Cycling is best for zone-based training

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

1. Training methods

In endurance sports, such as running, swimming, nordic skiing, rowing — and, of course, cycling — training of any degree of seriousness is done via methods based on intensity zones.

The use of the zones in those methods may be as follows:
• pyramidal — lots of low-intensity work, decent amount of threshold, a bit of hard efforts,
• polarised — also lots of low-intensity, almost no threshold, the rest is hard efforts,
• low-intensity — the majority of effort is easy-ish (endurance and, much less so, recovery),
• high-intensity — vice versa, most of training done in hard efforts (VO2 max and/or sprinting),
• threshold/sweet-spot — way more time around the threshold zone than in pyramidal (while usually still maintaining significant volume of low-intensity).

On top of that, there’re numerous periodisation techniques — meaning shifting the focus on different zones, and their combinations, over time.

While the classification above gives you a rough idea, there’re a gazillion various methods combining intensity and periodisation with nutrition and rest tactics resulting in an infinite number of combinations: HIIT, SIT, HVLI, Norwegian, Microcycle, whatever.

I’m not going to dig into that deep hole right now, but instead let’s talk about what exactly those zones are, and how do you measure them to use them. That should be most helpful for non-specialised training of amature athletes and healthy-cautions individuals.

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

2. Training zones

There are several zone models ranging from 3 to 9+ zones. I will build up my explanations up to 7, as I have good reasoning why.

When explaining the training methods above, I started with 3 zones: low-intensity, threshold, hard efforts. Then I divided low-intensity into recovery (zone 1) and endurance (zone 2); hard efforts comprise VO2 max (zone 5) and sprinting (zones 6 & 7 — bear with me). What I have previously been referring to as “threshold” (in a 3-zone model), can be separated into anaerobic threshold (zone 4) and tempo (zone 3) with the mentioned sweet-spot in between them.

(Yeah, sorry for the sometimes confusing terms — especially involving the word “threshold” — it wasn’t I who invented and developed all that, and there are more than one thresholds involved.)

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

3. How to outline

Now, while the very idea of zones is quite intuitive — those are just levels of intensity/hardness — before I explain each and every zone, I better start elaborating on where to draw the line between them, which is not always straightforward.

A) By heart rate

The conventional scale goes as follows:
zone 1 — less than 69 % of anaerobic threshold heart rate,
zone 2 — 69–83 %,
zone 3 — 84–94 %,
zone 4 — 95–105 %,
zone 5 — 106 % or more,
zone 6 — up to maximal
zone 7 — irrelevant (it’s so short your heart will not even get going).

All that is for cycling — your heart rate at the same zone will be lower for this sport (as the heart only needs to supply propelling leg muscles, but less so stabilisers — and even less your arms, etc.); higher when running, and the highest when nordic skiing (as you use your arms to push with poles, as well as more specialised stabiliser muscles for skating step).

While by hear rate is the most accepted method, it is so flawed. You see, your heart rate may vary depending on many factors, including:
• how tired (or excited/stressed) you are,
• when was the last time you ate,
• outside temperature,
• your cadence, etc.

So, the heart rate when spinning in the summer heat right after a meal on a busy downhill road could be dozens BPM higher than when grinding in the cool on a settled stomach and on a quiet stress-free road — all that at the very same intensity level.

That means that heart rate is not just imprecise — it is so inaccurate that you may realistically miss a whole zone, unless you have enough experience to take into account all those factors. At which point, you could probably just do it based on perceived exertion (more on that later).

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

B) By generated power

Provided you have a means to measure your power output, everything gets much more high-definition.

First, the scale:
zone 1 — less than 55 % of anaerobic threshold power,
zone 2 — 56–75 %,
zone 3 — 76–90 %,
zone 4 — 91–105 %,
zone 5 — 106–120 %,
zone 6 — as much as you can with a hint of pacing,
zone 7 — all-out like your life depends on it.

By now, you may have noticed that the scale is built around anaerobic threshold (heart rate, power) in the center of it. As far as heart rate, there exist zone models based on max HR — but those are even more flawed, so I don’t even want to elaborate on that. (And by the way, your max heart rate will also be different for different sports.)

That’s where I’ll start describing the zones themselves. The central zone 4 — anaerobic threshold — is in fact determined by a certain point in increasing intensity where your muscles start producing lactate at a sharply increased rate. This is what’s called anaerobic threshold (or LT2).

Before that point, your body can still tolerate the steadily increasing lactate levels, but as soon as you hit your anaerobic threshold (LT2), the lactate starts building up so fast that in just several minutes its concentration will physically prevent you from continuing at the same intensity. It’s not just that it will be painful, but your muscles will literally shut down.

Thus, staying in zone 4 means fluctuating just around that anaerobic threshold (LT2) — so that the lactate level stays rather high and quite painful, but doesn’t spike. Theoretically, you can stay around an hour in that zone after which point you’ll be so physically and mentally (painfully) exhausted that you won’t be able to continue the effort.

The power you can produce for an hour in zone 4 is called functional threshold power, or FTP. It is possible to determine it by making an FTP-test using a standard 20-minute protocol or a more progressive 2×8 minutes. Also, current training platforms use algorithms to establish FTP based on shorter efforts — which may or may not work accurately enough for you.

Note that power, not heart rate or any other metric, is in fact central. After all, the more power you generate, the faster you go (minus the resistance forces) — and at what frequency your heart rate beats at that, is just a byproduct, not the actual factor affecting your forward movement.

While there exist methods of measuring running power, the only really accurate and predictable way is measuring the power at a mechanical point, such as a pedal, crankset, or wheel. This is the first big reason why cycling is best for zone-based training — you can actually measure the zone you’re in, not guesstimate it.

Your power levels and their relation to the intensity zones are quite stable in time — they’ll shift with the increase in your training level, but there is no in-the-moment randomness of heart rate.

To be complete on the topic, runners can use pace as a metric for establishing zones. While it is more predictable than with cycling, it’s still not always accurate — as the pace/speed is affected by resistance forces such as gravity (if you move even slightly uphill), aerodynamics (if there’s wind — that affects runners too) & ground resistance (rolling for cyclists and hysteresis for runners — think of pushing through dry sand or mud).

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

C) By lactate level

By now we know that the central zone 4 is determined by the lactate level (or rather the rate of its increase). Now let’s take a look at zone 3. While it obviously ends where zone 4 starts — so, close to the anaerobic threshold (LT2) — the start of zone 3 is called aerobic threshold (or LT1), which also is based on lactate.

It is considered that the aerobic threshold (LT1) is hit when the concentration of lactate increases above 2 mmol per liter of blood. Physiologically, this means that the rate of lactate generation has overcome the capacity of the body to fully process it — before the aerobic threshold (LT1) the body keeps lactate level steadily low (in theory, infinitely), and after that, it gradually increases.

If you spend enough time in zone 3 — we talk several hours — again, the lactate level will overcome your body’s capability to deal with it, and you’ll shut down (in a hell of a pain by that moment — so much so that in practice you’ll ease-off voluntarily way before that).

Training in zone 3 is most relevant if you do events such as full ironman — a longer competitive effort separated in time from other hard efforts (unlike stage racing in pure cycling) and individual in nature (unlike group dynamics/tactics in pure cycling). In such individual events the majority of your effort shall be in zone 3 for the best result.

As to the measuring of lactate, in the past it has been quite impractical for the real outdoor scenarios — as that required piercing your finger with a lancet and taking blood samples — suitable only for rare indoor tests, not even periodic training.

Such tests, if done right, allow for accurately determining your current power levels (and, to a certain degree, heart rates — subject to the above reservations) at LT1 and LT2 (more precisely than FTP test), which is enough to do from time to time and then rely on your power meter for zone separation.

That said, the current technology already allows for constant lactate monitoring via wearable devices similar to continuous glucose monitors that pierce your skin while being temporarily glued to it around the puncture — this is good news for sports other than cycling, as measuring zones becomes much more precise with it.

This still leaves relevant the second, even bigger, reason why cycling is best for zone-based training, but I’ll get back to it really soon.

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

D) By perceived exertion

As we determined, the upper boundary of zone 2 is where you can continue at the same effort, theoretically, indefinitely. In practice, muscle fatigue will still build up — that’s why starting your training in zone 2 should feel almost too easy, while closer to the end of a several-hour session, it gets rather hard.

That makes the traditional rate of perceived exertion (RPE) 10-step scale a tricky thing that’s unreliable if you don’t have a lot of experience in reading your body signals across longer periods of time and various effort levels. Thus, I see this method as outdated in our time of lactate monitors, power meters and, at least, heart rate sensors. Some can do it “by ear” but better use more accurate methods.

That said, subjectively perceived exertion method works better for upper zones: the harder it is, the clearer it is for you that it’s hard. However, as we can see from the description of the training methods in the very beginning of this post, almost all of them rely heavily on low-intensity training.

That’s where we should divide between zones 1 and 2. There is no clear separation point — but a distinctive difference in a training approach. Zone 2 is the basis for everything for good reasons:

• it allows training as hard as possible for extended periods of time, thus maintaining large volumes of effective training without overtraining or burning out,

• the endurance built in zone 2 is the basis for increasing your FTP and VO2 max — you need to do it by training those zones separately — but without said basis you can’t do that at all,

• it is considered that your heart muscle is the most flexible at this intensity, which means it produces the largest volume stroke here; hence, the cardiovascular training is the most effective and efficient in zone 2, as the stroke volume is the only thing that is trainable in a heart (unlike the max heart rate) and practically determines your VO2 max as statistically the narrowest link in the chain of factors establishing it.

First of all, from those reasons it’s clear that it doesn’t really matter where the boundary between zone 1 and 2 is — you should stay closer to the upper end of zone 2 when training in it. (And training in zone 1 makes almost no sense — you’ll just increase fatigue without real training benefit — that’s why it’s called recovery, as it’s suitable for active recovery for an hour or so, a day after a hard effort, nothing more.)

So, the second big reason why cycling is best for zone-based training is that cyclists can actually spend many hours at a time in zone 2 — and maintain training volumes of tens of hours per week without fatigue injuries in running or just the ridiculousness of, say, swimming for that long.

The below graph is for a 6-zone model — and with an emphasis on a somewhat controversial sweet-spot training method, so take it with a grain of salt. However, the idea of aiming at a good balance between training effect and maximum duration is relevant — just note that unlike this graph intended for runners, for cycling the maximum duration in zone 2 is way more than zone 3.

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

E) By breathing/talking test

When training in zone 2, you should also avoid overreaching into zone 3 — the risk of overtraining and a potential burn-out far outweighs possible benefits unless you are preparing, as noted above, for a specific event at a particular time (read “triathlon competition”).

That’s where such a simple thing as a talking test becomes surprisingly effective. In zone 2 you should breathe freely and be able to talk in full sentences. If you are on the phone, you should be able to speak in a way that the person on the other end could not tell that you’re exercising. (And, hey, that’s actually easier than most people think zone 2 is :)

As soon as you need to take deeper breaths between phrases, when you start chopping your sentences and changing the steady rhythm of your speech — you’re in zone 3. And that’s how you can easily separate between those zones without any sensors.

MINIMAP | Methods — Zones — By HR — Power — Lactate — Exertion — Talking — Sprinting

F) By sprinting

By now, we have established the boundaries of zones 1, 2, 3, & 4. What’s left is the upper border of zone 5 and the beginning of zone 7 (with zone 6, obviously, being in between them).

The separation point between zone 5 (VO2 max) and zone 6 (anaerobic capacity) is when your body cannot produce any more ATP (the fuel for power production) and can only rely on what’s already stored in the muscles — enough for a sprint burst of 30 seconds to a couple of minutes max.

Zone 7 (neuromuscular power) starts where the rapid depletion of the ATP stored in the muscles gets also supported by the full utilisation of phosphocreatine — not delving into the chemistry of it, that’s something that can last for up to 15 seconds of an explosive power outburst.

The difference between zones 6 and 7 is chemical/physiological — but unless you are focused on competitive sprint training, there’s not much difference. Just give it all you have for half-a-minute and you’ll touch both of them just fine. But avoid even the slightest hint of pacing yourself — try to break those cranks.

Zone 5 you can determine as harder than threshold, but still being able to maintain it for several minutes (2 to 8). Another way of identifying zone 5 accurately enough is it’s close to your max heart rate — that’s where you should be from time to time to increase your VO2 max.

Why it is super-important to do that for anyone and everyone — read in one of my previous posts on the matter (search for “VO2 max” in its title).