Zone 2 Training: Build Your Aerobic Capacity + Improve Performance

Our running coach Amber Sayer gives us the science on Zone 2 training and its benefits.

Many runners assume you have to train fast to get faster, and while speedwork is an essential component of becoming a faster runner, it’s equally important to build your aerobic base with easy running.

That’s right—you actually have to run slow to run fast.

Heart rate zones denote different effort levels or exercise intensities, ranging from zone 1—very light effort—to zone 5, all-out, maximal intensity. Zone 2 training should be integral to any distance runner’s workout program. 

Ready to train like an elite runner and smash your PRs? Keep reading for our complete guide to the science and benefits of Zone 2 training so you can work it into your training plan.

A person looking at their running watch.

What Is Zone 2 Training?

In recent years, there has been a surge in interest in the benefits of Zone 2 training. Inspired partly by the achievements of Tour de France winner Tadej Pogačar and recent discussions on various podcasts by his trainer, Dr. Iñigo San Millán.

Nevertheless, zone 2 training isn’t just for cyclists; it is for all endurance athletes, especially runners.

Zone 2 cardio, or zone 2 training, refers to performing workouts at an intensity level that lands your heart rate in zone 2.

Heart rate zones are intensity levels stratified by specific percentages of your maximum heart rate and are measured during training with a heart rate monitor like a Garmin or Apple Watch.

Because your heart rate increases with the effort or intensity level of a workout and correlates with the percentage of your VO2 max, training by heart rate zones is a practical and feasible way to be precise and specific in quantifying effort level.

The five heart rate zones are as follows:

Heart Rate Zones

ZonePercentage of Maximum Heart RateFeels LikeTraining Goals and Uses
Zone 150-60%Very easy recovery, barely joggingComplete recovery, getting the body moving without stressing it
Zone 260-70%Easy recovery jogging, conversational pace, should be able to pass a talk test.Recovery runs, long runs, aerobic cross training, building endurance 
Zone 370-80%Challenging, but doable, sustainable for longer distance races (10k-marathon)Build up aerobic fitness, getting a challenging aerobic workout 
Zone 480-90%Uncomfortable: around 84% of your max heart rate, you hit your ventilatory threshold, so your body starts relying on anaerobic metabolism to produce energy. Tempo runs, interval training, shorter races, boosting performance 
Zone 590-100%All-out effort, like HIIT, usually only sustainable for 30-60 seconds Increasing speed, strides, finishing kick, short intervals, hill repeats, plyometrics

Related: What’s a Good VO2 Max? Average VO2 Max By Age And Sex

Zone 2 training involves running or cross-training at a pace that keeps your heart rate within 60-70% of your maximal heart rate.

At first, this low-intensity running may feel painfully slow—at times, almost impossible, particularly if you hit a hill. However, over time, your body will adapt, and you’ll be able to run faster paces while maintaining a Zone 2 heart rate. 

Even though it’s at the low end of the effort scale and can feel “too easy” to be beneficial to some runners, if you’re looking to run faster and improve your performance, you should actually be spending the bulk of your training time and mileage in your Zone 2 heart rate.

In fact, if you look at the training logs of any elite athletes or professional distance runners, you’ll find that the fastest runners are doing a significant percentage of their volume at paces that are slower than mid-pack finishers.

This is because they are capitalizing on the benefits of Zone 2 training.

A person with a calculator and a notebook.

How Do You Calculate Your Zone 2 Heart Rate?

Of course, you need to calculate your Zone 2 heart rate in order to ensure you’re actually running in Zone 2.

Zone 2 is defined by a 60-70% heart rate range of your maximum heart rate, which will be linked to your fitness level. If you already know your maximum heart rate, you can use that to calculate your Zone 2 heart rate zone; otherwise, you can estimate your maximum heart rate using the following formula:

  • Maximum Heart Rate for Males = 208.609-0.716 x age 
  • Maximum Heart Rate for Females = 209.273-0.804 x age

For example, if you’re a 36-year-old male, you would calculate your heart rate like this: 208.609-0.716 x 36 = 183 bpm.

If you’re a 36-year-old female, you would calculate your heart rate like this: 209.273-0.804 x 36 = 180 bpm.

Once you have your maximum heart rate, you need to calculate your heart rate reserve (HRR) metrics, which is your maximum heart rate minus your resting heart rate (HRR = Maximum heart rate — resting heart rate).

People running on the beach with a heart rate monitor.

Measure your resting heart rate first thing in the morning while you’re still lying in bed. For example, if your max hr is 180 bpm and your resting heart rate is 60, your heart rate reserve is 120 bpm.

From there, you can determine your zone 2 heart rate with the following formula:

  • Lower end of the heart rate range = 0.60 x HRR + resting heart rate
  • Upper end of the heart rate range = 0.70 x HRR + resting heart rate

With an HRR of 120 bpm, for example, you would end up with the following:

  • Lower end of the heart rate range = 0.60 x 120 + 60 = 132 bpm
  • Upper end of the heart rate range = 0.70 x 120 + 60 = 144 bpm

This means the runner’s Zone 2 heart rate is 132-144 bpm.

A person pointing at their training watch.

Is Zone 2 Training Too Easy?

Competitive runners may worry that spending too much time training in Zone 2 will make them slower, not faster, as the Zone 2 heart rate is so low that running at that pace is typically much slower than their race pace. 

However, research1Kenneally, M., Casado, A., & Santos-Concejero, J. (2018). The Effect of Periodization and Training Intensity Distribution on Middle- and Long-Distance Running Performance: A Systematic Review. International Journal of Sports Physiology and Performance13(9), 1114–1121. https://doi.org/10.1123/ijspp.2017-0327 shows that the most successful approach to getting faster involves what is known as polarized training—running both very slow and very fast rather than just sticking at one constant pace day in and out.

In other words, it’s more effective to vary your intensity from workout to workout rather than mindlessly lace up the sneakers and plod along at the same pace every day.

Incorporate different types of workouts into your training program to reap the benefits of low-intensity and high-intensity workouts and training sessions.

Some top endurance athletes like Rich Roll credit their peak performance and athletic success to Zone 2 training.2Lactate Testing & Training Zones – Rich Roll. (2009, July 10). https://www.richroll.com/blog/lactate-testing-training-zones/

A person running.

What Are The Benefits Of Zone 2 Heart Rate Training For Endurance Athletes?

Besides being a good way to induce polarized training and change up the stimulus and stress placed on your body, Zone 2 training for runners is beneficial for the following reasons:

#1: Reduces the Risk of Musculoskeletal Injuries and Overtraining 

Many runners fall into the trap of running almost every run at the same pace, landing somewhere in the moderately difficult intensity level.

This can lead to overtraining and overuse injuries because the same stresses and intensities are placed on the body stride after stride, run after run.

In contrast, when a runner constantly changes paces—running speedwork and slow runs—they introduce more stride variability and shift stresses on bones, muscles, and connective tissues. This can reduce the risk of injury and increase overall strength.

One a side note, if injury risk is something you are concerned about, be sure to include strength training in your routine.

#2: Cardiovascular Benefits

Cardiovascular adaptations are among the top benefits of Zone 2 training for runners. Because this type of training training takes place squarely in the aerobic zone, Zone 2 cardio strengthens the heart and lungs.

As the heart gets stronger, stroke volume increases, which means that the heart is able to pump more blood—and thus oxygen—out to the body every time it beats. This can effectively reduce heart rate because the heart becomes more efficient.

Capillary density increases, allowing for better perfusion of working muscles.

Additionally, training in Zone 2 stimulates an increase in blood plasma over time. This, in turn, also increases stroke volume, cardiac output, oxygen transport and delivery, and, ultimately, VO2 max.3Filipas, L., Bonato, M., Gallo, G., & Codella, R. (2021). Effects of 16 weeks of pyramidal and polarized training intensity distributions in well‐trained endurance runners. Scandinavian Journal of Medicine & Science in Sports32(3). https://doi.org/10.1111/sms.14101

A runner jumping.

#3: Improves Metabolic Health  

In addition to cardiovascular adaptations, Zone 2 training induces metabolic benefits. Running at the same pace every day limits improvement because the same physiological stresses are placed on the body with every run.

From a metabolic standpoint, the intensity level of a workout has a significant impact on the energy production pathways utilized.

Training too much at the same mid-range effort level, rather than capitalizing on the vastly different effort levels of polarized training, minimizes the potential training adaptations and metabolic improvements that can be gained by varying your paces and spending a lot of time running in Zone 2.

Running in Zone 2 increases the mitochondrial density in skeletal muscles, particularly in Type I muscle fibers.

Mitochondria are cellular organelles, or the powerhouse of the cell, that produce adenosine triphosphate, ATP, (energy) aerobically (in the presence of oxygen).

The greater the mitochondrial density of your muscles, the more energy your muscles can produce to fuel your activity, delaying fatigue. Zone 2 training can boost mitochondrial function.

Zone 2 training relies on aerobic metabolism (Krebs cycle and electron transport chain), whereas speed work and effort levels in zones 4 and 5 utilize anaerobic energy pathways (glycolysis and the phosphocreatine (PC) system).

Again, by spending time training in zone 2 as well as in higher intensity zones such as zones 4 and 5 with polarized training, the body is forced to rely on different pathways of energy generation. 

A person checking their heart rate.

This induces favorable adaptations in each pathway, making your body better equipped to handle the metabolic demands of running without your muscles producing painful byproducts such as lactic acid.

For this reason, polarized training involves metabolic flexibility, meaning your body can easily produce energy through any of the metabolic pathways and seamlessly flux between the reliance on different energy systems.

Finally, the metabolic adaptations of Zone 2 training allow the body to become more efficient at using fat rather than glycogen as a fuel source.

When your body gets better at meeting its energy needs by fat burning rather than using stored carbohydrates, you delay potential “bonking” or “hitting the wall.”

Seasoned marathoners may be aware of the dreaded onset of significant fatigue that may creep in around the 20-23 mile mark of a marathon; this is often when you’re body has used up any available glucose and depleted the body’s glycogen stores. 

Our bodies have a limited capacity to store carbohydrates in the form of glycogen, whereas even the leanest runners have enough body fat to fuel hours upon hours of exercise. 

Zone 2 training causes favorable adaptations in fat metabolism, allowing you to run faster while still burning fat for fuel rather than carbohydrates. Ultimately, this can be hugely beneficial for marathoners as well as those looking to burn body fat.

Two people running.

#4: Recovery Benefits

Because Zone 2 training is quite easy, it fully allows your body to recover from hard workouts. This reduces the risk of injury and allows you to be ready to attack the next speed workout with more energy and intensity. 

If you run a high-intensity interval training workout on the track on Monday and head out for a moderately intense zone 3 distance run on Tuesday, your body will carry over more accumulated fatigue to Wednesday than if you have taken your Tuesday recovery run as a true recovery workout in Zone 2.

As a result, your performance on Wednesday’s effort may suffer, and your risk of overtraining increases. In this way, training in Zone 2 helps your body bounce back and recover after hard workouts. 

How Much Time Should You Train In Zone 2 For Improvements In Endurance?

Most of your training should occur in your lower-intensity Zone 2 heart rate.

As a UESCA-certified running and triathlon coach, I recommend that at least 60-75% of your weekly running volume be Zone 2 cardio, the intensity level that forms your aerobic base.

To reap the benefits of Zone 2, long runs, recovery runs, and easy runs should all be run in Zone 2.

For more information on heart rate training, check out:

References

  • 1
    Kenneally, M., Casado, A., & Santos-Concejero, J. (2018). The Effect of Periodization and Training Intensity Distribution on Middle- and Long-Distance Running Performance: A Systematic Review. International Journal of Sports Physiology and Performance13(9), 1114–1121. https://doi.org/10.1123/ijspp.2017-0327
  • 2
    Lactate Testing & Training Zones – Rich Roll. (2009, July 10). https://www.richroll.com/blog/lactate-testing-training-zones/
  • 3
    Filipas, L., Bonato, M., Gallo, G., & Codella, R. (2021). Effects of 16 weeks of pyramidal and polarized training intensity distributions in well‐trained endurance runners. Scandinavian Journal of Medicine & Science in Sports32(3). https://doi.org/10.1111/sms.14101
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

1 thought on “Zone 2 Training: Build Your Aerobic Capacity + Improve Performance”

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.