When I delved into the research on the minimum effective dose of strength training, I was blown away by the reward you can get with minimal effort.

Now, I am venturing into the world of the increasingly popular Zone 2 training. In the days before I had children and took on the role of a blogger, meeting a minimum cardio requirement for reaping the benefits was never a concern. My spare time was filled with countless hours of cycling and running throughout the week.

As time passed and my priorities shifted, both in terms of my family and my training goals, I found myself wondering two key things: Is cardiovascular training truly worth the investment of time? And if so, what is the absolute minimum I can do to attain those benefits?

Join me as we jump into the world of aerobic fitness and uncover the answers to these pressing questions.

What Is Zone 2 Training?

Zone 2 training, also known as “steady-state” or “base” training, is a type of aerobic exercise that is performed at a moderate intensity.

Exercise scientists have devised various training zones to assist athletes and coaches in understanding and leveraging the physiological responses and adaptations that take place in the body at varying exercise intensities. These zones are based on factors such as heart rate, lactate threshold, and oxygen consumption, and are used to target specific energy systems and muscle fibers in the body.

One common system divides training intensity into six zones. Zone 1 is the lowest intensity, which can include activities such as sitting down or walking around the house. This zone promotes recovery, improves blood flow, and aids in the removal of waste products from the muscles. As the intensity increases, the body begins to rely more on aerobic energy systems, which improve endurance and cardiovascular fitness. Zone 6 is the highest intensity, which can include activities such as all-out sprinting or deadlifting with heavy weights and low reps. This zone targets the anaerobic energy systems and muscle fibers, improving power output, speed, and strength.

Zone 1: The Recovery Zone - This zone is used for warm-up, cool-down, and active recovery. The primary energy source is fat.
Zone 2: The Endurance Zone - This zone is used for building aerobic endurance and burning fat. The primary energy source is fat.
Zone 3: The Tempo Zone - This zone is used for improving aerobic and anaerobic endurance and increasing lactate threshold. The primary energy source is carbohydrates.
Zone 4: The Threshold Zone - This zone is used for improving maximum aerobic capacity and increasing speed and power. The primary energy source is carbohydrates.
Zone 5: The VO2 Max Zone - This zone is used for building speed, power, and muscular endurance. The primary energy source is carbohydrates.
Zone 6: The Anaerobic Zone - This zone is used for building peak power and anaerobic capacity. The primary energy source is carbohydrates.

The Sport Science Of Zone 2

Zone 2 training recruits mainly type I muscle fibers. It primarily relies on the aerobic energy system by oxygen to create ATP (adenosine triphosphate), the molecule that provides energy to our muscles. This Zone 2 training mobilizes the highest amount of fat oxidation and stresses the mitochondria and oxidative capacity more than any other zone.

Zone 2 training is characterized by a heart rate range between 60-75% of an individual's maximum heart rate and typically involves endurance exercises such as rucking, running, cycling, or swimming (more below)

The Benefits Of Zone 2

Zone 2 training has a variety of health benefits, including:

Improved mitochondrial efficiency. Zone 2 training is particularly effective at improving mitochondrial efficiency, as it encourages the body to produce more of these energy-producing organelles. The more mitochondria there are in the body, the more ATP can be produced through fat oxidation. By exercising regularly in Zone 2, the body becomes more efficient at using oxygen to produce energy, which can lead to increased endurance and improved overall health. Additionally, improved mitochondrial efficiency may also help to prevent age-related decline in energy production and reduce the risk of chronic diseases.
Increased endurance: Engaging in Zone 2 training can help to improve endurance by increasing the body's ability to use oxygen for energy. This is because the muscles become better at using oxygen as a result of training in Zone 2, which can help to delay fatigue and improve overall performance.
In fact, most elite endurance athletes do what’s called 80/20 training where they do 80% of their workload in this Zone 2 training (including Kipchoge, the fastest marathoner ever). See Matt Fitzgerald’s 80/20 Running for a deeper dive into this, with training plans.
Improved fat metabolism: Zone 2 training is particularly effective at burning fat for fuel, which can help to improve overall body composition. As the body becomes more efficient at burning fat, it may also lead to improved insulin sensitivity, which can help to reduce the risk of developing metabolic diseases like type 2 diabetes.
Reduced risk of injury: Training in Zone 2 can help to improve overall body awareness and stability, which can reduce the risk of injury during physical activity. Additionally, regular training in Zone 2 can help to build a strong foundation of fitness that can help to prevent overuse injuries and other types of injuries related to physical activity.
Enhanced recovery: Zone 2 training can help to promote recovery and reduce the risk of overtraining. This is because Zone 2 training is less intense than higher intensity training, which can put less strain on the body. Engaging in regular Zone 2 training can help to promote active recovery, which can reduce the risk of soreness and stiffness, and improve overall recovery time.
Improved mental health: Zone 2 training can have a positive impact on mental health by reducing stress and anxiety. Exercise in general is known to stimulate the release of endorphins, which are natural mood boosters. Engaging in Zone 2 training can also provide a sense of accomplishment and contribute to a greater sense of well-being.

With these far-reaching benefits, it’s obvious that Zone 2 training is critical for health. After all, many of the aspects of the human body are directly a result of our bodi’s need to carry things and run for long distances so it’s no wonder that there our body smiles when we do this.

How To Know If You’re In Zone 2

There are two common methods to determine if you are in zone 2 training without using a heart rate monitor. These methods are called "the talk test" and the MAF method.

The talk test. The talk test involves monitoring your breathing and ability to carry on a conversation while exercising. During zone 2 training, you should be able to maintain a conversation with minimal breathlessness. If you are struggling to speak in full sentences or need to take frequent breaks to catch your breath, you may be working at too high of an intensity level and need to slow down.
MAF method. The MAF (maximum aerobic function) method involves calculating your maximum aerobic heart rate by subtracting your age from 180. This number represents the maximum heart rate at which you should be training to develop your aerobic system, that is your Zone 2 ceiling. During zone 2 training using the MAF method, you should aim to keep your heart rate within 10 beats below your maximum aerobic heart rate.
For example, if you are 40 years old, your maximum aerobic heart rate would be 180 - 40 = 140 beats per minute. To train in zone 2 using the MAF method, you would aim to keep your heart rate between 130-140 beats per minute.
Measure your lactate. Measuring your lactate is the most accurate way to determine if you’re in Zone 2. To do this you would measure your lactate using a drop of blood from a glucometer. A reading between 1.7 and 1.9mmol means that you’re in Zone 2.

Of course, always consult with a healthcare professional before starting any new exercise program.

Ways To Do Zone 2 Training

When you do Zone 2 training you need to stay in Zone 2 training without oscillating in effort or speed. This type of training is the duration of the time spent in it and not the average. You will naturally start in Zone 1 but once you are in Zone 2, the goal is to stay there for the long haul.

Here are ways to do Zone 2 exercise.

Running: Running may be the easiest way to do Zone 2 training. Most runners tend to run in the gray zone: Zone 3. So whether you’re experienced or not, this Z2 pace will likely feel really slow but if you put in enough time with it you’ll see the speed increase while the hear rate states the same.
Rucking: Rucking involves walking or hiking while carrying a weighted backpack. A little weight goes a long way. The rule of thumb with the weight of rucking is to start with a weight that is challenging but manageable, and then gradually increase the weight as you get stronger. A good starting point is to ruck with a weight that is equal to 10-15% of your body weight.
For parents, you can also use your kids. For kids who are small enough, wear them on your chest with a baby carrier or you can wear larger kids on your back with a backpack like the Deuter child carrier pack. I use both of these while bringing an empty stroller with me. Once they get tired then I transition them to the stroller and start a slower Z2 run.
Cycling: Cycling is another great way to get your heart rate up and improve your cardiovascular health. Compared to running or rucking, you may have to exert more effort to get that heart rate in Zone 2 since there is less impact and thus, less exertion.
Swimming: Swimming is another low-impact exercise that’s great for Zone 2 training.
Treadmill or Elliptical: For most people, walking tends to be a Zone 1 activity, however, walking with a brisk pace, up hills, or with some added weight (i.e. rucking) can get you into that next zone. Peter Attia uses a 15% incline on a treadmill at about 3-3.4 miles per hour. You can modify the angle or the speed/resistance on the treadmill or elliptical to hit your range.
Rowing: Whether it’s on the erg or on the water, rowing is a great full-body workout to use as a way to hit that Zone 2 steady state.

If you’re using a watch that tracks your heart rate, see if you can set a max heart rate number so that it indicates when you’re over that number.

It’s also worth noting that your zone will vary depending on your fatigue. If you’re under-rested, overworked, or in an otherwise stressed state, your nervous system will feel it and it will be reflected in your training and recovery. A good way to determine how ready your body is for training is to use heart rate variability (HRV). Check out the below articles for a deeper dive into this.

The Minimum Effective Dose

The minimum effective dose (MED) refers to the smallest amount of a substance or intervention that produces a desired outcome or effect. This concept is often used in medical and scientific research to determine the optimal amount of a drug or treatment that is needed to produce a therapeutic effect. The idea is to use the lowest possible dose that will still provide a meaningful benefit, in order to minimize the risk of side effects and reduce costs.

The MED can be used in various contexts: caloric intake, lifting, productivity, meditation, sleep, supplements, medications, sun exposure, etc. This article will focus on the minimum effective dose of exercise, specifically Zone 2 training. The question, then, comes down to: what is the least amount of time spent in zone 2 to achieve the health benefits?

What Is The Minimum Effective Dose For Zone 2 Training?

Determining a minimum threshold for Zone 2 training is difficult because there is not adequate evidence-based research that looks specifically at this. Fortunately, there are very intelligent people who are fascinated by this topic who have looked at it.

Peter Attia, host of The Drive podcast, author of Outlive, and a physician focused on longevity; considers Zone 2 training to be an essential part of health and one of his four pillars of fitness (stability, strength, and high intensity/anaerobic capacity being the others).

Attia interviewed one of the leading experts in this field, Iñigo San-Millán, in an interview on his podcast where they dove into the nitty gritty of Zone 2 training. For background, Iñigo San-Millán, Ph.D is a renowned physiologist who specializes in exercise-related metabolism and he is the head coach of the World Tour cycling team UAE Team Emirates and the personal coach of Tour de France winner Tadej Pogačar.

Through this interview (and some other discussions on the topic), the minimum effective dose of Zone 2 training emerges. Attia says,

“…it’s looking like the minimum effective dose is probably about 3 hours a week, ideally delivered at about 45-60 minute intervals.”

So how much Zone 2 cardio per week? If you’re just getting started, he suggests 2 hours a week but spread out over multiple days. Training once per week will lead to a loss of fitness over time. Training twice per week may help to maintain fitness, but three or more days per week are necessary to see improvements.

What I Do

Zone 2 training is the kink in my fitness chain right now. Before kids (and when I started doing more of an 80/20 approach to endurance training) I would be able to hit this minimum effective dose consistently with running or cycling. Forty-five minutes, 4 days a week? No problem.

Since having kids (and starting a blog), Zone 2 training has taken a backseat. I prioritize strength training and HIIT which have higher intensity levels but lower time commitments. In the spring, summer, and fall I take the first kid to wake up on a longer walk/ruck/run with me on the weekends (see above for this strategy) but this is usually twice a week at best.

Recently, however, I’ve been playing with a workaround for the sacrificial lamb that is Zone 2: cycling while writing. My family recently bought me a Flexispot Bike Desk for my birthday which allows me to get my writing in while keeping my heart rate in Zone 2.

It’s still fresh so I’m learning what I can do (write, research) and can’t do (interviews, hang out with my wife) while determining how much this low-end aerobic training impacts my sleep. I’m not sure if this will allow me to hit the Z2 MED but I plan to continue to experiment with it to see if it improves my aerobic capacity, sleep, and fitness more generally.

Takeaway

Zone 2 training is a type of aerobic exercise that is performed at a moderate intensity. It is beneficial for improving endurance, burning fat, enhancing recovery, reducing the risk of injury, and stimulating mitochondria and oxidative capacity.

A few approaches to determine your Zone 2 are to use the talk test, the MAF method, or lactate testing. There are a variety of ways to do this type of training including slower running, faster walking or rucking, cycling, or swimming. It’s important, however, to maintain your heart rate in this second Zone for the duration of the exercise.

The minimum effective dose (MED) of Zone 2 training is 3 hours a week for 45-60 minute intervals.

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The Minimum Effective Dose of Zone 2 Training