If you have at all been dialed into the latest research on healthspan and longevity, it will come as no surprise to you that there's one activity that stands head and shoulders above the rest for improving health markers and ensuring a long, healthy life: resistance training. But if lifting weights is the king, then Zone 2 cardio is a close second and is making up ground quickly. The more we learn about the immense benefits of having a robust, efficient cardiovascular system, the more important it becomes to not skip those cardio sessions. If you want to stack the odds of living a long, healthy, independent, capable life in your favor, then getting your cardiovascular work in is non-negotiable.

What is Zone 2 Cardio?

Zone 2 cardio is a form of aerobic exercise performed at a specific intensity level, where your heart rate is about 60-70% of your maximum. The easiest way to estimate your Zone 2 heart rate is with the Maffetone Formula: 180 minus your age. Depending on your fitness level, this may not be exact. For instance, if you’re 35, your estimated Zone 2 heart rate would be 145 beats per minute (bpm). This range ensures that you’re working hard enough to benefit your cardiovascular system but not so hard that you’re out of breath. It’s a steady-state effort where you can still hold a conversation (although slightly uncomfortably), also known as the “fat-burning zone” because at this intensity, your body uses fat as a primary fuel source.

Is Heart Rate a Good Way to Measure Zone 2?

Using heart rate to measure Zone 2 is a practical and accessible method, but it's not without its limitations. Heart rate can be influenced by various factors, including hydration levels, caffeine intake, and stress. To get the most accurate measure of your Zone 2 intensity, it’s essential to use a heart rate monitor but also consider these additional tips:

Consistent Monitoring: Regularly track your heart rate during different activities to understand how your body responds.

Perceived Exertion: Combine heart rate monitoring with perceived exertion (how hard you feel you’re working). In Zone 2, you should be able to maintain a conversation if you had to.

Talk Test: You should be able to complete a sentence with some effort.

Why Zone 2 Should Make Up 80% of Your Cardio Training

The answer isn’t always working as hard as you possibly can. Although, admittedly, the simplicity of this approach is appealing. In many ways, it would be great if all you had to do to maximize health and lifespan was to hit the gas pedal to the floor as often as possible. Alas, this is not, for better or worse, the answer to ideal health. That puzzle requires a bit more thought and discipline.

This is where Zone 2 cardio enters the chat. Zone 2 should constitute the majority of your cardiovascular training because it provides a solid aerobic base essential for overall endurance and health. When 80% of your cardio workouts are in Zone 2, it allows your body to develop the efficiency needed for longer, more intense sessions without overtraining. This approach, often referred to as the 80/20 rule in endurance sports, balances the high-intensity workouts (20%) with lower-intensity efforts (80%), ensuring sustainable progress and reducing the risk of injury. In contrast, relying solely on High-Intensity Interval Training (HIIT) can lead to burnout, increased risk of injury, and inadequate recovery. HIIT is great for improving anaerobic capacity and burning calories quickly, but without the foundation provided by Zone 2 cardio, you will likely find yourself constantly fatigued, overtrained, and more susceptible to injuries and illnesses.

High-Level Overview of Some of the Benefits of Zone 2:

Improved Aerobic Capacity: Zone 2 cardio enhances your body's ability to utilize oxygen efficiently, which is essential for endurance and cardiovascular health. When you train in Zone 2, your heart pumps more blood per beat (stroke volume), leading to a stronger and more efficient heart.

Enhanced Fat Metabolism: Exercising in Zone 2 maximizes fat oxidation, making your body more efficient at burning fat for energy. This is beneficial for weight management and metabolic health. A study published in the American Journal of Physiology found that moderate-intensity exercise increases the ability to oxidize fats compared to higher intensities.

Mitochondrial Health: Research in Cell Metabolism highlights that aerobic exercise, especially at moderate intensities like Zone 2, increases mitochondrial biogenesis and function. Mitochondria are the powerhouses of cells (where are my high school biology teachers at!?), and improving their function is crucial for energy production and reducing oxidative stress, which is linked to aging and various diseases. I’ll dive deeper into this later.

Improved Insulin Sensitivity: Regular Zone 2 cardio helps maintain insulin sensitivity and glucose metabolism, reducing the risk of metabolic diseases. The Diabetes Care journal published a study showing that moderate-intensity exercise significantly improves insulin sensitivity, which is critical for preventing and potentially reversing type 2 diabetes.

Cardiovascular Health: Studies in the Journal of the American College of Cardiology show that moderate-intensity exercise like Zone 2 cardio is linked to a lower risk of cardiovascular events and mortality. This is because it helps reduce blood pressure, improve cholesterol profiles, and enhance overall heart function.

Reduction in Chronic Inflammation: Chronic inflammation is a risk factor for many diseases, including heart disease, diabetes, and cancer. Zone 2 cardio has been shown to reduce markers of inflammation in the body like C-Reactive Protein (CRP), promoting overall health and longevity.

Mitochondrial Health: A Deeper Dive

Your 8th grade biology teacher referred to mitochondria as the powerhouses of the cell for a good reason. These tiny organelles are responsible for producing the energy that cells need to function. They convert nutrients into adenosine triphosphate (ATP), the energy currency of the cell, through a process called oxidative phosphorylation. We could nerd out for days on this whole process but at the end of the day, I want you to remember that the mitochondria takes the calories we eat and converts it into the engery we need to survive. The efficiency and health of your mitochondria are crucial for overall energy levels, cellular health, and longevity. Personally, this understanding is what motivates me to get off my ass and get to work. With more healthy and efficient mitochondria, your body becomes more effective at virtually everything.

How Zone 2 Cardio Benefits Mitochondrial Health

Increases Mitochondrial Biogenesis: Mitochondrial biogenesis is the process by which new mitochondria are formed within the cell. Think, more mitochondria, more energy production, improvement in just about every system in the body. Zone 2 cardio has been shown to stimulate this process, leading to an increase in both the number and efficiency of mitochondria. This means your cells become better at producing energy, which is vital for sustaining physical activity and supporting literally almost everything we would do as human beings.

Improves Mitochondrial Function: Not only does Zone 2 cardio increase the number of mitochondria, but it also improves their function. Better-functioning mitochondria mean that your body can produce more ATP with less effort, reducing fatigue and enhancing endurance. This improvement in mitochondrial efficiency also helps reduce the production of reactive oxygen species (ROS), which are harmful byproducts of cellular metabolism that can cause oxidative stress and damage cells.

Enhances Fat Oxidation: Zone 2 cardio trains your mitochondria to utilize fat more efficiently as a fuel source. During prolonged, moderate-intensity exercise, your body relies more on fat oxidation, sparing glycogen stores (energy stored in muslces) and improving metabolic flexibility. This adaptation is beneficial not only for endurance performance but also for weight management and metabolic health.

Reduces Oxidative Stress: Improved mitochondrial function leads to a reduction in oxidative stress. Oxidative stress occurs when there is an imbalance between the production of ROS and the body’s ability to detoxify them. Chronic oxidative stress is linked to aging and various diseases, including cardiovascular disease, neurodegenerative disorders, and cancer. By enhancing mitochondrial efficiency, Zone 2 cardio helps mitigate oxidative stress, promoting cellular health and longevity.

Supports Cellular Repair and Maintenance: This can get really “sciencey” so bare with me. It’s important! Regular Zone 2 cardio activates pathways involved in cellular repair and maintenance, such as the AMP-activated protein kinase (AMPK) pathway. AMPK is an enzyme that plays a critical role in cellular energy homeostasis. It is activated in response to low energy levels and stimulates processes that restore energy balance, including enhancing mitochondrial function and promoting autophagy (the removal of damaged cellular components).

Delays Age-Related Decline: As we age, mitochondrial function naturally declines, leading to a decrease in cellular energy production and an increase in oxidative damage. Regular Zone 2 cardio helps to counteract this decline by maintaining mitochondrial health and function. This can delay age-related decreases in muscle mass, strength, and endurance, contributing to a higher quality of life and extended healthspan.

Practical Tips for Maximizing Mitochondrial Benefits from Zone 2 Cardio

Consistency is Key: Regular, consistent Zone 2 cardio sessions of AT LEAST 30 minutes are more effective than sporadic high-intensity workouts for improving mitochondrial health.

Monitor Your Intensity: Use a heart rate monitor to ensure you are staying within the Zone 2 range. Over time, as your fitness improves, you may need to adjust your heart rate targets.

Combine with Strength Training: While Zone 2 cardio is excellent for mitochondrial health, combining it with resistance training will make you a machine.

Although High-Intensity Interval Training (HIIT) may seem sexy due to its time efficiency and immediate intensity, it could be eating away at your resistance training gains, leading to overuse injuries, and/or preventing you from properly recovering. That’s not to say HIIT doesn’t have its place. Incorporating HIIT into your training is beneficial, but it should only constitute about 20% of your cardiovascular work. The foundation, however, should be built on Zone 2 cardio.

Zone 2 training allows you to build a solid aerobic base, enhance mitochondrial health, and improve overall metabolic function without the risk of overtraining. In fact, most people find that it improves their ability to recover. By balancing your cardio regimen with 80% Zone 2 and 20% HIIT, you can maximize the benefits of both approaches, ensuring sustainable progress and promoting long-term health and longevity.

Incorporating Zone 2 cardio into your fitness regimen can have profound effects on your mitochondrial health, leading to increased energy, improved metabolic function, and enhanced longevity. By understanding and leveraging these benefits, you can optimize your training for a long, healthy, and active life.

Until Next Time,

Jake Louro

Louro Training

References:

Karn, J. P. L., & Kumar, N. (2022). Effect of Cardio Exercise, Resistance Training, or Combined Exercising on Cardiovascular Disease Risk Factors in Type 2 Diabetes Patients. Fortune Journal of Health Sciences. Click here to read.

Boulé, N., Kenny, G., Haddad, E., Wells, G., & Sigal, R. (2003). Meta-analysis of the effect of structured exercise training on cardiorespiratory fitness in Type 2 diabetes mellitus. Diabetologia, 46, 1071-1081. Click here to read.

Shepherd, S., Wilson, O., Taylor, A. S., Thøgersen‐Ntoumani, C., Adlan, A., Wagenmakers, A., & Shaw, C. S. (2015). Low-Volume High-Intensity Interval Training in a Gym Setting Improves Cardio-Metabolic and Psychological Health. PLoS ONE, 10. Click here to read.

Madden, K. (2013). Evidence for the benefit of exercise therapy in patients with type 2 diabetes. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy, 6, 233-239. Click here to read.

Grelier, S., Serresse, O., Boudreau‐Larivière, C., & Zory, R. (2013). Effects of a three-month combined training program on the cardiopulmonary and muscle strength capacities of type 2 diabetic subjects. The Journal of Sports Medicine and Physical Fitness, 53(1), 56-64. Click here to read.

Veeranki, S., Givvimani, S., Kundu, S., Metreveli, N., Pushpakumar, S., & Tyagi, S. (2016). Moderate intensity exercise prevents diabetic cardiomyopathy associated contractile dysfunction through restoration of mitochondrial function and connexin 43 levels in db/db mice. Journal of Molecular and Cellular Cardiology, 92, 163-173. Click here to read.

Phillips, B., Kelly, B. M., Lilja, M., Ponce-González, J., Brogan, R. J., Morris, D., Gustafsson, T., Kraus, W., Atherton, P., Vollaard, N., Rooyackers, O., & Timmons, J. (2017). A Practical and Time-Efficient High-Intensity Interval Training Program Modifies Cardio-Metabolic Risk Factors in Adults with Risk Factors for Type II Diabetes. Frontiers in Endocrinology, 8. Click here to read.

Colberg, S., Albright, A., Blissmer, B., Braun, B., Chasan-Taber, L., Fernhall, B., Regensteiner, J., Rubin, R., & Sigal, R. (2010). Exercise and Type 2 Diabetes. Medicine and Science in Sports and Exercise, 42(12), 2282-303. Click here to read.