What Are Training Zones? How to Calculate & Use Them

Training zones are just intensity “categories” defined by how hard you are training. They range from very easy “active recovery” to all-out max effort.

They are there to help you exercise at the right intensity for the session. In this article, we’ll go through what training zones are, how many exist, what each one does to your body, how to estimate your unique training zones, and how to use them.

This article is from the Exercise section of our Library.

What Are Training Zones?

Training zones are a range of intensities that are typically expressed as a % of your max, either heart rate (HRmax) or VO2max. These aren’t just random or arbitrary values; they represent unique physiological states your body enters when you exercise.

They are based on what "fuel" you’re using (fat or carbohydrate?), how much oxygen and what byproducts your body is producing (like lactate and carbon dioxide) to produce energy.

This is important because training at different intensities triggers different adaptations. So the idea is that, as not all exercise is the same, doing the right type of training, at the right time, will produce better results rather than training randomly.

How Many Training Zones Are There?

This is confusing, as there are no universally agreed-upon standards. There are 2, 3, 4, 5, 6 and 7 zone models [1].

But we think the 3 or 4-zone models are the best ones, because each zone is bordered by distinct and measurable "physiological boundaries” that are split by three well-established “physiological thresholds”.

This means each zone represents a unique physiological state that is personalised to your own physiology — they are not based on arbitrary boundaries based on % estimates.

1. First Metabolic Threshold (MT1)

Takes many names, which are all calculated or measured slightly differently but all very similar (e.g., aerobic threshold (AT1), ventilatory threshold (VT1), lactate threshold (LT1)).

2. Second Metabolic Threshold (MT2)

Also known as the anaerobic threshold (AT2), second lactate threshold (LT2), maximal lactate steady state (MLSS), second ventilatory threshold (VT2), respiratory compensation point (RCP) or critical speed (CS) or power (CP) threshold.

3. VO2max

The maximum amount of oxygen your body can use. Any intensity above this threshold is purely anaerobic (without oxygen).

3 Zone vs. 4 Zone Model

The model we use is essentially the same standard 3-zone model that has been used for decades [2]. The extra zone (“zone 4”) we’ve added is used to plan and prescribe high-intensity training using your pace or power outputs (not based on your heart rate).

Traditionally, zone 4 workouts like high-intensity interval training (HIIT), sprint and speed training haven't been used by endurance athletes. But they are now fairly common and are beneficial for endurance performance.

In practice, you can just stick with a simple 3-zone model and call zone 4 "above zone 3", which is semantics really. But, because there's a range of paces or power outputs above zone 3, we think it is more accurate to call it a "zone".

So, zone 4 starts from the pace or power at your VO2max and ends with your all-out 100% max or peak pace or power (as fast and hard as you can run, swim or pedal: it's a sprint).

At the start of zone 4, you are at (or very close to) your HRmax. This means that even if you increase your pace or power output while in zone 4, there will be no further increase in your heart rate (or VO2).

Put simply, if you're using heart rate to estimate, prescribe or monitor your training intensity, there are basically 3 zones (zones 1-3). If you're estimating, prescribing or monitoring off your pace or power output, above your VO2max, there's an extra zone (zone 4).

Other Training Zone Models

The 5-zone training model is popular, being the same as our 4-zone model, only with zone 1 being split into two by an arbitrary value (usually 50-60% HRmax or VO2max).

In the 5-zone model, "zone 1" is below the arbitrary value (say 60% HRmax) and "zone 2" sits above it but below MT1. The extra zone in the 5-zone mode ("zone 1") is used to prescribe active recovery.

There is also a six and "7-zone" models, where zone 5 in the 5-zone model, or zone 4 in our 4-zone model (i.e., all intensities above VO2max), is split into two or three more zones: intensities around VO2max (zone 5), all-out 100% max (zone 7), and then another zone in between (zone 6) defined by when you muscles stop producing lactate (called "vLamax").

The "4-Zone" Training Model

Zone	Thresholds	%HRmax	%VO2max	% 30 min Pace	Effort (1-10)
1 – Light	< MT2	<75	<65	<80	<4
2 –Moderate	MT1–MT2	75–85	65–85	80–100	4–6
3 – High	MT2–VO2max	85-100	85–100	100-120	7–9
4 – Very High	>VO2max	100	100	>120	>9

What's Happening in Each Zone?

Zone 1 — Low or Light Intensity

At this intensity, your aerobic system is active but not working hard. Blood flow increases gently, oxygen demand is low, and your muscles rely almost entirely on fat. This zone promotes recovery without stressing the body.

Zone 2 — Moderate Intensity

The end of zone 1 and into zone 2 is arguably the most important intensity for long-term cardiovascular health and endurance performance. This is where endurance athletes will spend a lot of their time training.

Towards the middle of zone 2 (and going into zone 3), exercise starts to get hard, being at around your "race pace". Training in this zone will improve performance, but it will also take longer to recover from.

So, some coaches don’t like training too much at this intensity, as more efficient performance improvements can be achieved at higher intensities. This is a widely debated topic in the sports science community with opinions on both sides.

Zone 3 — High Intensity

This is where you are pushing close to your ceiling. Your heart, lungs and muscles are working hard. You’ll get some of the most efficient stamina improvements (i.e., per minute of exercise). Time spent at this intensity is typically brief (under 20 minutes total) and requires full recovery between sessions.

Zone 4 — Very High

This is near all-out, maximal efforts which last seconds. The predominant energy source for this exercise intensity is not powered by oxygen — you’re using other reserves in your body. These sessions need the longest recovery and are used to improve power output, VO2max and anaerobic capacity.

Terminology Explained

Aerobic vs Anaerobic Exercise

Aerobic exercise literally means 'with oxygen.' Your muscles use oxygen to convert fat and carbohydrates into energy — in a sustainable, efficient process. Zones 1 and 2 are primarily aerobic.

Anaerobic exercise is when intensity increases past the point where you can use oxygen to generate energy quickly enough.

At this point, your muscles turn to other (less efficient) ways to produce energy. These energy pathways produce a by-product called lactate: this is what predominately happens in zone 3 and zone 4.

“Zone 2 Training”

“Zone 2” has become one of the most talked-about training zones. In the 3 and 4-zone training models, it sits at the end of zone 1 (confusingly) — just below MT1.

It’s a pace where you can hold a conversation easily, you burn the most fat, you can maintain it for well over an hour, and you’ll get fitter training in this zone.

It’s an efficient zone for training your stamina. Most endurance athletes will spend 80% of their total weekly training in zone 1 and zone 2 [2].

Lactate Threshold

This is where a byproduct (lactate) starts to accumulate in your body, rising above resting levels. This is what differentiates zone 1 (no lactate accumulating) and zone 2 (blood lactate increases).

It also splits zone 2 and zone 3 (where lactate starts to increase regularly, going up every time you measure it). When training in zone 3, you’ll start to feel more fatigue as more time passes.

Zone 3 exercise is "unstable" because your underlying physiology is continually changing as you get more and more tired when training in this zone. Your heart rate, breathing rate, VO2, lactate, body temperature and feelings of fatigue aren't stable; they'll keep drifting up in zone 3.

The key to improving your race performance is to increase your pace and power outputs at which lactate starts accumulating. However, this doesn't mean you have to always train at these threshold intensities (zone 2). In fact, some coaches advise avoiding them!

Polarised Training (80/20)

This is where ~80% of sessions are spent in zone 1 and ~20% in zones 3 and 4, with little time spent in zone 2. Basically, they train at very high or very low intensity, with little moderate intensity training.

Some researchers (not all!) have suggested this is more efficient and effective for improving stamina and endurance [3]. Athletes from a lot of different sports tend to gravitate to this type of training naturally.

“FatMax”

This is the intensity at which your body burns the most fat [4]. It typically occurs in zone 1 or zone 2. Note, your Fatmax is not the same as burning the most calories (that’s in zone 4, more intensity means more calories burned per minute).

Your diet, fitness level, hormones, health, and what and when you last ate can shift your FatMax intensity higher or lower.

How to Calculate Your Training Zones at Home

The gold-standard way to know your training zones is to get an exercise physiologist to test you in a lab. However, there are also some field tests you can do yourself.

Use your Heart Rate

Calculate your maximum heart rate (208 − (age in years × 0.7)) and use the % of this to estimate what exercise intensity you should exercise at. You’ll probably need a heart rate monitor or something that can estimate your heart rate whilst you exercise.

So for a 29-year-old, your training zones would be: under140 bpm (zone 1), 140–159 bpm (zone 2), 159–187 bpm (zone 3) and over 187 bpm (zone 4).

Maybe you can see what the problem is with this method (not all 29-year-olds will have the same training zones). So it’s only really used for beginners or as an educated guess if you don’t know anything about your training capacity.

Talk Test

This is easy and one that coaches and athletes love to use. You should be able to hold an easy conversation in zone 1. It will be difficult but possible to hold a conversation in zone 2. And in zone 3, you can’t talk and need to concentrate on getting enough oxygen into your body. It’s not the most accurate, but it’s practical.

Exercise Test

Some runners just use simple rules to plan their training, like marathon pace (zone 1), 10 K pace (zone 2) and 3 K pace (zone 3).

The fastest pace that you can hold and sustain for 30 minutes is also a good way to estimate your MT2 (zone 2 to going into zone 3). You can then use your average pace, power output or heart rate (last 20 minutes of the test) to estimate your training zone intensities from the table above.

So if your average heart rate over the final 20 minutes of the test was 168 bpm (~85% HRmax), your zones would approximately be: under 148 (zone 1), 148–168 (zone 2), 168–197 (zone 3).

If you ran 3 miles in 30 minutes (6 mph, 9.5 kph, or 10 min/mile pace), your zones would be: under 12.5 min/mile (zone 1), 12.5–10 min/mile (zone 2), 10–8.3 min/mile (zone 3), over 8.3 min/mile pace (zone 4).

How to Use Training Zones

Workout Type	Effort	Example Workout
"Aerobic Base"	Light	60 min at 70% HRmax
"Tempo"	Moderate	30 min at 80% HRmax
"HIIT"	Very Hard	4 × 4 min ~HRmax with 4 min recovery at 60% HRmax
"Polarised"	Mixed	20 min at 60% HRmax 6 × 3 min at ~HRmax with 3 min recovery at 60% HRmax.
"Fatmax"	Light	90 min at 60% HRmax fasted
Threshold	Hard	3×8 min at 90% HRmax with 5 min recovery 60% HRmax

Here’s an example of how you can use training zones to target specific adaptations or goals for a typical week of training using a 4-zone model.

All you have to do is calculate your specific training zone intensities to adapt the workout to your fitness level. Beginners will need more rest, so only select 2–3 sessions to do for the week. Don't forget warmups and cooldowns for the training sessions.

Day	Goal	Example Workout
Monday	Improve MTs	45 min in Zone 2
Tuesday	Improve VO2max	4 × 4 min in Zone 4 4 min recovery in Zone 1
Wednesday	Active Recovery	30 min in Zone 1
Thursday	Improve MTs	20 min in Zone 2, then 10 min in Zone 3
Friday	Active Recovery	30 min in Zone 1
Saturday	Aerobic Base	90 min in Zone 1
Sunday	Recovery	Mobility + Complete Rest

Important Notes: The Limits of Zone Prescriptions

The only way to accurately calculate your zones is to get your two metabolic thresholds and VO2max measured.

So, any zone that is based on percentages is just a guide, not gospel. They aren’t 100% accurate, somewhat arbitrary, even if they are clinically measured in a lab [5].

Individual variation

Fixed intensity range estimates do not produce identical metabolic responses across different people. The only way to do this accurately is to have your thresholds tested in a lab.

Cardiac drift

In hot conditions or during longer sessions, your heart rate rises for the same effort level — a phenomenon called “cardiac drift”. Use your perceived effort to double-check this.

Medication

Beta-blockers and some other medications suppress heart rate response, rendering %HRmax zones unreliable. Use perceived effort (out of 10) instead.

Day-to-day vibes

Sleep deprivation, illness, stress, fatigue and poor nutrition all affect your heart rate, perceived effort or performance thresholds. Use zones as a framework, not a rigid prescription, and always factor in how you feel.

The Takeaways

Training zones can transform vague or poorly planned effort-based sessions into structured, periodised, and purposeful programmes.

The four-zone model here gives you intensity prescriptions for when you want to go easy or active recovery (bottom of zone 1), fat burning and aerobic base (top of zone 1 into zone 2), want to improve thresholds and exercise efficiency (zone 2 and 3), or max-out and increase speed (zone 4).

For most athletes, zones 1 and 2 are the bread-and-butter day-to-day training [6]. Zones 3 and 4 are targeted tools used intermittently and strategically for specific purposes.

You can estimate your personal zones with a 30-minute time trial if you can access a professional test. Reassess it every 8 to 12 weeks as your fitness improves. Let your own physiology dictate your sessions rather than following someone else’s programme.

Sources

1. Bishop DJ, et al. Physical Activity and Exercise Intensity Terminology: A Joint ACSM Expert Statement and ESSA Consensus Statement. Med Sci Sports Exerc. 2025;57(11):2599-2613. PMID: 41085254

2. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform. 2010 Sep;5(3):276-91. PMID: 20861519

3. Stöggl T, Sperlich B. Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. Front Physiol. 2014;5:33. PMID: 24550842

4. Achten J, Jeukendrup AE. Optimizing fat oxidation through exercise and diet. Nutrition. 2004;20(7-8):716-727. PMID: 15212756

5. Jamnick NA et al. An Examination and Critique of Current Methods to Determine Exercise Intensity. Sports Med. 2020 Oct;50(10):1729-1756. PMID: 32729096

6. Esteve-Lanao J et al. How do endurance runners actually train? Relationship with competition performance. Med Sci Sports Exerc. 2005 Mar;37(3):496-504. PMID: 15741850