Learning log #3: Aerobic Endurance and Strength
“Learning Log” is a series where I share what I learn. In a previous post, I discussed the idea of aiming for the The Centenarian Decathlon—the 10 things we want to be able to do irrespective of our age—as we think about the different tactical knobs we have in our control—Exercise, Nutrition, Sleep, Emotional health and Supplements.
In this post, we will dive deep into the first knob: Exercise
Instead of aiming for a specific goal (like, a marathon), the exercise regimen discussed here aims to optimise for longevity. Specifically, to delay the onset of chronic diseases and death while maintaining our healthspan for as long as possible.
Healthspan = Of the years we live, how many of them do we remain healthy and disease free in
We must focus on optimising 3 dimensions of fitness:
Aerobic endurance: Cardio refers to a physiologic continuum, from an easy walk to an all-out sprint. We care about 2 specific regions on this continuum:
long, steady endurance work (like, jogging, cycling, swimming) where we train in Zone 2 (explained later)
maximal aerobic efforts where VO₂ max comes into play (explained briefly in the previous post but described in detail later)
Strength: The fundamentals of how to grow muscle is simple. If we use our muscles to counter some resistance, in the form of weights or other forces (e.g. gravitation), they will adapt and grow stronger. Here, we care about both muscle mass and muscle strength.
Stability: While we train for the above two, we need to avoid injury in the process. This is where stability comes. It creates a solid foundation that enables us to do everything else. We must aim to increase our resistance to injury.
As the title suggests, we will only discuss 2 of these in this post because stability is a beast of its own that deserves a separate post, primarily because I knew so little about it.
Aerobic Efficiency: Zone 2
Instead of thinking about burning calories, we will view exercise in terms of fuels—specifically, glucose and fats. How we utilise them is key to fitness along with metabolic and overall health.
Mitochondria
Mitochondria is central. It is called the powerhouse of a cell as it is the place where all the energy in a cell is produced. Here is why it matters:
It can burn both glucose and fat (the only place in our body where fat can be converted to energy)
It is fundamental to our metabolic health, athletic performance and maintains brain health
It helps control bad actors like oxidative stress and inflammation
A healthy body needs a healthy mitochondria, which is where Zone 2 training comes in. But what does “Zone 2” even mean?
What is Zone 2?
Zone 2 is one of several levels of intensity used by coaches in endurance sports to structure the training programs for their athletes. Practically, it translates to aerobic activity at a pace somewhere between easy and moderate. We will make this more specific shortly.
Zone 2 is foundational as it builds a base of endurance for anything we want to do in life. Fat is our body’s most efficient and abundant fuel source. But fat accumulation and spillover drives conditions like diabetes and cardiovascular disease. Typically, someone working at lower relative intensity burns more fat whereas one working at higher relative intensity burns more glucose.
The ability to burn both fuel sources is called metabolic flexibility and we want that. The healthier and more efficient our mitochondria, the greater our ability to burn fat and lower the risk of chronic diseases.
Why does Zone 2 vary for different people?
Every person, depending on their fitness level, has a different Zone 2. The Zone 2 (low-moderate intensity) for a professional cyclist might be the Zone 5 (very high intensity) for a sedentary person. But why is that?
When we operate in Zone 2, we utilise our type 1 (or “slow-twitch”) muscle fibers, which are dense with mitochondria and hence, suited for slow, efficient endurance work. But if we increase our pace, we start recruiting our type 2 (or “fast-twitch” muscle fibers) which are less efficient but more forceful. They also generate more lactate because of how they produce energy. This lactate pairs with hydrogen ions to produce lactic acid which is responsible for the acute burning sensation that we feel during a hard effort. Lactate is super important and it literally defines Zone 2. Another, more specific, definition of Zone 2 is the maximum amount of effort we can maintain without any net increase in lactate, i.e. the amount of lactate being produced is equal to the amount being cleared away by the mitochondria.
The more efficient the mitochondria, the more lactate gets cleared away and hence, the more effort we can sustain in Zone 2. Hence, someone with a healthier and more efficient mitochondria has a different Zone 2 than a sedentary or mildly active person.
How to detect if we are in Zone 2?
There are many different ways:
Keep a lactate monitor—our lactate levels should be between 1.7-2 millimoles. But most people won’t do this. So, let’s consider more practical options.
Measure our heart rate. In Zone 2, our heart should be somewhere between 70-85% of the maximum heart that we have ever recorded on a heart rate monitor.
Rate of Perceived Exertion (RPE) or the “talk test”: We should be able to speak but not interested in holding a conversation.
Consequence of an unhealthy mitochondria
Those with unhealthy mitochondria quickly switch from aerobic respiration—burning fat and glucose in the mitochondria with oxygen—to the less efficient glycolysis—the energy producing pathway that consumes only glucose and produces a lot of lactate, making the effort quickly unsustainable. Those with less efficient mitochondria also have much higher resting lactate levels, meaning that their mitochondria is already working too hard just to maintain baseline energy levels. This means that they rely primarily on glucose as their fuel source to meet their energy needs and are unable to access their fat stores.
Thus, those who are most in need of using their fat stores as a fuel source and who have an abundance of it are unable to tap into it while the healthiest ones are able to do it very easily due to their metabolic flexibility.
A significant marker of aging is a decline in the number and quality of our mitochondria. But it is plastic. With aerobic workouts, we can stimulate the creation of new, more efficient mitochondria while getting the dysfunctional ones recycled out. But if we don’t use them, we will lose them.
How exercise helps fight chronic diseases
Muscle is the largest storage sink for glucose. By increasing our mitochondria, we increase our capacity for converting it to fuel instead of having glucose end up as fat or in our blood. Chronic blood glucose elevation wreaks havoc in the body. The glucose uptake while exercising is 100 times more than when we are at rest. Typically, a hormone called insulin mediates the glucose uptake. When the body detects a rise in our blood glucose, our pancreas secretes insulin which prompts our cells to absorb glucose from the bloodstream, helping moderate the level of blood glucose. During exercise, another pathway is also used to facilitate this glucose uptake, one that transports glucose directly across the cell membrane without insulin being involved (non-insulin-mediated glucose uptake or NIMGU). This is why exercise can be very effective in managing both type 1 and type 2 diabetes.
Type 1 diabetes: when the body is unable to produce insulin altogether
Type 2 diabetes: the body develops insulin resistance where even though insulin is being produced, it does not promote the glucose uptake described above, leaving our blood glucose levels elevated
Through NIMGU, one can bypass the insulin resistance to bring down the blood glucose levels purely by exercising and those with type I diabetes can get by with injecting much lesser insulin into their body.
Zone 2 also improves cognition by increasing cerebral blood flow and stimulating the production of BDNF (brain-derived neurotrophic factor) which keeps our hippocampus healthy, the part of our brain that plays a key role in memory. This is why it is important for the prevention of brain-related disorders like Alzheimer’s and dementia.
Protocols
For a sedentary person, it is very easy to start training in Zone 2. Brisk walking might be enough. As one gets fitter, they need to increase the intensity (maybe start jogging) to get into Zone 2.
There are many ways: cycle/walk/jog/swim/run. The key is to find something that fits our lifestyle and we enjoy doing.
Two 30-minute sessions per week is a good starting point. But in steady state, around ~3 hours per week (or four 45-minute sessions) are a minimum for people to derive a benefit and make improvements.
Some machines let us measure the power output of our Zone 2 workout. 2 watts/kg is a good number for a reasonably fit person, 3 watts/kg for a very fit person and 4 watts/kg for professional athletes.
Maximal Aerobic Output: VO₂ max
A VO₂ max effort is at the opposite end of Zone 2. It requires much higher intensity, often only for a few minutes, but still short of an all-out sprint. At VO₂ max, we use a combination of aerobic and anaerobic pathways to produce energy but we are at our maximum rate of oxygen consumption. Oxygen consumption is the key here.
How is it measured?
Measuring VO₂ max is an unpleasant experience as it requires running on a treadmill at a very high intensity while wearing a mask designed to measure oxygen consumption and carbon-dioxide production. The peak amount of oxygen we consume, typically close to the point at which we just can’t keep going, is called VO₂ max.
Why does VO₂ max matter?
It is strongly correlated with longevity.
VO₂ max is a good proxy measure of our physical capability.
It declines steeply with age (roughly 10% per decade, upto 15% after the age of 50) and this decline corresponds to diminished functional capacity. What seems easy when we are young or middle-aged becomes difficult (even impossible) as we age.
It is important to understand the gravity of this. A moderately fit 35-year old (VO₂ max in the mid-thirties) will be able to run one mile in 10 minutes. But by the age of 70, only the fittest 5% will be able to do so. This can similarly be extended to the different kinds of activities listed in the chart above.
Improving VO₂ max by any amount will increase both our lifespan and our quality of life. Going from the very bottom quartile of performance to the next quartile reduces all-cause mortality (death due to any cause) by 50%.
Goal
The more active we want to be as we age, the more we have to train for it now.
Train for as high a VO₂ max as possible. Ideally, we should aim to be in the elite range for our sex and age.
Once we are there, we should aim to get into the elite range for 1 decade younger, and so on.
It is never too late to improve our VO₂ max. It will be hard work over a long period of time. Longer and more focused training can yield large gains over an extended period of time (years, not weeks). We have to think of this as a lifelong project.
What most of us really need in our aerobic fitness is the ability to go slow for a long period of time (Zone 2) while being able to go hard and fast when needed (VO₂ max).
How to train VO₂ max
While Zone 2 training automatically increases one’s VO₂ max, increasing VO₂ max requires separate training of its own, typically introduced 5-6 months after steady Zone 2 work.
High Intensity Interval Training (HIIT) intervals are very short (seconds). VO₂ max training ranges from 3-8 minutes and are slightly less intense. One can use either a stationary bike or a rowing machine or a treadmill. A single workout per week focused on VO₂ max is often enough.
What a single workout session should look like:
~4 minutes at the maximum pace that can be sustained for this duration of time; not an all-out sprint but still a very hard effort.
Then, take it easy for 4 minutes for the heart rate to come down to ~100 beats per minute. It is super important to be fully recovered before beginning the next set otherwise we won’t be able to give it our best and won’t get the desired adaptation.
Repeat this for 4-6 times.
We must give ourself enough time to warm up and cool down from this intense effort.
Strength
Our muscle mass begins to decline as early as our thirties. Our muscle strengths declines 2-3 times more quickly. We lose power (strength x speed) 2-3 times faster than strength. This is because as we age the biggest change in muscle is the withering away (“atrophy”) of our type 2 (“fast twitch”) muscle fibers. This is why our exercise regimen must be aimed at improving these by heavy resistance training.
Zone 2 + VO₂ max => prevents the atrophy of type 1 muscle fibers
Resistance training => prevents the atrophy of type 2 muscle fibres
The curse of inactivity
It takes a much longer time to gain muscle mass and strength than to lose it. Even a short period of inactivity can cause significant loss. This is another reason why preventing injury is very important as that can cause a long period of inactivity.
Inactivity is dangerous. Period.
Being sedentary + consuming excess calories is a recipe to accelerate muscle loss as one of the prime targets of fat spillover is muscle. This excess fat accelerates muscle loss through many ways—chronic inflammation which interferes with protein synthesis and accelerates muscle breakdown, insulin resistance, resistance to muscle-building activities and disrupting the stimulation of testosterone and growth hormone.
Muscle loss, in its extreme form, is called sarcopenia. Someone with sarcopenia has:
low energy
feelings of weakness
problems with balance
Sarcopenia is also a prime marker for a clinical condition called frailty, where a person meets at least 3 of 5 criteria:
unintended weight loss
exhaustion
low physical activity
slowness in walking
weak grip strength
At this stage, it becomes very hard to increase muscle mass and strength.
Bone Mineral Density (BMD)
Another metric to track is bone mineral density (BMD) which follows the same trajectory as muscle mass described above. The decline is more severe for women after they hit menopause as estrogen is essential for bone strength in both men and women. Why this matters is the same reason as muscle—protection against injury and frailty—and should be checked every few years.
Instead of intervening after the damage has been done, the idea is to intervene early. Hence, if low or declining BMD is detected in a middle-aged person, we can apply one of the following strategies:
Optimise nutrition, focusing on protein and total energy needs
Strength training, especially with heavy weights, stimulates the growth of bone more than impact sports like running/cycling/swimming.
Hormone Replacement Therapy (HRT) for women who have entered menopause, if needed.
Drugs to increase BMD, if needed.
Strength training as retirement saving
Strength training is like retirement saving in 2 ways:
We want to enter old age with a surplus of muscle so that it can protect us from injury and allow us to continue doing whatever we want to do.
It compounds over time. The more we build up early on, the better off we will be in the future.
The comfort crisis
Unlike what most people believe, strength training is not about bigger biceps. It is largely about improving our ability to carry things. This was introduced in the book, The Comfort Crisis, where the author explains how we have removed all discomfort from modern life which has made us lose touch with the fundamental skills that once defined what it meant to be human. Carrying things over long distances is one such skill. Our ancestors had to go far and wide to hunt for food and carry their kills back to their camps to feed everyone. This gave them robust functional strength and endurance which was very protective.
How to train for strength
Rucking
One way to bring carrying back into our lives is through rucking, which means hiking or walking at a fast pace with weights tied to our back. It can be improved further by avoiding carrying phones to give us a chance to be just with us, the nature or a friend. A good goal to aim for is being able to carry 25-33% of our body weight we develop enough strength and stamina. If we have the chance to go up and down an incline (e.g. a hill), it can help push our VO₂ max.
In general, to improve our strength, our training needs to be structured around the following as they are the most relevant to living a fulfilling and active life as we age:
Grip Strength
Attention to both concentric and eccentric loading
Pulling motions
Hip-hinging movements
Grip Strength
If we can grip strongly, we will be able to open a jar with ease in our later decades. Most people don’t think about training their grip strength—how hard one can squeeze something with one hand. But it is strongly linked to how long we live and low grip strength in the elderly is considered to a symptom of sarcopenia. It acts as a proxy for overall muscle strength, general robustness and the ability to protect ourself from a slip or fall. It is important at all ages.
Our grip is our interface with the world. If it is weak, everything else is compromised.
Training
1. Farmer’s carry
Walk for a minute or so with a loaded hex bar/dumbbell/kettlebell in each hand
A tougher version of it is shown below:
Goal: being able to carry half our body weight in each hand (full body weight in total for men [75% for women]) for at least 1 minute. We won’t be able to do it when we start training and will probably need to begin with far lesser weight, working up from there. That is perfectly alright.
It is more important to learn and practice ideal movement patterns than pounding heavy weights in a way that can cause injury.
The most important tip here is to keep the shoulder blades down and back, instead of pulled or hunched forward.
2. Dead-hang
Grab a pull-up bar and hang on to it for as long as we can, supporting our body weight.
Goal: 2 minutes for men and 90 seconds for women at the age of 40 (the goal is reduced slightly for each decade after).
Concentric and Eccentric loading
The concentric phase of a movement is when the muscle is shortening whereas the eccentric phase is when the muscle is lengthening, as shown below.
Focusing on the concentric phase and doing it slowly comes intuitively to us but most of us would struggle if we are asked to focus on the eccentric phase. As we age, eccentric strength is where most people falter. It is very important for protecting us from falls and orthopedic injuries. For example, eccentric strength in our quadriceps helps us control our movement as we walk down the stairs.
Eccentric loading also prevents our joints from taking up too much stress, especially our knees. The difference in force transmission to our joints when we are able to load eccentrically versus when we are not is huge.
Training
Relatively simple: focus on the “down” phase of our lifts. This video will help:
Don’t need to do it for every set (sometimes we just want to move quickly or move a heavier load) but we must make sure to take some time to focus on this in each workout.
Pulling motions
Pulling is how we exert our will on the world. If we can pull, we can carry groceries and lift heavy objects. It is closely related to grip strength.
Training
Rowing: This is where we pull weights toward our body
We can use a rowing machine as well:
Pull-ups
Hip-hinging movements
For these movements, we bend at our hips.
REMEMBER: we should not bend our spine.
They allows us to harness our body’s largest muscles—glutes and hamstrings.
These movements are critical to life. For example, when we get up from a chair or try to pick up something we dropped, we are doing a hip hinge.
Training
Hip hinging with a heavy load (for example, during a deadlift or a squat) comes with an injury risk.
We can start with single-leg step ups and split stance Romanian deadlift (either without weights or very light weights).
Check out the Step Up tutorial by Peter Attia here!
Work up to heavier weighted hip-hinging very slowly.
Throughout the post we touched upon the importance of preventing injury. This is where stability comes in, which will be the focus of the next post. Hope you learnt something interesting. Till next time.
🤌💪🔥🗿