Building your engine.

The engine comes first.

Alright. We've talked about what power means, how to read your numbers, why your zones might be wrong, what durability is, and why textbook periodisation doesn't work the way you've been taught. That's a lot of concepts. Now we need to actually build something.

And the thing you build first is always the engine. Your aerobic base. The foundation that everything else sits on.

I know this isn't sexy. Nobody puts "I did three months of Zone 2" in their Instagram bio. But it's the single most important block of training you'll do in any year. Because without the aerobic base, intensity doesn't stick. Without the endurance infrastructure, your durability is built on sand. Every shortcut you take here shows up later, usually at the worst possible moment, in the last hour of the ride that matters.

So let me walk you through how I actually build this.

Building the base.

This is an aerobic sport. You need an aerobic base. And I'll be honest, "base training" has no scientific definition. The approach was popularised by Arthur Lydiard in the late 1950s and early 60s for his runners, and the concept stuck because it's useful even if the label isn't precise. What is scientific is the adaptations underneath it. So I'm not going to spend ten minutes telling you things that anybody who's been around cycling for more than a year already knows. Base training matters. You know that. What I want to do instead is give you three specific reasons why this work does what it does, because most people have never had it explained this way, and it changes how you think about every endurance ride you do.

First, Zone 2 builds your fat-burning machinery. And I mean that literally. There are transport proteins, CD36 and the FATP family, that physically move fatty acids into your mitochondria to be burned. Maunder's 2023 work showed that a model containing these transporters explained around 87% of the variation in fat oxidation capacity between cyclists. Zone 2 is fatmax training. You're not slowly building your VO2max. Inglis showed in 2024 that higher intensities do that more efficiently. What you're building is the fuel system that lets you spare glycogen deep into a ride. That's why you've still got something left at hour four when everyone else is fading. That's durability at the metabolic level.

Second, Zone 2 triggers adaptation through a different pathway than intensity. This is the part most people miss. Low-intensity work stimulates mitochondrial biogenesis through calcium signalling. High-intensity work does it through ATP depletion. They're not the same stimulus at different doses, they're complementary. That's why you need both eventually, and why one doesn't replace the other. You can't interval your way to what volume gives you.

Third, you're building a bigger heart. Cardiac remodelling. Stroke volume. Brown and colleagues, 2020, measured this directly. Elite cyclists had left ventricle end-diastolic volumes of around 162 millilitres versus 104 in untrained controls. That's roughly 56% larger. A structural change that takes time and consistent aerobic volume to develop. There's no shortcut to it.

So when I say "build the base," that's what I mean. You're building fat oxidation capacity, mitochondrial infrastructure through a pathway that intensity can't reach, and a structurally bigger heart. That's the platform.

And here's the thing that ties it together. Zone 2 isn't producing adaptations that intensity can't. A 2025 expert consensus and the broader research are clear on this: different intensity zones stimulate similar aerobic improvements, stroke volume, capillary density, mitochondrial function, through different signalling patterns. The advantage of Zone 2 is not that it's magic. The advantage is that you can do five hours of it. You can't do five hours of VO2max intervals. The steady-state metabolic nature of this intensity means you can accumulate far more total aerobic work before the stress becomes non-functional. The sustainability is the advantage.

And if the platform is shaky, the intensity just creates noise. You get temporary spikes in fitness that don't last. You build numbers that look good in week eight and disappear by week twelve. I've seen it hundreds of times.

Now, and this is the part that I think a lot of people get wrong, where you ride your endurance matters. Zone 2 is not just one intensity for everybody.

Well-trained cyclists have high lactate flux. They clear lactate efficiently at lower intensities, but they also accumulate metabolic strain faster at the upper end of the traditional Zone 2 range. I see this all the time. A national-level rider will tell me that 75% of FTP feels quite hard after three hours. That's because for them, it is. The metabolic cost is higher than it looks on paper. Whereas a newer rider at 70 to 75% of FTP can often sustain that for hours without the same strain, because their systems aren't developed enough to generate the same metabolic load.

And here's something that reinforces this. When well-trained endurance athletes are profiled in the lab, they spend most of their low-intensity time at what we'd call Zone 1 by lactate, under about 1.1 millimoles per litre. That sounds too easy. But because their lactate clearance is so good, they can hold that lactate at a heart rate that looks much higher than a textbook Zone 1 would predict. What looks like easy riding to them is physiologically doing what Zone 2 does for everyone else.

How you actually monitor this in real time, the practical tools for dialling in the right intensity ride by ride, that's coming in the five golden rules chapter when we get into execution.

Roete's 2025 study of World Tour women showed the difference between highly successful and less successful seasons wasn't more high-intensity work. Zone 4 and above was identical. The difference was more low-intensity volume. And Christensen and colleagues, 2024, ran the matching experiment in elite men: seven weeks of added intervals, with one group keeping their moderate-intensity volume and the other cutting it by about a third. The fresh-state time trial improved equally in both groups, but the fatigued-state time trial, the one that actually measures durability, didn't improve in the group that cut volume. You kept the capacity. You lost the access. That's the cost of skipping the base.

Emphasis, not exclusion. The base phase is aerobic-priority, not aerobic-only. There's room for variety, tempo efforts, neuromuscular work, short openers, as long as the primary intent is building the engine. Almquist showed in 2021 that endurance cyclists who added short sprints to their low-intensity rides better preserved their 20-minute power output compared to those who kept a steady pace. You're not contaminating the base by sprinkling in some intensity, you're making it more robust. What you're not doing is structured threshold intervals or race-specific intensity over and over again.

Volume. How much do you need? As much as you need to make adaptations, but less than makes you too fatigued. That's the honest answer, and it's not always the answer people want to hear, but that's as simple as I can make it. If you've got 6 to 8 hours a week, most of that should be aerobic work with intent. If you've got 10 to 12 hours, you can go bigger. The principle is the same, the majority of the work is building the engine.

How long. This is where signal-based thinking applies. The base phase runs until you see the adaptation. For most riders, that's six to ten weeks. The signs: resting heart rate drops, heart rate at Zone 2 power drops, aerobic decoupling improves, RPE drops. When those signals appear and stabilise, the base has done its job.

The durability dial.

Within the base phase, and within your regular long rides generally, there's a decision tool I use that I call the durability dial.

The idea is simple. On any given long ride, you have a choice: do you ride for time at a steady effort, or do you add some fatigue-state work, efforts in the last hour when you're already tired? And the answer depends on where you are in your training and what the signals are telling you.

Early in a block, when you're building the base, the dial is turned down. Just ride. Accumulate the time. Let the aerobic system do its thing without adding extra stress.

As the block progresses and the base starts to solidify, your decoupling improves, your heart rate stabilises, your legs stop feeling dead the next day, you start turning the dial up. Maybe you add some tempo in the last thirty minutes. Maybe you do a set of short efforts at the end of a long ride, when you're already three hours in. You're asking the body to perform under fatigue. That's durability training in action.

And there's evidence for why the long ride itself matters. Zanini's 2025 study, done on runners but the principle holds for any endurance sport, found that athletes who regularly ran for more than 90 minutes had roughly half the economy deterioration over a long effort compared to athletes who never trained that long (a 3.1% versus 6.0% rise in oxygen cost). The duration of the longest weekly session correlated strongly with durability. It explained around 45% of the variation between athletes. The long ride isn't just volume accumulation. It's a specific durability stimulus. And what you do with the dial at the end of that ride determines what kind of stimulus it is.

The dial isn't a plan. It's a week-by-week decision based on where you are. And that's the point. This is the apply/observe framework from the periodisation chapter, applied to a specific situation.

Structuring the year.

There are two ways to think about structuring your training year, and which one fits you depends on whether you've got a specific event you're building towards or not.

I think of them as finite and infinite.

Finite is what most people picture when they think of a training plan. You've got a goal event, a date on the calendar, and everything works backwards from it. You build, you sharpen, you peak, you perform. It has a start and an end. That's the traditional periodisation cycle.

Infinite is for riders who aren't targeting a specific event. Masters riders, people who ride sportives, group rides, people who just want to be fit and ride well year-round. You're rolling through blocks, base work, some intensity, back to base, reading signals, adjusting, never forcing a peak for a date that doesn't exist. The goal isn't a race result. It's sustainable progression over time.

Most of the people watching this are probably closer to infinite than finite. And that's fine. You don't need to manufacture a fake peak to justify your training. You need a system that keeps you progressing and keeps you healthy. The infinite approach gives you permission to do that properly. And that's a big distinction, probably 70% of the athletes I've worked with aren't chasing a specific goal event. They just internally want to do better. That's enough.

The finite model (building towards an event). When I'm building towards a goal event, each block has a specific focus, a key metric I'm tracking, and a testing protocol. The structure typically looks like this:

• Preparation (4 weeks). Train to train. This is optional and gets cut off pretty easily, but when you have the time, it's about getting ready to train properly. Consistency, addressing individual needs, establishing baselines.
• Base 1 (4 weeks). Extensive aerobic. Key metric: time in zone. This is the engine-building we've been talking about in this chapter. Just accumulate quality aerobic time.
• Base 2 (4 weeks). Intensive aerobic. Key metric: power at LT1, your aerobic threshold. You're lifting the floor, pushing the aerobic engine higher. More tempo work, more structured aerobic efforts, and this can include a higher aerobic zone.
• Base 3 (4 weeks). Aerobic event-specific. Key metric: power at CP. Now the training starts reflecting the demands of the event while still building the aerobic platform.
• Build 1 and 2 (8 weeks). Limiter-focused. Key metric: increased power. This is where it gets individual. Whatever the rider's specific limiter is, VO2max, sustained power, repeatability, that's what these blocks target. Two blocks because limiters take time to shift.
• Peak (2 weeks). Individual-specific. Race simulation, coalescence, stacking the elements together. You're not building anymore. You're sharpening.
• Perform. Hit the goal. Do well. Win.

That's roughly 22 to 24 weeks, built backwards from the event. Every transition point is a signal check. And the annual plan sets direction. It doesn't change week to week. Weekly plans execute within it.

The infinite model (no target event).

Rolling blocks. You cycle through base-style and build-style blocks without a forced endpoint. Base 1, Base 2, Build 1, back to Base 1. Or Base 2, Base 3, Build 2, back around. You're touching different things, you have a goal, but you're not neglecting other areas. You usually get back to something just in time after you haven't worked on it for a while.

No forced peaks. You don't taper for nothing. If an event pops up mid-block, you can race off your current fitness. Sometimes that's Base 3-style work, and for a gran fondo, that's generally enough.

Signal-driven transitions. You move between blocks when the signals say you've absorbed what you came for, not because your training plan has you moving through.

Sustainability is the goal. The infinite approach works better with athletes who have more time, usually that's older athletes, not always. Riders managing injuries or life constraints. Anyone who values control and consistency over peak performance on a single day.

Either model.

What if you only have 5 to 6 hours a week? Same principles, both models. Shorter blocks, maybe three weeks instead of four, so two work weeks and one rest week. Tighter intensity phases. More emphasis on making every session count. You can't afford junk volume, every ride needs an intent.

Built-in flexibility. If you get sick in week 6, the block extends. If you adapt faster than expected, you move on. The training plan is the guide, not the contract.

Handling disruptions.

Missing a week isn't a crisis. Detraining research shows you don't lose meaningful fitness in 5 to 7 days. What you lose is the momentum of the block. So when you come back, you don't restart, you recheck the signals, get an idea of where you are, and pick up where you left off.

Illness resets the block. If you're sick for more than a couple of days, you've lost training stress and potentially accumulated non-training stress. The base phase might need to extend. The intensity block might need to restart. Read the signals, not the plan.

Sometimes you push through anyway. This is the big one. Sometimes when things are really going badly, not just illness but life, I'll push an athlete through to the next block even if the signals aren't at 100%. Because your body's only going to handle so much. You don't want to drag out a bottom-up base phase for six months. It's worth shifting things even for a little while and then coming back to them.

Travel is an opportunity, not a disaster. Hotel gym, running, bodyweight work, rest, all of these are valid responses to travel. The worst response is trying to replicate your normal training in a disrupted environment and doing it badly. Some of managing this is just being aware that the travel is going to happen, so you build when you have the window. A smart athlete does what they can when they can.

Close.

Building the engine isn't complicated. It's consistent aerobic work, applied with patience, adjusted based on what your body is telling you. The durability dial, the signal-based block structure, these are all ways of doing the same thing: building the platform that everything else depends on.

The next question is: once the platform is there, what do you put on top of it? Which workouts actually earn their spot in your training week?