, more anaerobic work as you build toward competition. In CrossFit specifically you have to be doing all four categories at once because the sport demands all four. But the ratio shifts. In the offseason you can spend more time building the foundation. In comp prep the anaerobic and power output work gets prioritized.

The clearest example of the slow-to-fast progression working well is the running transformation. We have turned multiple athletes who couldn’t run into high-level CrossFit runners. The process is always the same: a lot of zone two running in the fall, then aerobic running, then anaerobic running. It takes longer than people want. It works better than anything else.

Polarization keeps you from getting stuck in the middle. The 80/20 rule in endurance sports means 80% of your training time is spent in zone two and 20% is spent at higher intensities. In CrossFit it’s probably closer to 60/40, but the concept is the same. You don’t want to live in the middle, the heart rate range that’s hard enough to cost you but not hard enough to actually produce a meaningful adaptation. That range is sometimes called black hole training. High cost, low return. The way we stay out of it is by keeping the low intensity work truly low and the high intensity work truly high, and by not stacking high-intensity sessions back to back.

Workout structure forces pacing through limiters. Here’s how we manipulate total volume and work-to-rest ratio across the three categories:

For aerobic work, three example structures: 30 minutes of volume with a 15:1 work-to-rest ratio, 26 minutes of volume with 10.5:1, and 24 minutes of volume with 5.3:1. You can see the total volume decreasing and the work-to-rest ratio decreasing together, which means as the ratios get closer together, you’re being given more rest relative to work and forced into slightly higher output. These limiters are what make the pacing possible. You can’t go out too hot on a 15-minute piece with one minute of rest and expect to recover. You will find out. Fast.

For anaerobic work, three example structures: 18 minutes of volume with 2.4:1, 14 minutes of volume with 1.2:1, and 10.5 minutes of volume with 0.43:1. When the work-to-rest ratio goes below 1.0, the rest period is longer than the work period. That’s intentional at the higher gear sessions. We need you to rest enough to actually repeat the effort. The higher work-to-rest ratios at the lower gear sessions have less room for error. Go out too hot in a gear four session with a 2.4 ratio and you cannot recover. Your body will just be done with you.

For power output, the windows get much shorter and the rest gets much longer. Thirty seconds on, four and a half minutes off. Twenty seconds on, three forty off. Fifteen seconds on, two forty-five off. For continuous movements like running and biking. For row and ski where there’s a recovery element built into the stroke, you roughly double those rest periods. Sixty seconds on, four thirty off. The reason the rest periods in our power output sessions have come down compared to how we used to program them is that too much rest turns training into testing. You’re not building the ability to repeat power output. You’re just showing off that you can generate a high number when you’re completely fresh.

Zone Two: How to Actually Execute It

We did a full episode on zone two specifically. Episode 386. If you want the deep version, go there. Here I want to give you the practical execution pieces that I find most useful.

Output-based zone two beats heart rate-based zone two. Heart rate is the bumpers in bowling. You’re trying to stay between them, but the bumpers are just keeping you from going completely off course. Your actual target is output. Pick a wattage you want to be able to hold comfortably. Reverse engineer a starting point that’s well below that, the same way you build a runway in a Texas Method progression. If you want to hold 150 watts in zone two, you might start at 110 and add five watts every week or every other week.

The heart rate window we use is 160 minus your age on the low end and 180 minus your age on the high end. For me at 40, that’s 120 to 140 beats per minute. I never want to be above that ceiling. Going below it, especially early in a session or early in a block, is not a problem. Never above. The output progression is what I’m actually tracking.

Single modality is significantly more effective than rotation. If you have 45 minutes for zone two and you’re rotating between a rower, a ski erg, and a C2 bike every few minutes, you’re not getting the same adaptation as 45 minutes on a single machine. There’s a lot happening at the local muscular level during zone two work with the same repetitive motion in the same muscle groups. Rotating disrupts that. Stay on one machine for the duration.

The C2 bike is harder than it looks. For some machines, zone two is easy to access. You go for a jog and you’re there. The C2 bike is different. The wattage required to achieve zone two, especially in the first 20 to 30 minutes, is genuinely high for a lot of athletes. If you’re early in a C2 bike zone two progression and you’re finding zone one more than zone two, that’s okay. The goal is to increase your capacity while things remain easy. You’re not worried about the ceiling right now. You’re building from the floor.

Session length matters more than people want to admit. One to three sessions per week, 45 to 90 minutes of working time each session. The longer sessions are where real aerobic development accelerates. Forty-five minutes is a decent session. Ninety minutes is a better one if you have the capacity to do it without compromising everything else in your week. Beyond four and a half hours per week, the returns start to diminish for most CrossFitters.

If you can’t hold your pace, you need it more. This is one of those things that sounds cruel and is actually kind. If you sit down on a zone two session and you’re at 180 minus age immediately at a low wattage, that session is not wasted. It’s diagnostic. Your zone two capability is telling you where it is. Address the underlying factors, sleep, nutrition, accumulated fatigue, and then come back and keep going.

Heart Rate and HRV: Data, Not Instruction

Heart rate is useful as a data source. It becomes problematic when you try to use it as the primary instruction for how to train.

Programming entirely based on heart rate produces variable stimulus and variable adaptation. Two athletes at the same heart rate are having very different experiences depending on their fitness levels, their training history, and what their actual max heart rate is. Heart rate works better as an auditing tool, a way to check whether you’re staying in the zone you intend to be in and to review what happened during a session after the fact.

One practical note on heart rate accuracy: if you’re using a wrist-based optical heart rate monitor on an echo bike, your numbers are probably wrong. The upper body cadence is not in the frequency band most optical sensors are calibrated for. A chest strap solves this. It’s worth the investment if you’re taking the data seriously.

HRV is most useful as a macro recovery metric, not a daily instruction. The mental shift I’d encourage is to move away from “my HRV is low, today is going to be bad” and toward “my HRV has been trending down for three days in a row, something in my recovery needs to change.” Gamify it. When you make a behavior change, whether it’s adjusting your carbohydrate intake, your sleep schedule, your hydration, or your pre-bed routine, track what happens to your HRV over the following week. That feedback loop is where the real value is. I’ve had some of my best training sessions on days where my HRV said I should stay home. I stopped treating the daily number as a ceiling.

Testing

You cannot improve what you don’t measure. And the measurements have to actually reflect what matters.

We have three test types, one for each category.

Aerobic threshold test: Torta Misfit. This is a bike test you can do on a fan bike. Your score is your average output. We use a 40-minute window rather than the traditional 20-minute FTP test because CrossFitters can’t hold 95% of their 20-minute power for 60 minutes. The math doesn’t work the same way it does for dedicated endurance athletes. The 40-minute window is long enough to be meaningful without exceeding what’s relevant to the sport.

Anaerobic capacity test: The Kilowatt Test. Six rounds of four minutes on, one minute off. Your score is your lowest output across the six rounds. If you dominate the first five and fall apart on the sixth, your score reflects that. The four-minute window is genuinely uncomfortable. There’s nowhere to hide. The short rest period means the test is actually testing your ability to repeat capacity, not just show what your ceiling is. For running, the version is an 800 every five minutes for six rounds, with your slowest round as your score.

Power output test. Fifty calories on most machines, living in that one to two minute time domain. What’s important is that you retest the same thing you tested. The specific test matters less than the consistency of the test over time.

Anaerobic capacity test: The Cube Test. Four minutes on, four minutes off, four rounds. Score is total output across all four rounds. We use total output rather than lowest output here because CrossFitters have different strategies. Some go out hard and try to hold on. Some go out conservative and build. Total output captures what you actually produced regardless of how you chose to pace it.

The Percentage of Total Capacity Concept

There’s one more idea worth sitting with before you go do any of this.

The weight you’re moving or the pace you’re holding in any given workout is a percentage of your total capacity. The higher your ceiling, the lower that percentage, and the more sustainable the effort feels.

The classic example from the early days of CrossFit: if you want to get better at Fran, get your CrossFit total over a thousand. It sounds like a cop-out answer. It isn’t. The thrusters in Fran are 95 pounds. If 95 pounds is 70% of what you can do for a set of five, that’s a different experience than if it’s 50%. Raise the ceiling and the floor gets easier. This is true across every energy system. Better zone two wattage means everything you do at higher intensities is a lower percentage of your total output capacity. Better power output ceiling means your aerobic and anaerobic paces are a lower percentage of your max. The whole system rises together.

Build the house. Widen the foundation. Add the floors. Keep upgrading the ceiling.

That’s the engine.

– Drew

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