Why Do Zone 2

Why do Zone 2?

When it comes to cardio training, understanding the nuances of different heart rate zones can significantly enhance the effectiveness of your workouts. One such crucial zone is Zone 2 cardio, which is a specific heart rate range known as the sweet spot for endurance training.

It is aerobic or base training which is a moderate-intensity workout where your heart rate is elevated to approximately 60-75% of your maximum heart rate.

A basic way to identify your Zone 2 heart rate, you first need to calculate your maximum heart rate (MHR), which is typically estimated using the formula:

Outside of testing your max heart rate, you can start with the number 220 and subtract your age, then multiply by 60-75% to find your ideal zone 2 starting point.

For example,  for a 39-year-old.  Take (220-39) X .60 for the low end and .75 for the high end.  So, my low end would be 108 BPM, and my high end would be 135 BPM using this starting point equation.

This is a basic equation to get a starting point based on a theoretical max heart rate.  I have tested my max heart rate, and I know it to be above the equation, which is 196 BPM, which now gives me a top end of 147 BPM.  If you have been following my journey here, you know most of my zone 2 work I am for 140-145 BMP average.    The gold standard would be combining this with blood lactate testing to identify your exact zone 2, where your body can continue to manage blood lactate without hitting saturation and tipping over into anaerobic cardiovascular work zones.  This would be top of zone 3 and beyond into the dark space of zone 5. 

But let us break down blood lactate more. 

Blood lactate, often referred to as simply “lactate,” plays a crucial role in endurance training and is closely tied to how your body produces and uses energy during prolonged periods of exercise. To understand blood lactate and its relationship with endurance training, let’s break it down:

Lactate, or lactic acid, is a substance produced by your muscles and other tissues when they metabolize glucose for energy. It’s a natural byproduct of glycolysis, a metabolic process that occurs when the body needs to generate energy quickly, such as during intense exercise.

Contrary to a common misconception, lactate is not a waste product or the cause of muscle fatigue. In fact, lactate can be a valuable energy source, especially during endurance activities.

A key concept in endurance training is the lactate threshold, also known as the anaerobic threshold. This is the exercise intensity at which lactate production in your muscles exceeds your body’s capacity to remove it from the bloodstream.  So, our goal of zone 2 training is to stay right under this threshold.

When you exercise at or above your lactate threshold, your body produces lactate faster than it can clear it away. This leads to increased blood lactate levels, which can cause muscle fatigue, discomfort, and reduced performance. Therefore, understanding and training at or near your lactate threshold is critical for endurance athletes and the amount of time in the anaerobic zone depends on your goals and your ability to recover from the training.  

Endurance training is about pushing your lactate threshold higher; simply, the higher your lactate threshold, the fitter you are.  That is why combining max heart rate with blood lactate testing for someone who is well-trained is the gold standard for maintaining proper zone 2 training.   Suppose the well-trained athlete were to just stick with their theoretical equation. In that case, there is a high probability they will see a reduction in their lactate threshold, reducing their overall fitness adaptation.  Although your max heart rate will improve through training, with aging, there is still a top end here, but even with aging, you can continue to improve your blood lactate threshold, which will move your zone 2 into the zone 3 area while still staying under your lactate threshold.  

One thing to caution here is there is still potential for over-training your heart.  There is a point in your zone work, in the 60-75% range, that your heart hits its maximum stroke volume of blood.  We want to work at the top end of our stroke volume but not push this into chronic overreaching for long periods of repetitive training.   More on this below, but let’s finish lactate.           

Through consistent endurance training, your muscles become more efficient at using oxygen and producing energy aerobically (with oxygen). This means they rely less on anaerobic processes that produce lactate.

Endurance training enhances your body’s ability to clear lactate from the bloodstream. This is achieved through improved mitochondrial health, blood circulation, increased capillarization (more tiny blood vessels near muscles), and better enzymatic activity for lactate removal.

A higher lactate threshold means you’ll experience less muscle fatigue and discomfort during endurance activities, allowing you to maintain a consistent pace more easily.

Training at or near your lactate threshold also improves your body’s ability to clear lactate after intense exercise, reducing post-workout soreness and speeding up recovery.  This is a critical point. Training near your threshold and still NOT going over it.  This is key to your ability to recover for the next training session.

Now we understand that blood lactate is a critical player in improving your endurance. Endurance training helps your body become more efficient at using oxygen, clear lactate more effectively, and raise your lactate threshold, leading to better endurance and performance. So, whether you’re training for general health and wellness, my main goal, or any endurance event, embracing the science of lactate can be the key to achieving your goals and going the distance. 

So, to review Zone 2 cardio primarily engages the aerobic energy system, gradually improving your body’s ability to utilize oxygen efficiently. This leads to enhanced aerobic capacity.

Contrary to a widespread belief that I have held onto for many years and had to debunk my own beliefs that zone 2 burns more fat, such as using it as its primary fuel source during that activity.  Dr. Andy Galpin goes into heavy detail on this.  New research shows that your body is going to use stored glucose first as its primary fuel source.   The body’s optimal fuel source for exercise.  It is not until 60-90 minutes into a training session that the body switches from using stored glucose to stored body fat.  At the end of the metabolic pathway, known as the Krebs Cycle, the body uses ATP (Adenosine triphosphate) regardless of the starting point of fat or glucose.  When your body has glucose readily available in the muscle and liver, this is the most efficient fuel source for energy expenditure, it is not until this fuel source is depleted that your body will start oxidizing fat into smaller carbon chains known as glucose, and then ATP.  Oxidation of fat takes longer for the body, so your body will use the easily accessible energy of glycogen first.  This is why training fasted or unfasted is a personal preference for most training sessions under 90 minutes as long as you are meeting your macro and calorie needs to support your active lifestyle on a daily and weekly basis.   Your total muscle mass also influences this.  More muscle means more stored glucose.  

For a later knowledge blog, I want to touch on the weight loss piece here, but in short, total caloric expenditure and consumption will decide if your body loses fat over time, such as weeks, months, and years.  But after you burn off all glucose, your body will fight to replenish your muscle and liver glycogen; depending on your caloric intake, your body will oxidize fat to replenish stored glycogen.    This is not suggesting starve yourself to lose fat and force this conversion.  There are many issues here, which will lead to other potential problems.   In a later blog, I will explain how to optimize fat loss.            

Back to Zone 2

The moderate intensity of Zone 2 cardio is gentle on your joints and muscles while still providing practical training. It allows for extended workout durations, which increase carbon utilization, which can lead to further caloric burn. Burning more carbon than the body has available can lead to less fat stored and more fat used over time. 

Another massive benefit is reducing the risk of injury associated with high-impact, high-intensity training.  Our bodies and health need high-intensity training, but only as much as our lifestyle allows us to recover physically.   Later I will break down how much and why high-intensity needs to be a part of our training program for both fitness and longevity goals.  You will never reach optimal with only zone 2 training.   I don’t train for the longevity game to be average; I train to be awesome and optimal.   But the bigger the zone 2 base, the better the high intensity will be, improving your V02 max and making you harder to kill.        

Zone 2 cardio facilitates quicker recovery after intense workouts. The improved aerobic capacity helps your body efficiently clear waste products and replenish energy stores, aiding in faster recuperation.  My increase in zone 2, is one of my main recovery tools, and you will find that your recovery from workout to workout will dramatically improve.   

Zone 2 for the longevity game comes down to a big point, which is managing blood sugar. 

For individuals managing blood sugar levels, exercise is a cornerstone of their wellness routine. Among the various forms of exercise, Zone 2 cardio training stands out as a potent tool in blood sugar management.

Regular exercise, especially in Zone 2, can significantly enhance insulin sensitivity. Insulin is a hormone that helps regulate blood sugar levels by facilitating glucose uptake into cells. When your cells are more sensitive to insulin, they can utilize glucose more effectively, thereby keeping blood sugar levels stable. This is also key to fat management.  

Zone 2 cardio encourages the body to use glucose as a source of energy during the workout. This can help in reducing elevated blood glucose levels, especially after meals, by facilitating the uptake and utilization of glucose by muscle cells.  Just to highlight.  More muscle equals more glucose utilization, even at rest, which helps manage blood sugar and also body composition, so NEVER be scared of adding more muscle if longevity matters to you. 

Stress can impact blood sugar levels by triggering the release of stress hormones like cortisol and adrenaline, which can lead to elevated blood glucose. Zone 2 cardio helps in managing stress levels, potentially aiding in better blood sugar control. Zone 2 is one of my most potent stress management tools.   Not only improving my resting heart rate, but also my HRV.  When I am consistent with my zone 2, my heart rate variability does tend to have a positive response. 

The best zone 2 method of training comes down to what you will do the most of and will be able to recover from.  Any sustained monostructural effort can provide great zone 2 training, such as running, rowing, cross-country skiing,  swimming, cycling, rucking, and hiking.  I personally found my Concept 2 bike erg to be the best for me, and second to that, rucking, and here is why. 

I love CrossFit and our Double Edge classes, one of the main reasons we built a gym.   Using low-impact tools such as the bike erg has the least amount of eccentric loading vs. running and is also not as high in full body fatigue like rowing can produce.  Rowing for 45-60 minutes can be very muscular fatiguing.  Cycling is something I enjoy, and I can recover from these sessions overnight very quickly.   The other training modalities I just do not recover from as well.  So cycling and rucking are my go-to for this kind of training.  Ultimately, you will do more of what you enjoy, and the goal for the longevity game is a minimum of 3 hours per week in zone two in a minimum of 20-minute sessions, but the optimal would be four 45-minute sessions per week, depending on your current base of fitness.  This is a minimum dose of 12 hours per month working in this zone as a goal for optimal longevity.

This amount of training works perfectly with my desire to CrossFit five times per week, which fills all the needs my body requires for strength development, muscle mass maintenance, anaerobic cardiovascular work, stability work, and all the other areas that are top priorities for my long-term health.   Our Double Edge classes hit 80% of everything you need for the longevity game.  But to optimize your longevity game, you need Zone 2, so I suggest finding something you enjoy outside the gym and start stacking time in this zone, building up to 3 hours per week.

I usually try for 30-45 minutes on Tuesday and Thursday in addition to my CrossFit training and another two sessions over the weekend to hit my 3 hour weekly goal.      

My purpose here is to explain how to use zone 2 for longevity, but I can also promise you that doing this will increase your sports performance dramatically.  But training for sports often needs specific training protocols to optimize your sport performance goals.   For example, if your goal is a 100-mile foot race, your zone 2 requirements will be dramatically different than mine for just optimizing my health for the long term.

Before you come at me about cardio-reducing muscle mass, I will explain how to optimize in a later knowledge post, but for most of us, don’t overthink this.  Lift heavy things and eat healthy.  Muscles will be forced to adapt.  But like everything, there are ways to optimize depending on your goals.   For me, although I know how to optimize for muscle gain around cardio training, I pay little to no attention to it in my current training plan.  I know my net gain in cardiovascular health and muscle mass maintenance will outperform over time.  Much of this comes down to how much time you have to train and which adaptations you want to optimize first.  I am happy to help any member at Double Edge lay out a plan to fill their voids and optimize their training time. Just reach out to me.          

Hope this helps and provides you with a valuable tool to optimize your longevity game.  As a disclaimer, this post was built based on my 15 years of real-life experience, the knowledge of Dr. Peter Attia, Dr. Andy Galpin, and some assistance using artificial intelligence to help my poor grammar as much as possible.  

Have a blessed day,

Coach Derek