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Low Heart Rate Training (Zone 2 Training)

Taren Gesell

Are you an athlete looking to improve your performance in endurance sports, particularly in running? The best but most underutilized way to improve is through low heart rate Zone 2 training.

Low heart rate training (also known as polarized training, aerobic training, Maffetone method training, low heart rate training, or 80/20 training) involves spending 70-80% of your total training hours at a very low heart rate. It has been proven as the absolute most effective way for athletes of all backgrounds to reach their goals.

However, training at a low heart rate is also one of the most difficult things for an endurance athlete to learn, which is why we’ve created this guide to help you. Whether you're a seasoned pro or just starting out, understanding heart rate training zones can help you take your training to the next level.


  • What is Zone 2 running
  • How to train in Zone 2
  • How to stay in Zone 2 while running
  • What the benefits are from Zone 2 running
  • How long it will take to see results
  • How to calculate your Zone 2 heart rate
  • How to avoid the most common mistakes runners make in their Zone 2 training sessions
Gretchen Clemens has used MOTTIV for the past couple of years to train for IRONMAN triathlons alongside her fiance Matt. They find training together a great way to strengthen their relationship bond!

Heart Rate Training Zones Explained

HR training zones are a way to measure the intensity of your workout and ensure you are training at the appropriate effort level to create the correct training effect while also balancing the training stress you put on your body.

There are five heart rate zones in the most commonly used system, which is the system we use and recommend for athletes using our training app.  Each training zone has a specific target heart rate range and a specific physiological goal, and we'll explain how much time training you'll want to do in each one.

Zone 1 Recovery/Warm-up: This is the lowest intensity zone and is typically used for warm-ups and really easy recovery workouts. Swimming tends to be in this zone. The target range for this zone is 50-60% of your maximum. Athletes should spend 20-40% of their total annual training hours in this zone.

Zone 2 Endurance: This zone is used for building endurance, creating mitochondria, and becoming metabolically fit so your body can burn fat as fuel. Athletes will spend a lot of time keeping their heart rate in Zone 2 during long runs and bike rides. The target HR range for this zone is 60-70% of your maximum. Athletes should spend 40-60% of their total annual training hours in this zone.

Zone 3 Tempo: This zone is used for building the ability to hold speed for a long period of time by increasing the ability to buffer lactic acid. Athletes will work on tempo pace up to once per week (and particularly when races approach, during bike rides and runs.) The target for this zone is 70-80% of your maximum. Athletes should spend 5-15% of their total annual training hours in this zone.

Zone 4 Lactate Threshold: This zone is used for improving your lactate threshold and increasing your V02 Max. Athletes can work in this zone with intervals of 10-60 minutes. The target HR range for this zone is 80-90% of your maximum heart rate. Athletes should spend 5-15% of their total annual training hours in this zone.

Zone 5 VO2 Max: This is the highest intensity zone and is used for improving your VO2 Max, increasing your top end speed, and teaching more muscle groups to fire. The optimal heart rate range for this zone is 90-100% of your maximum. Athletes should spend 5-10% of their total annual training hours in this zone.

While the five zone system can be calculated for your heart rate, running pace, or cycling power, we recommend using heart rate only for Zones 1 and 2 training; faster training should be done using pace, power, or perceived exertion.

4 Key Benefits of Zone 2 Training

Low heart rate running is a popular training method among all successful triathletes, runners, cyclists, and good coaches, but what exactly are the benefits you're getting from this type of training?

Benefit #1: Increased Mitochondria. Runners will often hear about athletes “having a big engine”. Mitochondria has a lot to do with the size of an athlete's engine because mitochondria are are the "powerhouses" of our body cells; they're responsible for producing adenosine triphosphate (ATP) which is the primary energy currency of the body.

More mitochondria = more ATP = more energy, which can help athletes perform for longer periods of time without fatigue. Additionally, increased mitochondria may also help with faster recovery from intense exercise; they are best increased with training in Zones 1 and 2.

Benefit #2: Better Use of Energy. A study published in the Journal of Strength and Conditioning Research in 2013 found that polarized training, where the majority of the athletes training was done at a low heart rate, resulted in greater improvements in running economy compared to threshold-style training where athletes spent much more time at higher intensities.  Polarized training athletes were able to run using much less energy than threshold athletes.

Benefit #3: Lower Stress on the Body. Zone 2 creates a lower stress response on the body. This study published in the International Journal of Sports Medicine in 2007 found that the nervous system is less disturbed by low heart rate running than intense running. This means that low-intensity training can be done more frequently and for longer periods of time without causing fatigue and burnout.

Benefit #4: Improved Race Performance. A meta-analysis published in the Journal of Sports Medicine in 2018 confirmed that race performances were better with a polarized training model than all other training styles, regardless of race type, training hours, or athlete experience. The polarized training method, where the majority of athletes trained in Zones 1 and 2, was by far the best training method when it came to running, cycling, and triathlon performance.

In conclusion, low heart rate running is a valuable training method for runners of all levels. It is effective for both elite athletes and recreational runners. It creates a lower stress response on the body and is an important factor in improving running performance. If you're looking to improve your running performance, low heart rate training is critical.

Matt Codiamat has been using MOTTIV to train for IRONMAN races with his fiance Gretchen Clemens (pictured above in this article). They love the flexibility of the training and the fact the training will always be tailored to their bodies individually.

The Science Behind Low Heart Rate Training

Zone 2 running has been shown to have immense benefits but what exactly is happening to your body when you're running in this heart rate zone?

Mitochondria Development

One of the key benefits of Zone 2 running is that it increases the number of mitochondria in your cells. As we’ve discussed, these are the powerhouses of the cell, responsible for producing energy through the process of cellular respiration.

When you're training in Zone 2, your body increases the density of mitochondria in your cells, which in turn allows your body to produce more energy during exercise.

Burning Fat as Fuel

Additionally, Zone 2 running helps train your body to burn fat as fuel. When you're working at a moderate intensity, your body is able to use fat as a primary source of energy, which helps improve your body's overall metabolic fitness. You will become more efficient at burning fat as fuel, which will give you more endurance to run for a longer period of time.

Lower Lactate and Cortisol Levels

Finally, Zone 2 running is effective in keeping lactate levels low and preventing the release of cortisol, a stress hormone that negatively impacts athletic performance when it’s kept too high for too long.

Lactate accumulates in the body during exercise above the top of your Zone 2 intensity. Cortisol can inhibit the body's ability to burn fat as fuel, increase inflammation, and disrupt sleep. Zone 2 keeps lactate levels low and prevents the release of cortisol.

When your training is balanced, and most of your time spent training is in Zones 1 and 2, your body is in a low state of stress.  This way, your body will be able to hit your fast training really fast and adapt to the fast training successfully. Also, when you’re in a low state of stress you’ll be less likely to get injured or sick.


Step 1: Calculate Your Heart Rate Zones

Calculating your heart rate zones using the correct method is an important step in optimizing your running performance and ensuring you are training at the right intensity.

There are a few different methods you can use to determine your HR zones, but we prefer to use the Karvonen Method as it tends to be the most accurate for the greatest number of people.  The Karvonen Method is also based on your unique heart rate physiology, as opposed to other methods which are based on arbitrary guesstimates of your heart rate.

We find that the Karvonen Method is almost as accurate for calculating these zones as lab testing, while other methods can give inaccurate zones 30-40% of the time.

The Karvonen Method Calculation

The first step in using the Karvonen calculator is to determine both your maximum and resting heart rate. To perform a maximum heart rate test, we recommend the workout below from our training app.

Once you have your maximum heart rate, you can then collect your resting rate by wearing a wrist-based heart rate monitor to bed for a few nights. If you don’t have a wrist based monitor, you can take your resting HR while lying down first thing in the morning, then use a number that’s 5-10 beats per minute lower than the reading you collected.

Finally, to determine your heart rate zones using the Karvonen Method, you will need to use the following formula: ((Maximum Heart Rate – Resting Heart Rate) x Intensity Percentage) + Resting Heart Rate. Or you can simply enter your maximum and resting rates into our calculator below:

HR Training Zones

It’s important to note that monitoring heart rate using a chest-based heart rate strap is the most accurate method; watch-based heart rate monitors can be inaccurate by as many as 40 beats per minute. Women can use an arm band if they cannot comfortably use a chest strap (for those who can use a chest strap, the strap should be placed just below the bra band).

Step 2: Incorporate Zone 2 Heart Rate Workouts into Your Training Plan

To begin incorporating these runs into your training schedule, here are the key points to remember:

  • Zone 2 training is typically done mainly in long runs and rides, recovery workouts, warm ups and cooldowns. Most swims are done in Zone 2 because the pressure of the water around your body will keep your heart rate lower.
  • Zone 1 and 2 training should comprise roughly 70-80% of your total training hours.
  • Low intensity training should be monitored by heart rate, not pace or power, so you may feel like you’re going very slow. Remember, this is okay!
  • As your fitness level improves, you don't need to update your HR zones very often. Instead, you should adjust your pace training zones regularly.

It can be very difficult to maintain a low heart rate in training, especially while running, on hills, or in heat. To make it easy on yourself, you should perform your low intensity training during the coolest part of the day on flat ground.

Common Mistakes in Zone 2 Training

Mistake #1: Thinking Zone 2 training has to be spent running. A big mistake that runners make when they get started with Zone 2 running is thinking all of their running workouts have to be spent running.

Instead, runners can turn their long runs into a hike mixing running with walking. This will naturally keep your heart rate low and reduce the risk of injury by hiking on trails instead of running on pavement.

Mistake #2: Training exclusively in Zone 2 to speed up the process. Another big mistake many runners make is that they think they can speed up the process by spending all of their time in Zone 2.

It's critical to have at least one fast run each week because low heart rate running increases your body's mitochondria, but fast running with a high heart rate teaches that mitochondria how to fire. Without that high intensity workout you’ll be building a lot of mitochondria that doesn’t truly know how to function, so you won’t be making much progress.

Mistake #3: Expecting improvements to happen quickly. Doing the bulk of your training at a low heart rate is the way to success in endurance sports, full stop! But it’s not a magic bullet that will create improvements instantly.

Total beginners may experience some quick improvements in the first several weeks, but generally it takes months to really start seeing the improvements build up.  However, the great thing about low heart rate training is that while improvements are slow, they can accumulate year after year. In other words, you can continue to get faster year after year using this type of training -- as opposed to other training methods where you’ll experience a plateau after just several months.

Mistake #4: Thinking they're making no progress if they have to walk to stay in an easy zone. At the start of this type of training, almost every athlete (even seasoned athletes with tons of experience) has to run/walk to stay under their zone 2 threshold. This is totally okay, even professional runners and triathletes will walk/run sometimes and struggle to keep their heart rate low. (This particularly happens in very hot weather or if the athlete is tired.) It can be humbling at first, but if you commit to never going at too high a training intensity, you'll soon find you no longer need to walk to stay under Z2 -- and that your zone 2 pace continues to get faster while your HR stays the same.

Example Zone 2 Workouts

Example of a slow, Zone 2 easy run in a triathlon training plan in the MOTTIV training app.
Example of a Zone 2 endurance ride in a Gran Fondo cycling race training plan in the MOTTIV app.
Example of a Zone 2 recovery run as part of a marathon training plan in the MOTTIV training app.

Monitoring Progress as You Train in Zone 2

One of the most effective ways to track your progress with your Zone 2 work is to track your heart rate vs pace or power. Improvements tend to happen consistently, but very slowly, so it may be hard for you to notice improvements.

By consistently performing rides and runs within the same 5-10 beats per minute in your Zone 2 workouts, and monitoring what pace or power you’re able to sustain, you can see how your body is adapting to your training and make adjustments as needed.

To monitor your progress, you should update your pace and power zones regularly. You don’t need to repeat the max heart rate test very often (if at all), once per year is plenty.

You should, however, update your running pace and cycling power zones every 2-4 months.  Below are the pace test and cycling FTP test that the athletes on our app use to keep their personal zones up to date.

Run Pace Time Trial test from the MOTTIV training app.
FTP Bike Test from the MOTTIV training app.


Performing 70-80% of your total training time at a low Zone 1 or 2 heart rate is truly the key to becoming the best athlete you can possibly be, unlocking your top athletic potential. We recognize that it may be hard to wrap your head around the fact that you’ll get faster by training slower, but studies and the thousands of athletes we’ve helped don’t lie.

If you want help getting a training plan with proper zones and the correct way to implement actually using those training zones, check out our training app here that will give you everything you need to do to reach your goals in running, triathlon, cycling, duathlon, or swimruns.

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Taren Gesell
Taren Gesell

"Triathlon Taren" Gesell is founder of MOTTIV and one of the world's top experts on helping adults become endurance athletes later in life. Best known for his YouTube channel and podcast, Taren is the author of the Triathlon Foundations series of books and has been published featured in endurance publications around the world.

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