Lever #3: Exercise — Part One: Aerobic & Anaerobic
Understanding aerobic and anaerobic exercise, the potency of exercise as a drug, and how to deploy the principle of minimum effective dose.
“If you knew somebody who had low cardiorespiratory fitness and didn’t want to take the steps that were necessary to get into even average or above average fitness, you would be able to say to them, ‘Do you realize the choice you’re making is more illogical than a smoker who continues to smoke?’… And it’s no comparison. It’s no comparison in terms of the hazard ratio of death.” — Peter Attia
I originally intended to introduce the entirety of this lever in one article. As its writing came to completion, the final product was far longer than I had anticipated. In an effort to increase retention of the content presented and to prevent information overload, I decided to split Lever #3: Exercise into three installments.
This week will cover some important introductory content as well as the first two sub-levers, aerobic and anaerobic exercise. The next article will cover strength, followed by a third post on stability, flexibility, and mobility.
Any exercise regimen geared towards longevity must address all four of its pillars or sub-levers. These pillars often interact with or are dependent upon one another and each is crucially important to extending our healthspan and lifespan. Not only will achieving a high level of fitness in each of these areas benefit us tremendously down line, but also in our day-to-day lives right now.
Becoming well-rounded in your fitness will allow you to interact with the world in a stronger, more fortuitous, and energetic manner. And, compared to the average of the general population, it’s not nearly as difficult a task to achieve as you may believe.
Exercise as a Drug
In a world where everyone is looking for a quick fix, a pill to solve all their problems, the world of exercise demands the opposite. To exercise means to practice commitment, dedication, and hard work on a consistent and perpetual basis. In other words, the requirement for exercise doesn’t cease until your heart does. This makes the need to find a way to enjoy the process, and not just seek some result, of utmost importance. However, devotion to a comprehensive exercise program will reward you handsomely for your efforts — much more than any pill can, a claim which I’ll support with research below.
A study that classified its 122,000 participants as having low, below-average, above-average, high, and elite fitness levels, based on their VO2 max, found massive reductions in mortality as a result of improving cardiorespiratory fitness. The results revealed that going from low to the below-average classification resulted in a 50% reduction in mortality over a decade and going from low to the above-average group resulted in a 60% to 70% reduction in mortality. Although the marginal benefit decreases when one goes from high to more elite fitness levels, there is still a measurable reduction in mortality that comes with achieving the best cardiorespiratory fitness possible.
This study is one example of how exercise can reduce our risk of mortality. Each of the four forms of exercise has its unique benefits, but they all share two key characteristics: 1) They decrease our mortality rate (often in different ways as each protects us from different causes of death) — meaning they increase our lifespan or length of life, and 2) They improve the quality of our day-to-day life, both now and especially as we age — meaning they increase our healthspan or quality of life.
The bottom line is that exercise decreases our risk of developing the conditions that kill the vast majority of U.S. adults, and Western adults in general, over age 40 (The Four Horsemen: atherosclerosis, cancer, neurodegenerative disease, metabolic disease, and a bounty of other killers including lung disease and frailty).
By becoming well-rounded and proficient with our exercise now, we have the ability to do the things we want to later on in life as we’ll have the strength, endurance, and stability required to do so. In a similar manner, it gives us the capacity to live better now by fundamentally improving the way in which we’re able to interact with the world around us.
The beauty of exercise, along with the four other levers of longevity, is that we get to play both the short- and long-term games simultaneously. The actions we take now will benefit us in the present moment, as well as 20, 40, and 60 years downline.
The Principle of Minimum Effective Dose
There’s little satisfaction to being in great shape if you don’t have the time to enjoy the benefits that come along with it. If your exercise routine demands that you spend three grueling hours a day in the gym, not only are you likely wasting your time with inefficient practices, but you’re missing out on other important parts of life such as spending time with loved ones, adventuring, trying something new or working on your favourite hobby. This is where the principle of Minimum Effective Dose (MED) comes to use.
The MED is simply the smallest dose that will produce a desired outcome. Anything done beyond the MED is wasteful. This is a concept I was first introduced to by Tim Ferriss in his book The 4-Hour Body. Determining the MED for each of the four sub-levers of exercise allows us to minimize time spent exercising while maximizing our results.
For each form of exercise, I’ll prescribe a MED based on what the current literature is suggesting. However, at the end of the day, action is better than inaction, and doing something is better than nothing. Start with what you can maintain sustainably and once you feel confident, add from there.
Aerobic vs. Anaerobic Exercise
We’re often taught that aerobic means our bodies are producing energy with the use of oxygen whereas anaerobic conversely means without oxygen. However, this isn’t the most accurate way to distinguish between the two since both functions take place in the presence of oxygen.
A more accurate way to differentiate these forms of exercise is by looking at the speed at which the muscle is demanding energy, scientifically known as adenosine triphosphate (ATP) which is the primary carrier of energy in human cells. Before arriving at an updated definition, it’s important to first understand the different energy systems which are used by the different types of muscle fibres. By looking at both muscle fibre type and energy system (cellular fuel) we can better determine what form of exercise, aerobic or anaerobic, our bodies are engaged in.
Muscle Fibre Type
There are two broad classifications of muscle fibre: Type 1 (slow-twitch) and Type 2 (fast-twitch). The speed does not refer to how fast the muscles twitch, but how quickly the fibres fatigue. Type 1 fibres contract less forcefully and, as a result, we’re able to perform aerobic activities that engage these fibres, such as jogging 10km, for a longer period of time. Type 2 fibres are further broken down into Type 2A and 2B, the difference between them being the predominant energy source used — a topic I won’t get into the details of in this article. In general, Type 2 fibres contract more forcefully and fatigue quicker making them useful for anaerobic activities such as a sprint or one minute maximal, but not much else.
Our two main fuel sources are fatty acids and glucose. While engaging in lower intensity aerobic activities, we predominantly use fatty acids as fuel. As exercise intensity increases so do energy (ATP) demands. This results in our bodies switching from the aerobic to the anaerobic system and from using fatty acids to using glucose as fuel since it’s a faster energy system. Put differently, in aerobic exercise, we predominantly oxidize fatty acids for energy while in an anaerobic state we metabolize glucose for energy.
A useful analogy is to think of a car with two tanks, one of which contains diesel fuel (fatty acids) and the other regular gasoline (glucose). When we’re driving a long distance, our car burns the fuel in the diesel tank, the fatty acids, since it’s more efficient and will perform better over a longer period of time. However, if we need a short boost of energy to make it up a hill or run a yellow light (not that I’m encouraging that), we switch over to the regular gasoline, the glucose, for that short but intense burst of force.
With a basic understanding of the different muscle fibres and our two main energy systems, we can now proceed with an updated definition of aerobic and anaerobic exercise. Aerobic exercise is that in which we are using Type 1 (slow-twitch) muscle fibres and predominantly using fatty acids for energy. On the other hand, anaerobic exercise engages Type 2 (fast-twitch) muscle fibres and mainly uses glucose for energy.
The importance of these definitions will become apparent as we introduce different training zones that best target these two systems from an exercise perspective.
Aerobic and anaerobic exercises are often classified by training zone, as seen in the chart above. Each of the six training zones corresponds with a predominant energy source and type of muscle fibre engaged.
Recall that fatty acids (fat) and glucose (carbohydrates) are the main energy sources that the three types of muscle fibres, Type 1, 2A, and 2B, burn. If you don’t know the difference between Type 2A and 2B, that’s okay. That discussion requires a more in-depth, scientific explanation which isn’t necessary for our purposes here.
Now, let’s dive into how to actually train our aerobic and anaerobic systems.
Sub-Levers of Exercise: Aerobic & Anaerobic
The aerobic system is associated with fat burning and all of the factors that play a role in the fat-burning process including the aerobic muscle fibres (Type 1), the mitochondria, and the ability to convert fatty acids into energy (ATP).
Zone 2 is the primary aerobic training zone and our target while performing aerobic exercise. Although there are different ways to determine whether we’re in Zone 2, the simplest method, and the one I recommend using, is by judging our rate of perceived exertion.
The talk test, or gauging your ability to hold a conversation while performing an aerobic activity, is generally a reliable indicator. This is how it works: Run (or insert your exercise of choice) at a pace where you are able to hold a conversation but would prefer not to. That is, if you can talk but would find it annoying to do so, you’re likely in Zone 2.
Another method to determine if you’re in Zone 2 is by measuring your heart rate. If you know your maximum heart rate, which is the highest your pulse can get, you can start by exercising aerobically at 75% of that figure and then taper up or down based on your ability to pass the talk test. Alternatively, you can estimate your maximum heart rate by subtracting your age from 220. However, since this calculation is often inaccurate and it can be dangerous to try and determine your maximum heart rate through exercise, I recommend sticking with the talk test.
It’s worth mentioning that the gold standard method of determining which training zone you’re in is by measuring blood lactate concentrations. I’m making the bold assumption that none of us have a blood lactate measurement device at home, so I won’t address this any further.
The minimum effective dose (MED) for Zone 2 aerobic training is ideally between 3-4 hours per week with 2 hours per week being a good place to start for beginners. If you’re a psychopath who can’t get enough aerobic training (no offense, I commend you), you have little to fear as you probably can’t do too much Zone 2 training.
One beneficial feature of aerobic training is that it can take on many diverse forms. The choice is up to you: run, swim, bike, dance, elliptical, stairs, jump rope, walk, or whatever else you prefer as long as you stay in that Zone 2 state for a total of 2-4 hours per week. If this seems like a lot, don’t let overwhelm result in inaction. Start with whatever you can manage on a weekly basis and build up as you see fit.
Any aerobic exercise is better than none and will have profound impacts on your heart health and overall well-being. One of the best things we can do to reduce our risk of heart disease is to engage in exercise that targets our cardiovascular system. Zone 2 training is an extremely effective method to do just that.
Anaerobic exercise consists of short bursts of intense activity with a period of rest in-between. As Zone 5 is our target training zone for this system, a common anaerobic training method is some variation of high-intensity interval training (HIIT). The amount of time that we spend in an anaerobic state is overestimated by most. As mentioned, unless we’re sprinting or doing a one-minute maximal (exerting our maximum amount of energy for a duration of one minute), we’re likely in an aerobic state.
Our Zone 5 training goal is to contract the muscle as fast, forcefully, and efficiently as possible. This can be done through HIIT workouts involving anything from sprinting, resistance training, burpees, stairs, rowing, and many other formats as long as the condition of exerting as much energy as possible for a short period of time, often less than one minute is met.
We don’t need to spend as much time in Zone 5 compared to Zone 2 and it can often be worked into our everyday lives. For example, instead of taking the escalator, sprint up the stairs as fast as possible or opt to haul your groceries up the stairs as quickly as you can instead of taking the elevator. This is also a good practice in not caring about what others think of you since you might look a little crazy sprinting up the stairs of your local mall.
Since your anaerobic system will likely be worked through strength training, which we’ll cover next week, and your day-to-day life, the MED for Zone 5 exercise is 1-2 focused sessions per week.
What’s your favourite way to train these systems? Let me know in the comments.
Run For Your Life
If anything resonates with you from this article, I hope it’s an understanding of the profound impact that exercise can have by improving our lives both now and in the future. It’s okay if you don’t currently train your aerobic and anaerobic systems, but I encourage you to think about all the ways, regardless of your age or starting place, that improving your cardiorespiratory health will benefit you.
Start small with whatever you can manage, but take action. It may be unpleasant at first, but I’m willing to bet you may even get hooked once you begin to feel better in your everyday life whilst having the knowledge that taking these actions now is reducing your risk of all-cause mortality in the future.
Next week we’ll complete our introduction to exercise by gaining an understanding of strength and stability, flexibility and mobility, the final two sub-levers of exercise.
And, as always, please give me feedback on Twitter or by hitting reply to this email.