Kathit Sondhi
Don’t you hate it when your coach asks you to slow down, to jog at a pace that makes you feel like you didn’t push hard enough? No burning lungs, no drenched shirt just an easy jog that left you wondering, was this even worth it?
When you exercise, the effort you put in can be categorized by five heart rate zones. These zones help you measure and plan your workouts by intensity, allowing you to target specific fitness goals. Zone 2 refers to an easy effort, where you can comfortably hold a conversation, falls typically in 60-70% of your maximum heart rate. Training in this heart rate zone, also commonly known as aerobic training, may feel too easy, but it plays a crucial role in building your aerobic base, improving running efficiency, and making you a stronger athlete over time.
So, why is training at this easy effort so effective? Let’s break it down
The Science Behind Zone 2 Training
Zone 2 training delivers incredible benefits for your entire body, enhancing your heart, lungs, muscles, and metabolism.
Stronger Heart Muscle
Zone 2 training promotes a healthy form of cardiac muscle hypertrophy by gradually enlarging the left ventricle and allowing it to pump more blood with each beat.
The moderate, steady effort in Zone 2 increases the amount of blood pumped by the heart with each beat (stroke volume). This results in your heart needing to beat less number of times per minute to provide the required blood supply to the body, both at rest and during submaximal exercise.
This is the primary physiological change that results in lower resting heart seen in elite athletes
Improved Capillary Density
Capillaries are tiny blood vessels that deliver oxygen and nutrients to muscles while removing waste products like carbon dioxide. Zone 2 training increases capillary density, helping muscles work more efficiently and recover faster.
Increased Mitochondrial Density
Mitochondria are the powerhouses of our cells, responsible for producing energy. They convert nutrients (like glucose and fats) into ATP (adenosine triphosphate), the energy currency our body uses to function.
Zone 2 training increases the size and the number of mitochondria in the muscles, improving the muscles' ability to produce energy aerobically.
This adaptation thereby improves fat oxidation, helping your body use stored fat as fuel instead of relying on carbohydrates and you become better at sustaining longer periods of aerobic activity without fatigue.
Blood Volume Expansion
Aerobic training increases plasma volume and red blood cell count, enhancing the blood's oxygen-carrying capacity, by release of a few hormones that promote fluid retention.
Better Blood Sugar Control
Zone 2 training has been shown to improve insulin sensitivity of the muscle, making it easier to utilize blood glucose.
It also increases few glucose transporter proteins and improves muscle glycogen storage
Reduced Blood Pressure
Aerobic training in Zone 2 helps reduce both resting and exercise blood pressure. This reduction is seen in both systolic and diastolic BP
Lower blood pressure means better blood flow and oxygen delivery to muscles, reducing fatigue allowing runners to maintain pace for longer and also decreases the risk of cardiovascular issues due to reduced strain on heart.
Increased Myoglobin Content
Myoglobin is a protein responsible for delivering oxygen to muscle cells. Aerobic training increases myoglobin content, thereby enhancing endurance capacity.
Ability to breathe efficiently during exercise
Aerobic training increases strength and endurance of our respiratory muscles, as well as improves oxygen extraction by the muscle cells.
Transforming Muscle Fibers for Endurance
Slow-twitch fibers (Type1) are necessary for everyday life and endurance. Zone 2 training primarily targets and increases the number and size of these muscle fibers by significantly improving the density of mitochondria within them, which enhances their ability to utilize oxygen and fuel during sustained exercise.
Additionally, Zone 2 training can encourage some fast-twitch (Type 2) fibers to adapt and behave more like slow-twitch fibers, making them more resistant to fatigue.
Improved Lactate Clearance
Zone 2 training improves our ability to utilize lactate as fuel for energy by the mitochondria
In short, Zone 2 training is a powerhouse for building endurance, improving efficiency, and boosting overall health. But let’s face it—staying in this zone for long periods can sometimes feel monotonous. The good news? It doesn’t have to be! With a few creative strategies, you can keep your workouts fresh, fun, and something to look forward to.
Let’s dive into some tips to make Zone 2 training anything but boring
Listen to something engaging (podcasts, rhythmic beats to match your Zone 2 cadence etc.)
Train with a friend. Having to keep a conversation going, will naturally help keep your training intensity/pace low and help you stay in the zone
Switch between running, stair climbing, or even brisk walking to keep things interesting
Use low impact training modalities such a elliptical, cycling, swimming, or rowing to maintain the heart rate zone
Use Zone 2 sessions as a time to practice mindfulness or deep breathing. Focus on your surroundings, your breath, or your form
Challenge yourself to go a little farther or longer each week in zone 2
The more consistent you are, the less monotonous it gets and the faster and more enjoyable it becomes! It’s all about building the foundation first.
Think about Eliud Kipchoge (world record holder and Olympic champion); he didn’t become a legend by going all out every day. A big part of his training happens in Zone 2—the kind of pace that feels comfortable but builds serious endurance. Kipchoge spends hours running at this steady pace, training his body to go farther and faster without burning out.
Stick with Zone 2, and you’re setting yourself up for greatness—just like the GOAT of marathons!
While these tips can make Zone 2 training more engaging, having the right tools can take your workouts to the next level. This is where Netrin Sports Technologies comes in. Designed to optimize your training experience, Netrin’s innovative solutions will help you stay in the right zone, track your progress, and make every session more effective.
The Netrin way of training
Our live trainer app provides personalized guidance to help you train more effectively by monitoring your performance in real time. It ensures that you stay within your target heart rate zones, which is key to optimizing your workout results. You can also check this post to understand how Netrin offers a streamlined and focused experience to support your fitness goals.
Taking Your Training to the Next Level
Zone 2 training may not be the most exciting part of your workout routine, but it’s one of the smartest investments you can make in your fitness journey. As your body adapts, training in this zone becomes more enjoyable, leading to a stronger heart, more efficient muscles, a boosted metabolism, and increased endurance. If your heart rate spikes even during a light jog, don’t rush, slow down, control your pace, and incorporate brisk walking if necessary.
Remember, real fitness isn’t about chasing quick highs; it’s about building a solid foundation for long-term success. Stick with it, and the rewards will follow.
Whether you're just starting your Zone 2 training journey or looking to optimize your current routine, we're here to help! Share your experiences, leave a question or comment below about how Zone 2 training has impacted your fitness and health. Connect with us today, your fitness goals are within reach!
References
Carter, J. B., Banister, E. W., & Blaber, A. P. (2003). Endurance training and heart rate variability. Medicine and Science in Sports and Exercise.
Convertino, V. A. (1991). Blood volume response to physical activity and inactivity. American Journal of Physiology - Regulatory, Integrative and Comparative Physiology.
Cornelissen, V. A., & Fagard, R. H. (2005). Effects of endurance training on blood pressure, blood pressure-regulating mechanisms, and cardiovascular risk factors.
Furlan, R., Piazza, S., Dell’Orto, S., Gentile, E., Cerutti, S., Pagani, M., & Malliani, A. (1993). Cardiac autonomic adaptations in elite athletes. Journal of the Autonomic Nervous System.
G. A. (2007). Cellular aspects of lactate metabolism during exercise. Medicine & Science in Sports & Exercise.
Hawley, J. A., & Lessard, S. J. (2008). Exercise training-induced improvements in insulin action. Acta Physiological.
Laursen, P. B., & Jenkins, D. G. (2002). The scientific basis for high-intensity interval training: Optimizing training programs and maximizing performance in highly trained endurance athletes. Sports Medicine.
Sawka, M. N., Convertino, V. A., Eichner, E. R., Schnieder, S. M., & Young, A. J. (2000). Blood volume and hemoglobin concentration in endurance-trained athletes. Medicine & Science in Sports & Exercise.
Haugen, T., Sandbakk, Ø., Seiler, S., & Tønnessen, E. (2022). The training characteristics of world-class distance runners: An integration of scientific literature and results-proven practice.
About the Author
Kathit Sondhi is a Gold Medalist in international combat sports and a coach at Netrin, specializing in heart rate-based training. With elite-level athletic experience and deep expertise in performance optimization, he is passionate about helping individuals train smarter, maximize results, and unlock their full potential through data-driven fitness strategies.
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