What Do the 5 Training Zones Stand For? — Zone 2 in the Spotlight

As you may have guessed, there are other training zones besides zone 2, to be more specific, five in total.

The five training zones are a concept in endurance training that classify the intensity of training, dividing it into different zones depending on your heart rate. Each zone represents a certain percentage of the maximum heart rate or Functional Threshold Power (FTP).

Your maximum heart rate, also called maximum pulse or Max HR, is the highest rate your heart can reach under exercise. Functional threshold power is an important term in cycling and endurance training. It is the maximum power that an athlete can maintain before they enter anaerobic metabolism and fatigue sets in.

So, how do these zones work?

The Five Zone System of Heart Rate Training

Heart rate zone training refers to training in different heart rate zones that vary in terms of the intensity of the workout and how energy is provided to the body.

These zones are related to anaerobic and aerobic metabolism.

Aerobic Zone

The aerobic zone is the area where your body can provide enough oxygen to supply the energy needed for activity. This is usually the case at lower to moderate intensity.

The heart rate target in these zones is typically between 60 and 80% of your maximum heart rate. This is where your body mainly burns fat for energy.

Anaerobic Zone

In the anaerobic zone, you train at higher intensities where your body cannot provide enough oxygen to meet energy demands. Your heart rate in these zones is typically above 80% of your maximum heart rate.

In the anaerobic zone, your body relies more on burning carbohydrates because they provide energy faster, but they also produce more lactic acid.

Dividing your training into the different heart rate zones makes it easier for you to control your training intensities. The zones also each have different training goals and health benefits.

The term “blood lactate levels” does not really ring a bell? No problem.

Blood lactate level, also referred to as blood lactate concentration or lactate value, is the amount of lactate (lactic acid) present in a person's bloodstream.

Lactate is a metabolic product formed during energy production in your body, especially during anaerobic activities where oxygen demand exceeds oxygen supply. The more intense your training is, the higher the maximum heart rate and lactate level in your body. The higher a training zone is, the less time you can spend in it.

You can think of the different zones in endurance training as being similar to the different numbers of repetitions in strength training. Low weights and many repetitions are like zone 1, while high weights and few repetitions are comparable to zone 5.

Below, we have listed the five zones and described them in more detail.

Zone 1 – Recovery and Regeneration

This is the lowest intensity zone (low-intensity training) in endurance training. Training in Zone 1 is mainly for recovery and regeneration. The maximum heart rate in this zone is 50-60%.

In this zone, you can train for a long time until you get tired.

Maximum heart rate: 50-60 %

Blood lactate level: 0-1.5 mmol/L

Main goal: recovery and regeneration

Zone 2 – Light Endurance Training & Aerobic Fitness

Zone 2 cardio, the star of this article, is a relatively light form of aerobic and base fitness training. However, even this training can be strenuous due to the longer duration of the training. Well-trained athletes are able to complete more intense workouts with a maximum Zone 2 heart rate of 70%.

The lactate level in zone 2 cardio is low, below 2.5 mmol/L. This means that your energy production is aerobic. The energy you need is derived 80-90% from fat. This makes zone 2 training quite popular for people wishing to lose weight and fine-tune their bodies in the long term.

During zone 2 cardio, you can still have relaxed conversations, which makes it an excellent training method that can be exercised with friends or socially.

If you train regularly in zone 2, you will improve your body's ability to use fat as an energy source and increase your aerobic endurance.

Maximum heart rate: 60-70%

Blood lactate level: 1.5-2.5 mmol/L

Main goal: increase aerobic capacity and fat burning. [1]

Zone 3 – The Aerobic Zone

Fitter, faster, and thinner – these are the advantages that have been associated with Zone 3 training for decades and made “aerobic fitness” so popular, besides Jane Fonda. As you might have noticed, aerobic fitness can fall into zones 2 and 3, whereas in zone 2, we speak of aerobic fitness, and zone 3 predominantly targets aerobic fitness endurance.

In the third zone, you train your aerobic and anaerobic threshold. Zone 3 is ideal for longer workouts where you maintain a moderate pace. At this intensity, you need to concentrate, and you will be challenged.

You can sustain the training sessions in Zone 3 for about an hour. As you increase the intensity of your workouts and enter the third zone, cellular byproducts (lactate) begin to accumulate, and a different energy production process begins.

Maximum heart rate: 70-80%

Blood lactate level: 2.5-4.0 mmol/L

Main goal: increase in aerobic and anaerobic thresholds

Zone 4 – Increase Anaerobic Endurance

Training in zone 4 is strenuous, and you can only maintain it for a certain amount of time. Training in this zone helps improve the body's ability to process lactate more efficiently and increase anaerobic endurance.

Maximum heart rate: 80-90%

Blood lactate level: 4-8 mmol/L

Main goal: Increase lactate threshold and anaerobic capacity.

Zone 5 – High-Intensity Training Intervals

Zone 5 is used for short, high-intensity intervals to increase maximal power and speed. It is very strenuous and the highest heart rate training zone.

You are at the maximum of your capacity in Zone 5, and you can't maintain that intensity for long. It's like a classic high-intensity workout where your heart rate is very high or at its maximum.

Maximum heart rate: 90-100%

Blood lactate level: 8-12 mmol/L

Main goal: increase maximum power and speed

And how can you make this heart rate zone training work for you and train in the suitable zones?

The exact percentages of maximum heart rate or functional threshold power vary depending on individual factors.

Therefore, it's best to get advice from a professional, like a personal trainer, or use special training equipment that allows you to measure your heart rate. An Apple Watch or another fitness tracker can also be helpful with this.

But now, let’s get back to the real focus of this article – why is zone 2 cardio so popular?

Why is Zone 2 Cardio So Popular?

The main goal of zone 2 cardio is to build and develop good foundational endurance and improve fitness.

Zone 2 cardio usually consists of long endurance sessions. It is especially suitable for beginners and for preparing for more intense sports sessions. Interestingly enough, many professionals in cycling, rowing, swimming, or running train up to 80% in zone 2 and only the remaining time in the higher zones. [2]

“Training in the lower zone leads to good results in endurance sports,” says, for example, Dr. Mike T. Nelson, owner of Extreme Human Performance.

Zone 2 as an Easy Introduction to Endurance Sports

Zone 2 cardio offers you an easy introduction to endurance sports that won't overwhelm you.

It is suitable for beginners as well as advanced exercisers because it is not too strenuous. The training is effective, and you do not need long recovery times.

In addition, you can make sustainable progress with zone 2 cardio and lay a good foundation for more intense workouts because you improve your fat metabolism and oxygen transport . It is a very gentle form of training for people with little experience in sports. [1]

Zone 2 Prepares You For Intense Workouts

Zone 2 cardio is ideal for preparing your body for more intense workouts because it's low intensity but still increases your endurance. Typical Zone 2 exercises are steady and long runs, cycling, swimming, and rowing. Even a hike can be exercised in Zone 2.

For running or cross-training, for example, your body is in a range of about 60 to 70 percent of your maximum heart rate. Initially, your running pace is low, but over time, you can maintain this heart rate at higher speeds.

If you stay in the heart rate range mentioned, you can reap the benefits of this zone. We’ll get to those benefits in the next section.

Zone 2 is also a good preparation for more intense forms of training like High Intensive Interval Training (HIIT).

By the way, you can also use zone 2 cardio very well for recovery after intense sessions. [3]

After all, Zone 2 cardio is so popular because of its many health benefits, which you'll learn about in the following chapter.

What Are the Health Benefits of Zone 2 Cardio?

Not only can you increase your endurance and fitness with zone 2 cardio, but you can also improve your overall health. That's because, with this low-intensity workout, you'll improve your cardiovascular health, fat-burning, and metabolism, as well as the condition of your mitochondria. [4] [5] [6] [7]

As a result, you'll reduce your risk for well-known lifestyle diseases (type-2 diabetes, coronary artery disease, etc.). All this can contribute to a longer, healthier life. [6]

Endurance – Zone 2 Cardio Helps You Run That Marathon

Do you finally want to run that marathon? Since you're at about 60 to 70 percent of your maximum heart rate during zone 2 cardio, you can sustain longer workouts of one to two hours. This workout will improve your base endurance and your fat burning at the same time.

As a beginner, you'll set the foundation for your endurance ability with Zone 2 cardio, while experienced endurance athletes can further improve their aerobic fitness in this zone.

Whether you run, weight train, cycle, or row, good endurance is the foundation of your athletic performance.

With endurance training, you improve your oxygen supply and your VO2 Max, which has a significant impact on your performance. With a good endurance capacity, you can endure steady training sessions longer and regenerate faster. [4]

Fat Burning – Zone 2 Cardio For Losing Weight

In this moderate-intensity zone, the body uses fat as the primary source of energy (80-90%). This promotes long-term fat burning and efficient use of fat as an energy source. Carbohydrates are saved for phases of higher performance.

This optimizes your energy supply during training. Furthermore, you have a good calorie consumption with relatively low effort in Zone 2.

Although you burn fewer calories during endurance training compared to intense sessions, you can train much longer without getting exhausted. Thus, you can improve your body composition with zone 2 cardio, and fine-tune your body. [5]

Cardiovascular Health – Zone 2 For a Strong Heart

Zone 2 cardio also helps improve cardiovascular health by stimulating the heart to work more efficiently and pump more blood into circulation. Through regular cardio exercise, you'll not only strengthen your heart, but you'll also improve blood flow and, along with it, oxygen and nutrient delivery.

The moderate intensity of Zone 2 cardio helps regulate your blood pressure and lower your resting heart rate. In this way, you can reduce the risk of developing cardiovascular diseases which can result in heart attacks or strokes. After all, an unhealthy lifestyle and lack of exercise are among the biggest risk factors. [6]

Healthier Mitochondria For Improved Athletic Performance

Mitochondria are the powerhouses of your cell and play an important role in your athletic performance. They produce your muscles' fuel, adenosine triphosphate, shortly referred to as ATP.

By training, you can increase the number of your cellular power plants, the mitochondria, which decrease naturally with age. Zone 2 cardio also improves the mitochondria's ability to build new cells and break down old cells.

Thus, zone 2 cardio also affects your longevity and your health as you grow older. Improperly functioning mitochondria are associated with various diseases, such as cardiovascular disease, cancer, diabetes, and obesity. So, with zone 2 cardio, you can rev up your “engine.” [7]

Furthermore, moderate exercise, ideally outdoors in the fresh air, has numerous other positive effects on your health. Exercise can have a positive effect on your mood, promote sleep, counteract high blood pressure, and strengthen your memory.

So it's well worth incorporating more movement into your daily routine and exercising regularly in Zone 2.

How Much Zone 2 Should I Include in My Training Plan?

In your training plan, you should train about 60-80% in Zone 2 and 20-40% in more intense zones, depending on your goals, current fitness level, and individual circumstances like health conditions. With this training, you will improve your endurance and your body's ability to use oxygen efficiently.

To train in Zone 2, you can run, cycle, hike, swim, or even row down your local river. You can exercise your workouts in nature or in gyms.

Whilst training in nature can be relaxing and improve mental wellness, at the gym, you have the advantage of being able to work out in any weather and diversify your workout by alternating between the rowing machine, bike, and treadmill. To determine if you are training in Zone 2, it is best to pay attention to your breathing. You should be able to breathe through your nose and carry on a conversation despite your workout if you train in Zone 2.

Dr. Peter Attia, an expert in the field of longevity, recommends exercising in Zone 2 for at least three hours per week. In this video, Peter Attia discusses with Iñigo San-Millán how often you should exercise in Zone 2.

However, there is debate about how much time you should spend in Zone 2 to get the best results. For example, if you do a lot of sitting in your daily life because you have a desk job, any form of low-intensity exercise will help.

If you are already quite fit, it is recommended to exercise in Zone 2 twice a week for at least 30–40 minutes. Endurance athletes typically spend around 80% of their training in Zone 2. [7]

Mike T. Nelson, owner of Extreme Human Performance, recommends aerobic workouts three times a week. For those who place more emphasis on strength and want to build body mass or lean muscle mass, he advises at least 20 to 30 minutes per day. This is sufficient for the average person to benefit from some of the aerobic adaptations mentioned. [8] You can listen to or watch more from Mike Nelson here.

Dr. Kerry Stephen Seiler, Professor of Sports Science at the University of Agder, Norway, has conducted several studies on endurance sports and exercise physiology. His research highlights the benefits of training in Zone 2 and points to an optimal distribution of intensity. His results further emphasize the importance of low-intensity training for endurance, health, and overall fitness. [9]

Learn how you can train like the best endurance athletes as a “normal person” in this TED Talk with Stephen Seiler.

How Do I Determine My (Maximum) Heart Rate?

The training heart rate, i.e., the frequency at which your heart beats per minute, has become more and more important in mainstream fitness recently. It is an important measure of training intensity. Many athletes measure their heart rate during a workout. The reason for this is that it allows you to measure your athletic load and optimize your training.

The heart rate at rest is usually a value of 60–80 beats per minute. During exercise, your heart beats faster, and therefore, your heart rate is higher. In addition, your heart rate depends on your age, weight, height, and current training status.

In order to determine your maximum heart range, a performance diagnosis by professionals is necessary. To do this, you must run fast on the treadmill, for example, until you experience a significant drop in performance. At this point, the measured pulse corresponds to your maximum heart rate.

However, you can also use formulas to calculate your maximum heart rate. For example, you can use this rule of thumb as a rough guide:

Maximum heart rate = 220 – Age

To calculate your maximum heart rate, you can also use the more accurate Sally Edwards formula as a guide:

Men: Maximum heart rate = 214 – 0.5 × age – 0.11 × body weight in kg

Women: Maximum heart rate = 210 – 0.5 × age – 0.11 × body weight in kg

For men, the maximum heart rate is calculated by subtracting from the base value 214, on the one hand, half of the age in years and 0.11 times the body weight in kilograms. For women, the same formula applies, but with a basic value of 210.

Let's illustrate this a little better with an example:

A 25-year-old woman weighing 60 kilograms reaches a maximum heart rate of about 190 beats per minute at most. A man of the same age and weight, on the other hand, can expect a maximum heart rate of about 195 beats per minute. [10]

Another possibility, which is especially aimed at healthy and well-trained athletes, is the method, according to Winfried Spanau:

Men: maximum heart rate = 223 – 0.9 × age.

Women: maximum heart rate = 226 – 0.9 × age

Alternatively, you can simply use this online calculator from Berg-Freunde:

The maximum heart rate, according to Edwards, is 190 beats per minute for the average person and 196 beats per minute for trained athletes, according to Spanaus. These values naturally vary from person to person.

You can also measure your heart rate with different fitness trackers or smartwatches like an Apple Watch. In gyms, you usually have the possibility to measure your heart rate on the endurance machines as well. [11]

What Are Potential Problems With Dividing Training Into Zones?

“Zoning” your workouts can be a useful way to manage the intensity of your workouts and ensure that you meet your training goals.

However, there are also some potential problems and challenges with this practice:

Individual Differences in Training Zones

Each person is unique, and training zones can vary from person to person. Using general formulas to determine training zones does not take into account individual differences in fitness, physical condition, and individual heart rates.

This may result in zones that are not optimal for some individuals because they may be different for you personally. What might be a Zone 2 for one person might not be a Zone 2 for another person.

Therefore, in addition to the training zones, you should consider your individual training goals and needs. Tailor your training program to your specific goals, your current level of performance, and your body.

Accuracy of Maximum Heart Rate Calculation

Calculating maximum heart rate is often based on formulas such as "220 minus age" for a rough estimate.

However, these formulas are not always accurate and can lead to incorrect training zones, especially for older people or athletes with specific medical conditions.

Monitoring Progress With Zone 2 Training

In order to be always aware of your current state of fitness and your progress, you would need to perform a performance test on a regular basis.

Based on these performance tests, you decide how intensive your training should be. As you improve through regular training, you should adjust your training sessions accordingly to continue to improve your performance.

You can get inspiration and guidance on your performance from CARE or assess it yourself with this guide from the Dr. Holzinger Institute.

When measuring your progress, consider other factors besides heart rate, such as speed, strength, and endurance. We will briefly go into these factors in a little more detail:

Consideration of Daily Form and Environmental Factors

Your heart rate can vary from day to day and even from workout session to workout session due to factors such as sleep, diet, stress, and environmental factors.

Therefore, classifying workouts into different training zones based on heart rate is not always reliable. Take into consideration how you feel, how you slept, and if there are any environmental factors that might disrupt your usual training pattern like the weather.

Overemphasizing the Five Zone System

Some athletes may tend to focus too much on adhering to certain zones, neglecting to consider other important training factors such as proper technique, workout duration, and frequency of training units.

Despite these challenges, dividing your training into the five-zone system of heart rates can be a useful way to manage training intensity and serve as a guide for sustainable endurance training.

However, it is important to consider individual differences and the full range of training factors to ensure effective and safe training. A personalized approach that takes into account your individual fitness and goals is the best strategy to optimize your health, fitness, and endurance over the long term.