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The most effective but most underutilized way to improve your endurance 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 endurance goals.

MOTTIV's training is based on the proven science of pyramidal training, so you can be sure that the training you're receiving as a user of the MOTTIV training app is exactly what you need!

But, training at a low heart rate is also one of the most difficult things for an endurance athlete to learn, so we’ve created this guide to help you.

WHAT YOU'LL LEARN IN THIS ARTICLE:

• What is Zone 2 running
• 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 avoid the most common mistakes runners make in their Zone 2 training sessions

Heart Rate Training Zones Explained

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

There are five heart rate zones in the most commonly used system.  Each training zone has a specific target heart rate range and a specific physiological goal.
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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. MOTTIV athletes will 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. MOTTIV athletes will 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 both bike rides and runs.) MOTTIV athletes will 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. MOTTIV athletes will 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. MOTTIV ahletes will 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 use heart rate only for Zones 1 and 2 training. Faster training will be done using pace, power, or perceived exertion.

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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. That's why you'll see both kinds of workouts in your MOTTIV training plan.

Mistake #3: Expecting improvements to happen quickly. Doing the bulk of your training at a low heart rate is the ultimate 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 you're making no progress if you 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.

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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.

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 amount 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 the way we write your training plans in the MOTTIV app, 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.

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Wrap-Up

We recognize that it may be hard to wrap your head around the fact that you’ll get faster by training slower, but scientific studies AND the thousands of athletes we’ve helped don’t lie!