Exercise for health - Part I

Zone 2 training - ultimate evidence-based tool for improving and maintaining long-term health. The Definitive Guide.

What is the single, most important tool for improving and sustaining your health, slowing cellular ageing, improving metabolic health and aerobic capacity?

Short answer: Zone 2 training.

Handling the physical demands of daily life as we age requires some effort (unfortunately). Being able to put your hand luggage into an overhead compartment might be easy for a 20-year-old young male, but quite demanding for 70-year-old female traveler.

In order to remain fit and healthy throughout life, a well-rounded training program is required. It includes four core elements: stability, strength, aerobic efficiency, and peak aerobic output:

• Aerobic Efficiency - to sustain energy levels, perform daily tasks, improve fat metabolism, lower risk of hear disease and improve cardiovascular health, enhance recovery, endurance, maintain cognitive function, and ensure long-term mobility, personal independence and overall quality of life.

• Stability to prevent falls and minimise risk of injuries (main reason of disability)

• Strength to be able to perform basic daily tasks, prevent muscle mass loss, prevent injury and maintain mobility

• Peak aerobic output - to be able to survive a heart attack, live longer and recover from injury

These pillars may not all be equally important for athletes who specialise in certain single or narrow type of activity. But if you are not an elite athlete, or if your primary "sport" is enjoying a healthy life (and you want to continue being good at life as you age), it’s essential to work on mastering each of these areas.

To put it simply, whatever your health is at the moment, it will not last forever. If you care about remaining independent and would like to be able to enjoy your life as you age, you should start working out now.

Zone 2 training is one of the critical pillars of health and longevity, and is required for improving your aerobic efficiency, as well as your peak aerobic output (indirectly).

WTF is Zone 2?

If you have accidentally tried to google what “Zone 2” is, you should now be confused. A short online search gives multiple conflicting information. While the internet gurus argue about thresholds and definitions, we are going to stick to science!

Zone 2 is the highest level of effort that an individual can achieve without accumulation of lactate¹.

You will immediately notice that the definition above does not solely rely on a generic range of heart rate. This is because Zone 2 is based on what is metabolically happening in each cell of your body (it is a function of how each cell obtains its energy).

It is also the reason why Zone 2 exercise impacts every cell in your body, and why this type of training is critical for cellular and mitochondrial health (and ultimately your well-being and longevity)

WTF is Lactate, and why does it accumulate?

Brace yourself for a short class in biochemistry and physiology.

Every cell in your body, including your brain and muscles, requires usable energy to perform its function. The energy is obtained by breaking down carbohydrates and fats. The “unit” of this energy in your body is in the form of ATP. The most efficient way for cells to produce ATP (energy) is through a process called oxidative phosphorylation, where molecules derived from fats are oxidised (meaning: oxygen is required) in the mitochondria.

This process, also known as aerobic respiration, is the primary energy source for Type I ("slow-twitch") muscle fibres. These fibers have a higher density of mitochondria compared to the "fast-twitch" Type IIa and Type IIx fibers. During low-intensity activities, when energy demands are relatively low, fats become the main fuel, and it's primarily the Type I fibres that are engaged in generating movement.

As exercise intensity ramps up, the body can't rely solely on the mitochondria for ATP production and turns to faster, less efficient processes outside of the mitochondria. This additional process which generate a substance called lactate as a byproduct.

Carbohydrates can be used for production of energy (ATP) through aerobic and anaerobic pathways. However, fat oxidation can happen only in the mitochondria². Therefore as the demand for energy increases, your body shifts towards using more carbohydrates as the primary fuel. Therefore, as the demand for energy continues to rise, the reliance on these non-mitochondrial pathways increases (and the “byproduct” of this process - lactate (lactic acid) - starts to build up in your body.

While lactate can be metabolised by the mitochondria, higher production rates eventually outpace the mitochondria’s ability to clear it, leading to a buildup of lactate.

When lactate levels reach around 2 mM, it begins to “spill over” into the bloodstream, causing a sharp increase in blood lactate. The level of exercise intensity at which the lactate will “spill over” to blood stream and start accumulating in your body is your individual Zone 2 Threshold³.

Example of a metabolic test used to indirectly measure mitochondrial capacity during exercise through measuring FATox and blood lactate levels. Modified from San–Millán and Brooks, 2018 (reference 3)

What you should now be able to understand that YOUR individual Zone 2 threshold is unique to you. It also changes throughout your life and can be improved (moved to the right on the graph) with appropriately targeted exercise. This threshold varies depending on your personal cellular health, as it reflects how effectively your mitochondria can clear lactate as it's produced.

For top-tier endurance athletes, this threshold might be around 4 W/kg (Watts per kg of body weight), while for those with severe metabolic issues, it could be under 1 W/kg. Additionally, this threshold roughly aligns with the point where fat oxidation is at its peak.

Therefore, a high Zone 2 threshold indicates a strong capacity for fat oxidation, which is a good marker of mitochondrial health.

Why does it matter?

Simply out - training at your lactate threshold level will increase it⁴. Which means that you will be able to improve your body’s ability to oxidise fat, and improve “health” of each cell in your body.

Why is it good for you? Because mitochondrial health, or its decline, is a key factor in aging⁵ and in the development of a huge range of diseases (including cardiovascular disease⁶, neurodegenerative conditions⁷, and metabolic syndrome⁸. Enhancing mitochondrial function through practices like Zone 2 training has been shown to improve insulin sensitivity and could even help reverse pre-diabetes⁹.

The benefits of improving your lactate threshold go beyond disease prevention. They play a crucial role in improving physical function by building a strong aerobic foundation. Zone 2 training indicates how well your cells can oxidise fat for fuel, forming what’s known as your individual “aerobic base.” This base is essential for the body’s ability to maintain low-intensity efforts over long periods, which is key to overall endurance and stamina.

Zone 2 training is also essential for maximising your peak aerobic capacity, which will be covered in a separate article (it comes with its own set of spectacular health and well-being benefits).

If this is all individual, how can I ever tell if I am in Zone 2?

By using a blood lactate meter (taking a blood sample from your finger). In fact, this is how most professional performance athletes monitor their results over time.

The devices can be bought online, and are similar to the ones that people with diabetes use to measure their blood sugar levels (in fact, some devices can measure both; they simply require different strips).

The challenge is that those devices can be expensive, costs accumulate over time, and the testing is not pleasant. Furthermore, for someone who is in a really poor shape, relying on blood lactate measurements offers little practical insight, because couch potatoes will have elevated lactate levels even at rest, and will experience a significant spike as soon as they start even light exercise.

In other words, lactate levels aren't a reliable measure of exercise intensity until a certain baseline level of fitness has been established.

Therefore, in practical terms, you will need to use some brainpower to assess if you are in Zone 2 based on two parameters: HR (Heart Rate) combined with RPE (Rate of Perceived Exertion).

Heart Rate

Most people don’t know what their maximum heart rate (max HR) is. If you are in the small minority who know their maxHR, just read the next paragraph, and skip the rest. If you are like most people - you will need to skip the next paragraph and focus on what comes next.

If you already know your max HR because you have done a VO2max test or cardiopulmonary exercise test (CPET), you can estimate your Zone 2 range as a percentage of that maximum HR. For those who are in poor shape, starting at 70-75% of max HR is usually appropriate. In contrast, more trained individuals can aim for a slightly higher range, closer to 78-80% (but not exceeding 80%) of max HR.

If you are a normal person, and have no idea what your maxHR is, you will need a calculator to estimate your Zone 2. The most reliable way is by using the so called 180 Formula.

It is quite simple: subtract your age from 180¹⁰.

For example, a 40-year-young guy like me, you would start with a target Zone 2 heart rate of 180 – 40 = 140 bpm. From there, adjustments will need to be made: subtracting 5-10 beats per minute (bpm) if your primary activity is clicking the button on the TV remote (or when recovering from illness or injury, or dealing with conditions like asthma or obesity). If (unlike me) you are a highly trained athlete who exercises for more than 2 hours daily, and you have no significant health concerns, you might add 5-10 bpm to the baseline.

This approach suggests that a 44-year-old could have a Zone 2 range somewhere between 126 and 146 bpm.

Now, you will need to cross-check this estimate with perceived exertion (RPE) to ensure accuracy, regardless of the method used. Otherwise, you will not benefit optimally from your training.

Rate of Perceived Exertion (RPE)

RPE is essentially your subjective sense of how hard your body feels it's working during exercise. A practical way to use RPE for determining Zone 2 is through your ability to speak:

• If you can comfortably hold a conversation while working out, you're likely to be below Zone 2.

• If you find it impossible to speak, you're above Zone 2.

Zone 2 can be therefore thought of as the level where speaking is uncomfortable but still doable. For example, if you would need to answer the phone while working out in Zone 2 the person on the other end will know that you are working out; you would be able to manage the conversation—it just won’t be enjoyable.

CAUTION
DO NOT use fitness trackers to monitor if you are in your Zone 2!

Most fitness devices will define five zones based on percentages of maxHR, yet for unknown reasons they will assign Zone 2 to somewhere around 60-70% of your maxHR, which is too low for most people, as it will not trigger the required mitochondrial lactate processing thresholds, and therefore will NOT improve your mitochondrial capacity over time!

Other power meters (and gym exercise machines) will define seven exercise zones. Those are even worse, because the Zone 2 range can be as low as 55% of your functional threshold power, and will drastically underestimate the power required to achieve your lactate thresholds.

In other words - most of the gym equipment and “fitness” devices will not help you to achieve your health goals. Ignore the readings from those devices, and stick to the method I have described above.

You will also save some money.

How to train? How often? For how long?

When planning how to incorporate Zone 2 training into your exercise routine (which you should do), one of the key questions to consider is how much Zone 2 training is necessary to raise your Zone 2 threshold, thereby improving mitochondrial health and your capacity for fat oxidation. Unfortunately, there isn’t a one-size-fits-all answer, as the amount needed largely depends on your current fitness level. We will also discuss the impact of food and medications on your efforts.

Frequency