Why Zone 2 is the primary training zone for triathletes — triathletes

You’ve heard it, you’ve talked about it, you’ve used it in your training: Zone 2 is the cornerstone of endurance training. But do you actually know what Zone 2 is, beyond the description “endurance training zone”? You’ve heard that you should spend a lot of time training in Zone 2, and that doing so will make you faster, but do you know how that actually works?

Whether you’re someone who likes to know the “why” behind your training or you’re someone who needs conviction that you really should be working this slow, this deep dive into Zone 2 will answer all the questions you have and maybe a few you haven’t thought to ask. You’ll come out the other side not only a smarter athlete, but also one who executes his workouts with intention and thus becomes fitter and faster. And really, isn’t that the point?

What is zone 2?

On the surface, Zone 2 is simply the second zone in a graduated system of training intensity. When we talk about zone 2, we are usually referring to its place within a system of 5, 6 or 7 zones. However, in some cases, training may be described using a 3-zone system, in which case what we are talking about would actually be Zone 1.

Here’s the thing about these multi-zone systems: No matter how many zones you select, the systems all depend on two physiological thresholds – lactate thresholds I and II, also known as LT1 and LT2. The three-zone system uses only those physiological boundaries for definition Training areaswhere 5, 6, and 7 zone systems divide the areas below, between, or above these boundaries.

You’re probably already familiar with LT2, which is the boundary it helps define High intensity training areasbecause that is what we generally call “Lactate thresholdThe first lactate threshold, or LT1, is an equally important but less well-known physiological threshold. We need to understand LT1 in order to understand Zone 2, and to understand LT1, we need to talk about energy systems.

Our bodies use two main energy systems to fuel our muscles for any activity longer than a few seconds: our aerobic and anaerobic energy systems. (We use a third system, the phosphagen system, to get very quick bursts of energy.) All of our energy systems produce adenosine triphosphate (ATP), the primary fuel source for our muscles.

Our aerobic system uses oxygen as a component of the relatively slow ATP production machinery (hence the name), and can produce fuel for hours upon hours in a well-trained athlete. Our anaerobic system is not dependent on oxygen and produces meaningful levels of lactate as a byproduct of the relatively fast but short-lived (only minutes at maximum production) ATP production machinery. Our aerobic and anaerobic systems are always working, producing ATP at all levels and zones of intensity, even if you’re sitting on the couch reading this article.

This brings us back to LT1. Under LT1, activity is powered almost entirely by our aerobic system, with a constant and very small anaerobic contribution as this system stalls in the background. These energy contribution ratios result in low and stable levels of lactate in our blood.

Once we move an atom above LT1, we have Anaerobic system It begins to accelerate, and blood lactate levels begin to rise. LT1 therefore represents the turning point between stable and increasing lactate levels in the blood, and the moment at which the contribution of our anaerobic system begins to rise.

Which finally brings us back to our original question: Zone 2 (or Zone 1 in a three-zone system) represents our heart rate, effort level, power and pace at which we work below LT1, and thus where we fuel activity almost exclusively with our aerobic system.

Why do we care?

Identifying Zone 2 does not necessarily explain why everyone gives so much importance to it in training. We’ll get into the details, but let’s start with the TL;DR version: everyone wants to get faster, and a big aerobic engine contributes greatly to speed – at lower intensities where the aerobic system dominates, but also at higher intensities more commonly associated with the anaerobic system. You can build this great aerobic motor by training in Zone 2.

A large aerobic motor is an aerobic energy system that produces large amounts of ATP at any given rate of oxygen delivery or heart rate. This engine does not live in one place inside the body, and it is not even a single engine.

Every muscle has its own aerobic motor, which is actually a collection of muscle mitochondria – organelles within each muscle cell that produce ATP during aerobic metabolism. greater Pneumatic motor It means muscles that contain larger groups of mitochondria and are highly efficient in producing ATP.

Below LT1, where your aerobic energy system provides 90+% of the ATP, or fuel, more and more efficient mitochondria means more fuel production, which means your muscles can work harder and you can move faster.

But above LT1, even after your anaerobic system increases ATP production, your aerobic system continues to function. In fact, your aerobic system works harder as your level of effort increases, until you reach your goal VO2 max – The maximum oxygen utilization rate and thus the upper limit of your aerobic system.

And since the aerobic power system works harder, more fuel production means your muscles can work harder and you can move faster, just like in the LT1. So a stronger aerobic engine delivers more fuel to your muscles at all effort levels, making you faster at all training intensities.

What is the benefit of training in Zone 2?

You can build this big air motor with your own air motor: the more you ask of it, the better it gets at its job. Specifically, utilizing your aerobic energy system stimulates mitochondrial adaptations that create new mitochondria, which increases mitochondrial density within the muscle, and improves the efficiency of mitochondrial ATP production.

And yes, you are using your air motor in all areas and effort levels, and it is working harder at higher intensities, but work done above LT1 comes at a cost. Above LT1, both aerodynamic and Anaerobic systems work harder, and the anaerobic system causes fatigue at a disproportionately higher rate than the aerobic system.

So the best way to spend as much time on your aerobic drive, so you can train today and again tomorrow and the next, is to find the perfect trade-off between the stress of aerobic training and the resulting fatigue load – which is of course Zone 2.

Zone 2 in triathlon training

To Use Zone 2 Effectively in Training In order to build that great aerobic engine and improve your speed or power across all effort levels, first, you need to be able to find your Zone 2 for each sport with reasonable accuracy. Field threshold tests It can help estimate power/pace and heart rate at lactate threshold (LT2), which can then be fed into standard zone curves to determine zone 2 pace, power or heart rate.

Laboratory threshold testing is the gold standard for determining not only your power/pace and heart rate at LT2 but also at LT1, which then determines your zone 2 peak. But lab tests aren’t generally useful for the average athlete, so we have ways to find Zone 2 outside of that.

Model Zone 2 ranges by sport and metric

• Swimming: 60-70% of maximum heart rate; 10-15 seconds per 100 slower than 1000m/yd
• bike: 81-89% of heart rate lactate threshold. 65-75% of threshold power (FTP)
• Being: 85-89% of heart rate lactate threshold. 78-86% of threshold pace (usually 2+ minutes per mile slower than 5K pace); 80-88% of threshold power

But the truth is that all these tests have some drawbacks. The limits found through field testing are estimates to begin with, and area curves are not customized to your physiological profile. Laboratory tests can be very accurate – but they only provide a snapshot of your physiological state on test day, and your speed, power and heart rate at LT1 and LT2 will develop alongside your physical fitness.

Additionally, testing in one sport does not necessarily result in a district placement in all three sports. So it’s helpful to know that your conversational threshold — the level of effort at which you’re trying hard but can still hold a conversation, speaking in full sentences without having to take a breath in the middle — is a surprisingly good threshold for the Zone 2 peak.

We often think of Zone 2, the work done below the threshold of conversation, as containing Rate of Perceived Exertion (RPE) out of 4 out of 10; Once you find a 4/10 RPE for one sport, you can generally translate it to the other two sports.

After you’ve identified Zone 2 in all sports using quantitative metrics, RPE, or both, you’ll want to spend a lot of time there, for all three sports, as each has a muscle-specific aerobic drive.

How much time should athletes spend in Zone 2?

Typically, you will devote approximately 70-85% of your weekly training minutes – across swimming, cycling and running, including warm-ups, cool-downs and recovery between intervals – to training in Zones 1 and 2. Zone 1, your very easy effort level, will generally only appear in your warm-up, cool-down, and recovery minutes, so the vast majority of those minutes will be spent in Zone 2.

And yes, especially while running, you can be cranky about spending too much time at what feels like a slow (but surprisingly comfortable) effort level. Stick with it for 6-8 weeks, and the shift in your speed or power at this effort level will be the evidence you need to maintain Zone 2 as the cornerstone of your training.