Category Archives: The aerobic system

It’s almost impossible to do an “easy workout” when you’re stressed.

A while ago I read an excellent article titled Why heart rate always matters. It goes into great detail on a topic I’ve previously discussed here on running in systems: why the heart rate is always going to be an excellent representation of what is happening with the body’s stress response and energy metabolism. I think that some of the topics it discusses, as well as the excellent debate in the comments, are worth expanding on. Here’s an excerpt from it:

“Our fight-or-flight system often activates without any actual demand. When we get ‘stressed out’–engaged in a heated argument, mulling over a burdensome worry, or simply sitting in traffic–seldom is any physical task being undertaken. But the body is being activated. The engine is revving higher and tremendous sugar–the preferred fuel of fight-or-flight responses–is burned when under psychological stress, which is a major factor in ‘stress eating!’ We function as if we’re fighting an intense battle.

Stressed out and going for a run? Your body will perceive the cost of that run as higher (because it is already dealing with your life stress) and will activate a more intense energy system to cover all the demands. More energy cost!”

There was a particular comment in the article that I wanted to address:

“Very well written article and I agree with most of it.
However, I think you overstate the impact of activation level on energy expenditure…

…In my understanding, the energy demand dictates the energy production. And the energy demand is mainly dictated by the mechanical work of the muscles and all the side processes needed for that level of power output.
I agree, that the excitation level directly impacts the chosen energy supply system but as long as this system doesn’t actively provide energy, it’s [maintaining] cost will be relatively low.
Yes, a higher activation will have a higher energy demand but I don’t believe it’ll come anywhere close to exceeded mechanical [energy] demands.”

I agree with the commenter in that I, also, believe that the author was overstating the impact of activation level on energy expenditure. However, I think the author’s overstatement makes it difficult to observe 2 key implications of this discussion:

  1. Activation level  (a.k.a. stress) changes the type of energy metabolism, which means that it changes the ratios of fuel (fat and sugar) that it uses.
  2. Training stimulus is inextricably tied to activation level and energy metabolism. This means that the ratios of fuel usage have a much bigger say in how the body perceives the workout (as low-intensity vs. high-intensity) than the rates of fuel usage.

The point is that while the author does overstate the energy cost of the stressors he mentions, it doesn’t really matter—there’s things the athlete just can’t get out of training if their body is taxed in the ways the article mentions.

A lot of people think that low-intensity means “slow,” “easy,” or “consuming little energy.” It doesn’t. Low-intensity is when the workout is easy on the body—specifically, when the body is burning a majority of fats for fuel, and the sugar that is being utilized is burned wholly aerobically  (in the presence of oxygen). In other words, there is no substantive anaerobic work. Highly-trained endurance athletes, who burn fats at much greater rates than the rest of us, can run at very high speeds while remaining in a completely aerobic state. Such an athlete may be running blazing times in a workout that is for them, metabolically speaking, a low-intensity workout.

Now let’s look at higher intensities: In order to produce the energy necessary to approach your top speed, a lot of changes have to happen within the body. One of these is that the body has to go from burning a greater percentage of fats (which burn relatively slowly and so provide energy at a relatively lower rate), to burning a greater percentage of sugars (which burn relatively more quickly and so provide energy at a much faster rate). So, in order to get closer to your top speed, a greater percentage of your energy has to come from sugar.

In order to release more sugar to the bloodstream (to be utilized by the muscles), the body releases hormones called glucocorticoids—glucose (a.k.a sugar) releasing hormones. The main glucocorticoid is cortisol, which many will recognize as the main stress hormone. Another hormone that is release during the stress response is insulin, which helps muscle cells avail themselves on the sugar that cortisol released into the bloodstream. Cortisol and insulin, then, work synergistically to produce (and increase) sugar metabolism.

To recap: want to run closer to your top speed? You need to release more sugar. How do you do that? By getting more stressed. But because of some of the body’s more complex molecular mechanics—fodder for another post—the body can’t release a bunch of sugar and still be releasing fats. What would happen is that you’d just flood the bloodstream with unhealthy concentrations of both fuels. So, when insulin is released or when anaerobic function (which is dependent on sugar) increases, fat-burning drops. If sugar-burning goes up, fat-burning goes down (and vice versa).

This works the other way around too. If you get more stressed because, say, you had a rough day at work, or you got into an argument, you’ve got more cortisol and insulin running through your body. But it’s not like the body can decide to release (and use) sugar only when the reason for cortisol and insulin release is because of increased athletic demand (a.k.a. athletic stress). For any other stress (work stress, etc.), cortisol and insulin become released, and increase carbohydrate metabolism. Research on the metabolic effects of social stress in fish supports this idea.

This, incidentally, is why people get tired after a stressful day at work or an argument that stretches for too long. They didn’t use up all their fat-stores at work, obviously. But because the stress put them in sugar-burning gear, enough of their sugar ran out that they start feeling tired. It’s not that they ran out of fuel, but rather that they ran out of the fuel they’ve been stuck using.

It also takes a relatively long time for the cortisol to get out of your system—and when it does, it’s not like you can just pop back into action and go for a run. The adrenal glands, which put out cortisol (not to mention various other mediators of the stress response) have been used up. They’re tired, and will resist further activity. And since you use all the glands in the body to one (significant) degree or another during training, it’s not a good idea to train with exhausted or depleted glands.

Asking your body to work out when you’re already out of a major fuel and your stress glands are tired is an even worse idea: the “same” workout is relatively much harder for a tired gland that’s nearly out of adrenaline and cortisol than for a rested gland. Training after a period of stress is, in physiological terms, almost exactly like doing back-to-back training sessions. Effectively, you’re extending the period of stress.

And if on top of that, your blood sugar is low (as usually happens after a period of stress), you’ll be asking those tired glands to produce even more cortisol and adrenaline than they would usually have to: in their already tired state, it’s not enough to simply produce enough cortisol to maintain blood sugar levels—they have to make up for the lack of sugar in the bloodstream.

If on top of that, you’re “stuck” in sugar-burning mode because you still have all that errant cortisol and insulin flowing through your system (since you’re still stressed), you’ll be depending on sugar—which you’ve substantively burned through—for the duration of your training session. Because the body is inhibited from fueling itself with fats (due to the insulin in your system), it has to rev up those exhausted adrenals even more to provide the requisite cortisol.

Insofar as your body is stressed, it will respond to what is normally an “easy” workout as if it were a “mini high-intensity workout.” In other words, you can’t really have a “low-intensity training session” when you’re stressed (and expect to accomplish your goals in any sort of way). 

This is why doing MAF training—exercising under the aerobic threshold—under stress (or after a period of stress) produces such a dramatic drop in speed/power output at the same heart rate. When you’re under stress, exercising at a rate that looks anything like the aerobic training you do when unstressed would mean elevating your heart rate far beyond your aerobic threshold. Because aerobic work output is so reduced in a stressed state, it’s a much better idea—and a much simpler fix to the problem—to simply rest for the day and do your “easy” training session tomorrow.

What the hell is the aerobic system? Part 1

Frequent readers of my blog know just how much I like to use car metaphors to describe the human body’s function. So here’s another one: the aerobic system is the body’s main powertrain.

(The powertrain is the chain of systems within the car that power gets channeled through: from the engine, through the gearbox, down the main drive shaft, across the differential, and into the wheels. The drivetrain on the other hand is typically understood as the powertrain minus the engine.)

When most people think of increasing aerobic function, they think of increasing the capabilities of the body’s aerobic, Type I muscle fibers (also known as slow-twitch fibers). While muscle fibers are hugely important—they are the main power producers of the body—they are one subsystem of many that need to be working synergistically and at similar rates for the aerobic system as a whole to be able to express any kind of power.

It’s important for us to realize that when we are talking about developing the aerobic system, we are talking about much, much more than just the aerobic muscle fibers themselves. Quite literally, the whole powertrain from beginning (lungs) to end (muscle fibers) needs to work and develop together for it to be of any use.

The body, unlike the car, stays on all its life. The car can shut off if it runs out of fuel. But if the same thing happens to the body, it dies. So any system that is going to take on the responsibility of being the body’s main powertrain has to be able to provide a stable flow of energy over a very long term.

The best way to accomplish this is by burning a cheap, safe, light, efficient, and plentiful fuel source: fats. (As I’ve discussed before, burning carbs/sugar comes with a lot of strings attached: it’s dirty, heavy, scarce, inefficient, addictive, and dangerous. The only real advantage it has—and it is a BIG advantage—is that it produces energy at a much greater rate than fats.)

Being the system that provides stable, long-term energy means that you need to burn the stable, long-term fuel. Because of this, the aerobic system has to burn fats in particular as its primary fuel.

In other words, I use Phil Maffetone’s rendition of what the aerobic system is. This means that while I like statistics such as VO2Max (maximum volume of oxygen utilization per minute) as measures of aerobic power, I don’t believe they are a measure of the functionality of the aerobic system. Why? Because you can consume far more oxygen when you’re burning sugars than when you’re burning fats. And besides, we’ve defined the aerobic system as providing energy over the long-term. Therefore, aerobic functionality has to do far more with fat-burning, which occurs in a big way at moderate percentages (55-65%) of VO2Max, than with sugar-burning (which occurs in a big way at 65-100% of VO2Max).

(Note that very highly-trained endurance athletes are often an exception to these percentages. Why that’s the case is for another post.)

One of the reasons this system has the name “aerobic” is because fats cannot be burned outside of the presence of oxygen. So, bringing oxygen into the body and enabling its efficient transport throughout is absolutely essential to our capability to use fat as fuel. In fact, this is one of the most important differences between fat and carbs: carbs unlike fats, can be burned both aerobically and anaerobically.

This may seem like an advantage, but it’s somewhat of a disadvantage—in the same way that the disadvantage of cocaine is how powerful it is. You’re far better off experiencing the feeling of reward in the less powerful, sustainable, and old-fashioned way.

This is not to say that sugar has no place in our utilization of energy: at any given point in time when we’re at rest or doing light activity, we’re burning a small percentage of carbs. But when sugar stops being your auxiliary fuel (and becomes your go-to fuel), you’re in trouble.

By primarily using a fuel that is very powerful, it’s much easier to use only that fuel. Why would you use the other, less powerful fuel? (Sure, because it’s lighter, cleaner, safer, and more efficient.) But there’s also this: since carbs burn way quicker, the body can get lazy and forget about maintaining its fat breakdown and transpo systems, with little short-term negatives—but huuge long-term drawbacks.

By the time that the downsides of relying primarily on sugar begin to roll around, the body is hooked and the systems that burn and transport fat are in utter disrepair. The body can only store about 2,000 calories of carbs at a time (compared with some 120,000 calories of fats on the low end). When it prefers sugar over fats, it has to be eating all the time.

In layman’s terms, this is known as a “metabolic SNAFU.” (That acronym fits particularly well here, just because of how ubiquitous and “normal” this situation is.)

So what are these systems? Let’s trace the flows of oxygen and fats to find out.

Fats have to be broken down from fatty tissue, transported through the blood vessels, and burned by the mitochondria—the cell’s aerobic motors.

Oxygen comes into the body through the respiratory system, then gets transferred to the circulatory system, and finally permeates into the muscle cells where it is used as a reactant to convert the fats into energy.

But if we’re going to talk about flows of materials (oxygen and fats), it’s not enough to just discuss the parts that they flow through (and the systems that convert them into energy). We have to talk about the parts that regulate those flows, for the simple reason that if those regulatory systems stop working, chaos ensues. So these regulatory systems are as critical to the function of the aerobic system as, say, the car’s computer is to the function of its powertrain. It’s a part of it, pure and simple.

Let’s look at oxygen.

As any asthmatic or person with hay fever will tell you, those regulatory systems make a difference. The reason a lot of people start wheezing when they run too hard for too long is because the part of the nervous system responsible for increasing the body’s activity levels (known as the sympathetic nervous system, or SNS) gets too tired, and its function collapses. A crucial part of increasing activity levels is to open up, or dilate, all of the body’s ducts (a.k.a the airways and blood vessels) so that more stuff can flow through, at a faster rate. So, when the SNS becomes exhausted, its ability to keep the airways dilated goes away. Its opposing system—the parasympathetic nervous system, or PNS, whose job it is to shut the body down—takes over. One of its jobs is to constrict the airways—and so they close up (hence the wheezing).

Regulation of fat-burning functions in a very similar way. The system most directly responsible for regulating fats is the endocrine (a.k.a. hormonal) system, affecting primarily (and IMO most critically) whether or not, and at what rate, fats are broken down. This process is known as lipolysis: lipo = lipid (fat); lysis = breakdown.

Lipolysis is accomplished partially thanks to a hormone called leptin. In healthy humans, leptin exists in the bloodstream in a big way only when the body is at a reasonably low level of stress. So, one of the reasons that fat-burning starts going down at an exercise intensity even slightly over moderate—which is known in the biz as the AerT or aerobic threshold (go figure)—is because the increase in exercise intensity puts out stress hormones that inhibit the activity of leptin. As exercise intensity increases beyond the aerobic threshold, lipolysis begins to slow down.

So it doesn’t really matter if the muscles have a whole bunch of mitochondria that were developed by training at a high intensity (remember: a.k.a. stress), and burning lots of sugar in an aerobic way. If the body’s lipolytic systems haven’t been trained, it’s going to burn very, very few fats during exercise. So it doesn’t really matter what’s going on in the muscles. Muscles (even aerobic muscles) get really big really fast and their ability to consume fuel increases very quickly—but the rate of lipolysis takes much longer to improve.

The rate at which the body is capable of breaking down fats (rather than the rate at which it can burn them, or the rate at which oxygen can be supplied) is typically the bottleneck. And that’s why “fit” people all too often manage nary a shuffle when they start running under their aerobic threshold: they’re sugar-burning beasts, but under the AerT the hormones are optimized for burning fats, not sugar. Those powerful muscles they have? They’re being fed fats with a teaspoon.

And one of the reasons it feels so slow is because they’re exercising at a relatively small percentage of their oxygen intake and transpo capacity. Why? Because they’ve trained it primarily in concert with their sugar-burning system. Their fat-breakdown system needs to become waaay stronger before it’s going to break down fats at a rate that is challenging or even meaningful to their present oxygen transpo capabilities.

Understanding which systems comprise the aerobic system is far less important than grasping the point that the aerobic system really is the entire powertrain. It’s far less critical to know whether your car has a carburetor or a fuel injection system, than to know that you should consider how the entire powertrain (and the car as a whole) is going to behave when you decide to upgrade some particular component.

If you’re going to swap your L4 engine block from with a V8, you also have to swap out the fuel pump and a host of other systems (not to mention the entire chassis)—or you’re going to end up with a V8 engine getting fuel at a rate meant for an L4. The understanding that you need to go look at the whole picture, instead of just at the muscle fibers (or whatever)—will inevitably take your search in the right direction.

There’s a bunch of other parts of the aerobic system left to cover. In my next post I’ll talk more about how the fat-burning process goes down and why it’s impossible to burn more fats when the rate of sugar-burning goes up. I’ll also get more into why the body is wired to rely more on sugar as stress levels go up (hint: because sugar burns faster). In later entries I’ll talk about how the various other parts of the aerobic system interact with each other, and why aerobic function can really only be developed and optimized at relatively low levels of exercise intensity.

Strategizing Stress, Part 1

Training, like life, is a messy business.

I say this because lately I’ve been working with two excellent models of athletic training, Pose Method and MAF. Writing about them is the easy part. Applying them is more difficult. I recently ran across a very interesting case of a Pose/MAF enthusiast who wants to develop an aerobic base according to MAF principles, but has to sacrifice the correct form (a.k.a. running Pose) to do so.

(And ends up getting plantar fasciitis in the process.)

However, just because you get plantar fasciitis when you run at an aerobic intensity—which for most people means “running slowly” (OK, very slowly)—does NOT mean that you get to skip building an aerobic base. Building an aerobic base is important. And to ensure any sort of long-term well-being (particularly as an athlete), it’s necessary. One of the key functions of the aerobic system is to buffer and absorb the stresses induced by high-intensity activity.

In order to develop a good aerobic base, it’s important to stay at a low intensity. According to the MAF Method, the point at which you get the most bang for your buck out of aerobic base building is just under the MAF Heart rate (what researchers refer to as the “aerobic threshold”).

But a certain amount of energy is necessary to maintain good running form. If the aerobic system can’t provide enough energy, then your body has to work harder (increasing the intensity) and recruit the anaerobic system to provide the rest. When the aerobic system becomes relegated to its auxiliary function—processing the by-products of anaerobic exercise (lactate and hydrogen ions)—it will begin to break down. Two strategies help protect its health:

  • Allowing it to rest between periods of high-intensity activity.
  • Creating opportunities for it to be the main provider of energy for exercise.

So, when someone has to forgo the period of low-intensity training that we typically term “aerobic base training,” it becomes very important to strategize the stresses of exercise. On the metabolic side, running slow isn’t worth the plantar fasciitis it’ll create (in this case). And on the biomechanic side, we have to be careful that the stresses of running at a higher intensity don’t exceed what an untrained aerobic base can handle.

A safe way to do this is by taking a hybrid approach:

Combine 2-3 days a week of relatively easy Pose training (running+drills) with 2-3 days a week of walking, jumping rope 5 days a week anywhere from 5-15 minutes. While this isn’t really aerobic base training, it is still a way to develop (or at least maintain) aerobic fitness while taking steps to remain injury-free. While the Pose training is “higher intensity,” there are two options for how to manage it correctly:

  • Keep sessions short (read: fatigue-free) and high-intensity (threshold pace and above).
  • Do longer (also fatigue-free) sessions below the anaerobic threshold.

In regards to aerobic training: even if you walk quickly, you’re unlikely to come close to your MAF HR. However, you’ll still be able to develop aerobically at a slower pace. A better option, if you have the means, is to go doing moderate hiking with your heart rate monitor, which should put your heart rate a little bit closer to MAF, for the most part. I myself happen to have trails 5 minutes away from my doorstep (downtown!), but that isn’t the case for most of us.

Jumping rope will get your heart rate closer to MAF than walking. Another benefit is that it helps you train one of the key components of running: the Pose. The Pose is that snapshot of the running gait where one foot is on the ground, the other is passing under the hips, and the body is in a slightly S-shaped stance.

By jumping rope—or even better, (a) jumping rope while alternating feet or (b) doing simple Pose drills in the process—it’s possible (for a lot of us) to train the running Pose without going over the MAF HR. (Remember: trying to maintain the running Pose was the initial reason for exceeding MAF.) But after having practiced the running pose under the MAF HR, it’ll take comparatively less aerobic base training to be able to produce the running Pose at the desired, low-intensity heart rate.

How long will it take to develop an aerobic base that’s good enough to maintain a running Pose throughout a run? It really depends on the person: their metabolic and biomechanical starting point, lifestyle, and devotion to their pursuit of athleticism.

 

Running form and aerobic training

Training at a low intensity—often referred as “aerobic training”—is extremely important to allow the body a respite from the stresses of high-intensity training, and to develop the mechanisms that increase its resilience. We know that much.

But when training aerobically is our only focus, even during a period of “aerobic-only” training such as base-building, we may be hindering our improvement: improving our running form, by reducing the difficulty of running, also reduces the stress on our body. Because stress suppresses the function of the aerobic system, taking the time to develop our form hastens our aerobic gains.

The standard set by The Pose Method is the best example of “good running form,” as I see it. I fully adhere to the notion that pursuing a standard—the right standard—of running form is the quickest and surest way to reduce the difficulty and stress of running. But I also believe we don’t need to go as far as mastering the tenets of The Pose Method to reduce stresses and bolster our aerobic training.

This is because of a concept called “power leaks.” Running is all about moving the center mass of the body forward in a straight line. Some vertical and horizontal oscillation can’t be gotten away from. However, minimizing that up-down and side-to-side movement lets more of the body’s energy to go towards moving it in a straight line, and removes the need to spend energy balancing the body’s odd movements.

Power leaks, in essence, are those jerky movements that happen in odd places of the body—a sharp outward rotation of the knee combined with an upward collapse of the hip, which causes the weight of the body to fall to the outside. The body then has to recover, shifting its weight back in, to produce the next step.

When this extraneous weight shift and joint movement happens, the force of the footstrike travels through the body at an odd angle. Muscle fibers, and tendon and bone tissue are meant to move in alignment with the major force the body experiences: gravity, which pushes the weight of the body downward, and the opposite and equal ground reaction force the body experiences when the feet are on the ground. When tissue does not align with force, the likelihood of injury skyrockets.

“Stress.” is the body feeling that its likelihood of injury increases. Therefore, its defense mechanisms kick in. As a result, it does one of two things:

  1. It slows the body down in order to mitigate those forces to a comfortable level.
  2. It kicks up the stress response (and the heart rate), because it remains in a situation where there is a dangerous challenge to its physical integrity.

The increase in heart rate (and decrease in speed) is commensurate to the magnitude of the challenge.

Here’s the big lesson: if you want to reduce the body’s stress response to a particular task, increase its skill level.

Of course, there are myriad other stresses that conspire to wreck the body’s aerobic function: environmental, nutritional, even social. But the physical stress of poor alignment, due to the lack of skill required for the task, may be the larger part of the equation.

Running is an exceedingly complex task, biomechanically speaking, and it is performed by a full-fledged, multifaceted human, with imperfections and worries and commitments. Very few people have the privilege to be monks. Very few people have the privilege to increase their sleep, move far away from the chemicals endemic to the urban sphere, and detach themselves from the social preoccupations that come from being social animals.

But every one of us who has the time to run also has the time to perfect our running form. The problem is that few of us are aware that running form can be perfected, and that it is a way to reduce the stress of running. Misalignment is a real thing.

Alignment, or a lack of it, determines whether three astronauts get to return to Earth (or not). It determines whether our knees and hips survive the gauntlet of a hundred thousand steps we take during the marathon. It determines whether the body feels relaxed and competent when it analyzes its capability of performing a task.

“Aerobic training” isn’t the only way to approach the functionality of the aerobic system. Improving our form can do that too.

Athletic training: a game of physiological Jenga.

The 80-20 rule in athletic training* goes like this: train 80% of the time at a low intensity and 20% of the time at a high intensity, and you’ll achieve the best results.

Understandably, a lot of people—particularly us urbanites who are extremely busy and almost completely devoid of free time—might say: “but I only have a few hours to spare every week! I can’t afford to run slowly 80% of the time. How can I possibly expect to make gains?”

(Or something like that.)

This is exactly the wrong question. What running (a.k.a. training) at a low relative intensity—which people often refer to as “running slowly” does for the body is that it develops the aerobic system. (For most, but not all of us, training at a low relative intensity does indeed mean running slowly.) The aerobic system is extremely important: it mitigates oxidative stress (also known as chemical aging), it helps us recover from anaerobic efforts by processing lactate, and it keeps us well-fueled over the long-term by burning fats.

The aerobic system is the very foundation upon which any “gains” are built. In this sense, aerobic training increases what I like to call our “physiological capital,” that we can invest in high-intensity (anaerobic) training and develop what we typically refer to as “strength” and “power.”

To explain this relationship, I like to use the metaphor of a Jenga Tower.

Suppose that you have a particular strength or power goal: you want to run 6 minute miles. This is equivalent to wanting your Jenga tower to be 10 levels tall. But the problem is that you only have 20 bricks (each full level of a Jenga tower is 3 bricks).

The result is that you can only build 6 complete levels to your Jenga tower. You’re faced with a stark choice: you need to add levels to get to 10. But you don’t have any more bricks. So you’re forced to take from the lower levels. (This is essentially what strength training does). Your tower gets higher and higher—which is fine, until you pull out or lay a brick juust too quickly or a light breeze comes along—and the tower, which had grown increasingly unstable, plummets to the ground.

(You’ve just become injured.)

But there’s a way to add bricks to the base of your tower: aerobic training. This is what I mean by “increasing our physiological capital.” While aerobic training adds bricks at a pretty good rate, left to its own devices it turns your tower into a pyramid: the lowest level grows wider, until at some point  your body decides to start growing the next level.

That’s not a bad thing: a lot of ultrarunners (the healthy ones) have metabolisms that look like a shield volcano: gargantuan aerobic systems, but very little power. (If the height of the tower is how much power you possess, then the width of the base is how much distance you’re good for.)

Mauna_Kea_from_Mauna_Loa_Observatory,_Hawaii_-_20100913

That said, it’s not necessary to build a pyramid, when it’s a tower you want. Although it’s important that your tower be stable, that’s about it: most of us are not trying to be an ultrarunner, nor do we have to be. All you really need is a few extra bricks around your base—enough to plug any holes you may have created, and to be able to add a couple of levels. Rinse and repeat.

A quick disclaimer: the body doesn’t convert the actual aerobic machinery into anaerobic machinery in the way that a naïve reading of the “Jenga metaphor” would suggest: the brick that you take from the base is not literally the same one you put on top of the tower. However, the reason I like the Jenga metaphor is because the stress and wear-and-tear incurred by anaerobic work (compounded by the fact that it is the job of the aerobic system to absorb those stresses), means that the process of adding strength and power basically always means carving into your aerobic base.

How often do you switch from adding bricks to adding levels? If you’re looking to run an endurance race, for example, then you need a very wide aerobic base.

Supposing that you want to develop some all-around fitness, a basic (but certainly not universally applicable) recipe is this:

  1. For 2 weeks, train primarily easy 95-100% of your training.
  2. The next 2 weeks, train at a moderate-to-high intensity 35-40% of the time.
  3. Rinse and repeat.

This process will give your body two weeks to recover well from strength training (read: replenish the bricks you took from the base, and add a few more). Two weeks of low-intensity training isn’t really long enough to start losing high-end fitness: the small amount of strength training 0-5% during the easy weeks is more than enough to maintain your gains. But when you’ve cycled through this process several times is when you’ll really start to see your gains stack up.

Building and maintaining an aerobic base, and making sure that our strength gains are well-buttressed by wide lower levels of our metabolic tower, is non-negotiable. Some of us are lucky: for good or ill we spent our formative years playing at the beach, kicking around a soccer ball, or going hiking with our oudoorsy parents. This person (unbeknownst to them) has been stacking more and more bricks around the base their fledgling tower, broadening their aerobic base until they’ve accrued what seems like a limitless amount of bricks.

Others never had that chance.

But not having had that chance doesn’t mean we have any more of a choice. Sometimes, the unconscionable choice—running “slowly” despite the horrible feeling that time is slipping away and we’re not getting any faster (forgetting the fact that our pool of bricks is growing ever larger)—is also the right one. That choice will put us in a position from which we can develop speed . . . and get to keep it.


*NOT the Pareto Principle.

 

 

No good reasons to prioritize anaerobic training. At least 9 great reasons to do some.

A friend of mine recently asked for my thoughts on an article titled Nine reasons to prioritize anaerobic training over cardio. Leaving aside the issue that “cardio” is ill defined and often contains an anaerobic component (which means that it bugs me when people use the word), this is an extended version of what I answered.

My contention is that the article in question doesn’t actually give any good reasons to prioritize anaerobic training over “cardio”—by which I’m assuming the author means “aerobic training.” (For the rest of this article, I’m defining “aerobic training” in opposition to anaerobic training: “aerobic training” is training with no anaerobic component whatsoever).

Don’t get me wrong: the article gives 9 excellent reasons for why to include anaerobic training into your exercise routine. But I’m unconvinced that these are reasons for why to  prioritize anaerobic training in the sense of “if you only have time to do one of these two kinds of training, do anaerobic training.”

Simply stated, that’s not a good idea. While many may argue that I’m splitting hairs, consider what the effect of “why you should prioritize anaerobic training” is to a lay audience. (I believe that) the effect is “anaerobic training is better than aerobic training”. This raises an important question: if it’s good to prioritize anaerobic training, when exactly should we do aerobic training?

Although no training can be said to be “better than another” in a strictly metaphysical sense, aerobic training and anaerobic training each have their advantages. And it is when you consider their relative advantages over one another that the question I italicized above becomes so pertinent: the time to do aerobic training is in fact before and so that you can safely perform anaerobic training.

 So we return to the beginning: while anaerobic training is important and necessary and has its place, its place is auxiliary to aerobic training. This is why:

In my most popular article on the site, titled High-Intensity Fitness Culture, Explained in Systems, I discussed how the anaerobic system is essentially the emergency, high-intensity, powerful, dangerous, and rapidly-exhausting turbocharger that an organism uses to overcome an immediate threat to its existence.

While the anaerobic system is a critical system (worthy of development and training), there are costs to using it: anaerobic activity produces acidic hydrogen ions, which wear down the body. Those costs will become exacerbated insofar the anaerobic system becomes the dominant energy system in the body.

All of which brings us back to the aerobic system. What exactly, does the aerobic system do? Essentially, its function is to provide long-term energy to the body by oxidizing fats (combining fats with oxygen to provide energy), and to assist recovery from anaerobic activities by processing its main by-products: lactate and positive hydrogen ions.

Insofar as your anaerobic system is more powerful than your aerobic system, your body will have a more difficult time recovering from anaerobic workouts. This is a problem for those who gave given anaerobic training priority over aerobic training, and consequently possess anaerobic systems that are more powerful than their aerobic system can sustain.

The aerobic system also happens to be the system that the body uses for its upkeep and longevity. This is an issue for another article, but the reason is because “longevity” is essentially “long-term recovery”—in other words, the ability of the body to keep recovering for longer, before breaks down enough that it dies. (Here’s a hint you can use to reverse-engineer the content of my next article for yourself).

For the sake of clarity, let me reiterate what I discussed in paragraph 4: all the reasons given in the article I’m discussing are great reasons to do anaerobic training, all legitimate and grounded in extensive research. My contention is NOT that the reasons given in the article are somehow illegitimate, but rather that when they are cast as reasons to prioritize anaerobic training, they become (1) quite misleading to the lay audience and therefore (2) dangerous to those who take the article at its word(s)—the particular words in question being “prioritize over”—and naively follow them to their logical conclusion.

(I am NOT arguing that anaerobic training will become dangerous to those who take the words “prioritize over” to mean “modestly include” regular anaerobic workouts into their predominantly aerobic training).

QUESTION FROM A READER: Why does my heart rate spike at the start of a run?

A lot of people who run with heart rate monitors often see their heart rate spike at the beginning of a run, only to subside after a mile or two. This kind of spike only happens if you didn’t warm up long enough.

  • If the body isn’t warmed up, there is little blood flow to the muscles (and therefore little oxygen).
  • For a short period of time, the muscles have to work anaerobically, increasing the heart rate.
  • The body rushes to shunt blood away from the organs and towards the muscles. This is a major stressor.
  • The spike in heart rate subsides when increased blood flow (and the oxygen that comes with it) allows the muscles to work aerobically.
  • Therefore, the spike itself is an indicator that your heart rate was inadequate.
  • It takes 12-15 minutes for the body to warm up properly.

Before starting a bout of exercise, our body’s internal machinery is largely inactive. The metabolism is working at a very low level, the big muscles are relatively quiet, and blood is moving largely within the core—cycling through the various organs, and back to the heart and lungs.

Muscles are fed by vast networks of capillaries—tiny blood vessels existing within the muscles themselves—which ensure that blood goes to and from every muscle cell. During rest, the majority of these capillaries are constricted. Very little blood goes in or out of the muscles.

This eases the demand on the heart during rest: constriction of the capillaries and peripheral blood vessels means that the overall volume of the cardiovascular system is greatly reduced. The heart doesn’t need to pump very hard to maintain blood pressure, which keeps the heart rate relatively low.

During exercise, muscles demand a huge volume of blood flow, and so the capillaries dilate to accommodate it. But the body isn’t designed in such a way that the capillaries can expand pre-emptively. They expand due to exercise itself. Asking the body is asked to exert itself from a cold start can be a major stressor: it has to drain blood from major organs abruptly and it has to shove them into muscles whose capillaries haven’t dilated yet—a process that can send the body into shock.

Because of this, a proper warm-up—a period of very low-intensity activity—is important for all exercise, but is critical for running: Every step we run, our legs have to break our fall. It takes a big use of the muscles to make this happen.

Without proper blood flow, the muscles are on their own. If the capillary networks haven’t yet expanded, very little blood is getting to the muscles for those first few minutes. This is a problem because blood carries oxygen. No blood, no oxygen. But even without oxygen, the muscles still need to find a way to perform the required activity. In this situation, the only way to accomplish this is by working anaerobically.

I’ve written before how anaerobic work is intricately tied to the stress response: when the body is under stress, it raises the heart rate and kicks up the functioning of the anaerobic system—which is able to provide energy at a massive rate—in order to deal with a presumed threat to its existence. The connection between stress, anaerobic activity, and a high heart rate runs deep: if any of the 3 increases, the other two will follow.

The observed spike in heart rate is a direct indicator of increased anaerobic activity.

It subsides after a mile or two is because it typically takes the aerobic system 12-15 minutes to activate completely. Blood finally pervades the muscles, bringing oxygen and allowing the aerobic muscle fibers to do their thing.

Heart rate drops to a manageable level once the aerobic system is in play—and to the degree that it comes into play.

Here’s the important part: A spike in heart rate doesn’t just tell us that our aerobic system wasn’t fully on yet. It also tells us that our warm-up was inadequate. The spike in anaerobic activity means that blood and oxygen was largely absent from the muscles. The body was forced to rush to bring blood to the muscles. Blood was hastily drained from the organs, and unceremoniously shoved through capillaries that hadn’t yet expanded to accommodate it.

That amounts to a lot of unnecessary stress.

The solution: warm-up for longer.

Understanding the gears of the human drivetrain: energy systems and some of their training and racing applications.

Not long ago, I read an article from Outside Magazine which mentioned an elite cyclist who eschews heart rate monitoring during training in favor of power meters because “power is objective.” While I like power meters and I think they are an important tool in our (presumably much larger) athletic toolbox, I take issue with this view.

While a power meter tells us exactly how much power the body is putting out, it doesn’t tell us a lot about how the body is arranging for that power to be produced. That’s a problem.

The body has 2 main energy systems, both of which are used in varying amounts during a bout of activity: a capability to create energy by breaking down glucose, or sugar (call this “LO gear”—producing the low-end torque needed for power and acceleration) and a capability to create energy from lipids, or fat (call this “HI gear”—producing the high-end torque necessary for endurance). LO and HI gear can be subdivided into more energy systems—ATP-PC, anaerobic glycolysis, glucose oxidation, fat oxidation, and ketosis—but I believe that the beginner (particularly the beginner distance runner) should first master the distinction between fat and sugar usage, and how to apply it concretely to training and racing.

As I’ve discussed before, our heart rate is hardwired to our stress levels (a.k.a. the intensity at which our body is operating or expects to operate), and therefore to whether we are breaking down sugar or breaking down fats—in other words, which gear we are using at any given time.

The higher our heart rate, the more we are using the LO gear necessary to produce lots of power. The lower our heart rate, the more we are utilizing the HI gear necessary to sustain activity for protracted periods of time.

This doesn’t mean that we are burning the most fats when our heart rate is lowest—it just means that the greatest percentage of our energy comes from fats. By increasing our heart rate from its lowest point, we increase the amount of fats burned until the requirements of the task (as reflected by the heart rate) are high enough that a threshold is crossed—and the body is forced to switch to sugar in order to produce the necessary power.

(My favorite way of estimating at which point your body is most likely to switch from HI gear to LO gear is Phil Maffetone’s 180-Formula.)

Consequently, the problem with the power meter is that it doesn’t tell you whether the body is getting this energy from LO or from HI. The issue is simple—and it’s the very same one you would have if you’ve ever tried to go on a long roadtrip with a car that doesn’t shift up above second gear: you’re going to run out of fuel, blow the engine, or both.

During a marathon, just like during a road trip, your success depends on how well you’ve developed HI gear. Nobody argues that power (from LO gear) is incredibly important in a marathon—I often quote Owen Anderson, author of Running Science, who (in my opinion) famously said that “the marathon is a power race.” But the ability for you to get to the finish line (which is a precursor to racing to the finish line) is predicated on how well you developed HI gear.

“Hitting the wall” is a ubiquitous experience in the running community. I myself have hit the wall a dozen times. It’s almost a rite of passage—the badge of a “true” endurance athlete. It also means that muscle glycogen (a.k.a sugar) was depleted too soon: the runner was utilizing LO gear too much, and ate through all its fuel.

(HI gear—“fat-burning,” loosely speaking—draws from a massive fuel source. A 150 lb marathoner with 12% body fat has some 45,000 calories in the tank. LO gear has perhaps 2,000.)

Supposing that 60% of entrants at any given marathon are hitting the wall—although it wouldn’t surprise me if the real percentage was far higher—there is an epidemic of runners who despite their best intentions and best efforts, either (1) have not developed HI gear well enough, or (2) do not understand how to pace themselves in order to use just enough LO gear to go fast but not enough that they bonk at the halfway mark.

How do we factor this into training?

Let’s use the most classic bit of marathon training as an example: the long run. Since the marathon is a HI gear, fat-burning race, then we have to make sure that our long run is being fueled primarily by HI gear.

Suppose that some runner X has enough glycogen stores to fuel LO gear for 14 miles. If she’s been using LO gear to fuel the majority of her efforts up to the 14 mile mark, then she hasn’t really used HI gear to run even 1 mile.

This marathoner doesn’t really have a robust, well-developed HI gear to switch to. For her, a 14 mile run and a 16 mile run are extremely different experiences. The 14 mile run can be performed well with a powerful LO gear, but as soon as she bumps the distance up to 16 miles or more, her speed will drop dramatically—particularly towards the later miles.

(Marathon pace for the elite runner is only a few seconds per mile slower than half-marathon pace. In contrast, marathon pace for the recreational runner may be a third slower than half-marathon pace).

The problem isn’t that she hasn’t trained the mileage itself, but rather that the energy system that is supposed to handle high volumes of mileage was never really developed—so when she bumps up to a mileage that requires that fat-burning energy system, she grossly underperforms relative to her expectations.

Considering how many marathoners hit the wall, I believe that most of us don’t train HI gear on most of our long runs. This doesn’t mean we shouldn’t train LO gear or run long and fast in preparation for a marathon. It means that we need a reason for doing so—and we need to know when we’re crossing the threshold. Power meters aren’t enough. We need heart rate monitors: we need a window into what’s happening inside our body in real time.

Running MAF

NOTE: This is an unusually journal-entry-ish post for me. But I think it has some pretty useful concepts. I hope you like it. (Any mention of today refers to Friday, Sept 18, 2015).

For about 2 months now, I’ve been building my aerobic base under the MAF (Maximum Aerobic Function) principle, proposed by Phil Maffetone. I’ve seen an improvement of about 1 minute to my MAF pace—the speed at my aerobic heart rate, which is 148—and yet, I feel like today is the first day I really understood what running MAF is like.

The idea behind MAF training is to lower the intensity at which we train, in order for the aerobic base to kick in with theoretically no anaerobic function. This removes the majority of chemical stress associated which exercise, which comes from the release of hydrogen ions (H+). These ions acidify the body and create an added burden for recovery.

Training under this “aerobic threshold” allows the aerobic base to be developed quickly and efficiently. Typically, 3 to 6 month long period of exclusive MAF training strengthens the aerobic base to the point where it can efficiently absorb the stresses of high-intensity (anaerobic) exercise.

As editor on the MAF website, I answer a lot of difficult questions in the comment sections. For people are first calculating their MAF heart rate, a predictable question always pops up:

“Are you sure that my MAF Heart Rate is 148?” (or whatever). “This can’t be! I’m, like, really athletic. I stuck my first vault at 4 months of age. At two, I was running 5 minute miles. Are you sure it’s not at least 151?”

And honestly, I often feel exactly that way. It’s as if everyone (myself included) is trying to negotiate their way into a higher heart rate—thinking it is the highest possible heart rate (aerobic or otherwise) that will bring the most benefit.

I constantly tell commenters what it has taken until now for me to truly absorb: we have to lower the intensity to maximize the aerobic benefit. Trying to always be right on top of that aerobic threshold—what I’ve decided to call greenlining (as a riff on “redlining”)—is that very same high-intensity mentality, haunting a game that’s all about going low, not high.

Don’t get me wrong: when I run MAF—usually 1 hour, 5 days a week—I scrupulously bookend my workout with 15 minutes of warm-up and cool-down, in which I slowly and steadily bring my heart rate 3 or 4 BPM under my aerobic threshold.

Every warm-up, I notice the same thing: my heart rate oscillates its way up to MAF. It doesn’t climb steadily. Even once I do get close to MAF, it keeps oscillating. It goes up and down some 4 heart beats every 30 seconds or so, meaning that if I want to stay under MAF (which for me is 148) I have to stick with 143.

As a perfectionist, I always try to iron these things out. Maybe it’s fine for the heart rate to oscillate as long as it remains under MAF. But it’s still important to consider what oscillations mean. It means that metabolic work (and my speed) is rising and falling continually, when in theory we want to stay at the same metabolic output.

Maybe I’m overthinking this far and away, but to me this seems like a car lurching down the highway when a few tweaks to the engine would be all that’s needed to create a smoother ride.

Almost by accident, that is exactly what i did. It had been an uncharacteristically bad run: I went out after an hour of having eaten, and I just didn’t want to take my heart rate up there. I did my warm-up, and then dropped back down to 20 under MAF. I just felt like jogging.

As the minutes passed, my heart rate—and my speed—slowly began to increase, at a rate of about one beat per minute. And like that, over the next 20 minutes, I slowly approached MAF. My heart rate came to within 1 BPM, and for the next 40-45 minutes, held constant.

Today’s run was exceptional: I had far better joint stacking. It was extremely easy to keep my breathing in sync with my steps—three steps to an exhale and two to an inhale—and my breathing was also deeper than usual. The experience of running was one of incredibly little stress. When I did get up to MAF speed, I was faster by a full 15 seconds per mile.

And two hours after the run, I was full of energy, and my leg muscles, instead of feeling empty, felt warm and fuzzy. I’m not kidding.

But this makes perfect sense to me: calibration, not raw power, is the primary source of performance. Think of a 1000-horsepower engine with a timing belt that’s just a tiny bit loose. It can’t express a bit of that power. Think of that same engine attached to a gear box with all the wrong ratios, or mounted on a car whose tires are too pressurized. When that engine expresses all of its power, that car is going sideways.

Too often, as athletes and fitness enthusiasts we try to add horsepower when we should be checking the timing belt, or changing the stiffness of our valve springs. I think that in today’s workout—which feels like the highest-quality workout of my life—I enabled my body to focus on the small stuff . . . and get it right.

I’m willing to bet that this very long, very easy warm-up, which “sacrificed” time spent training at a higher intensity, was a central part of it. And I expect my bet to pay dividends in speed.

UPDATE: On Saturday I had an even more protracted warm-up. My speed increased by yet another 20 sec/mile.

The Maffetone Method, training the aerobic system, and answers to common frustrations.

For the past few months, I’ve been working in various capacities with Phil Maffetone, who has made many important contributions to exercise science and the endurance sports. He is a proponent that aerobic function—the ability of the aerobic system to utilize fat and oxygen to power the body—is the foundation for all health and athletic achievement.

In a recent article, I discussed this view from an evolutionary perspective: the aerobic system is in charge of the long-term upkeep of the body. Conversely, the functioning of the anaerobic system (which burns sugar in the absence of oxygen) is tied to the autonomic stress response, and necessarily coincides with a high heart rate. The organism primarily uses the anaerobic system to survive an imminent threat to its existence, or (in the case of predators) to capitalize on an opportunity for its survival.

When the anaerobic system stays on for too long—or becomes responsible for the body’s upkeep—chaos ensues. The Maffetone Method (also known as MAF) is all about bringing order to this chaos, and therefore facilitating the body to develop correctly.

A majority of people who try out Phil’s recommendations for the first time—(train at a heart rate that guarantees aerobic function while excluding all anaerobic function)—find that this means running very, very slow. And furthermore, a number of people don’t observe changes to their “aerobic fitness” for some time.

The problem isn’t that the method “doesn’t work.” It’s just that some of our bodies (and in particular, our aerobic engines) are in a state of utter disrepair—and the body is an extremely smart investor. The body will sometimes use the fledgling aerobic system to patch itself up and fill in the cracks before using its newfound potential for anything else.

I often hear that the aerobic system develops slowly. I believe that it develops astonishingly quickly. But while our attention is on the “fitness” we so desperately want—which we want so much that we rarely bother to define it—we miss the fact that the aerobic system is diligently working to achieve it.

Often, the body’s last priority is increasing athletic ability—as it should be. Think about it: if we are succumbing to infections because our aerobic system is struggling to power our immune response, or our bones have insufficient density due to increased acidity (which the aerobic system potently counteracts), then the last thing that we want is to be subjecting this engine to more stress.

This is car engine whose piston rings are rotten. Its valve springs are rusting off and its fuel injection system is all clogged up. Not only do we have no business racing this engine, but the very last thing we should do to it is add a turbocharger. That’s not what this engine needs. But the systems of the human body are so opaque to us, and the cultural narratives around athleticism so damaging, that this is exactly the position that we find ourselves maneuvered into—and outright believing.

ferrari
The human aerobic engine comes from an even better brand. But we need to look under the hood to notice.

Before the body is ready to be challenged with anaerobic exertion, the aerobic system must have achieved 3 benchmarks of competence: (1) as mentioned above, it must provide the overwhelming majority of the energy for the body’s basic upkeep, (2) it must be powerful enough to sustain a high level of brain function—while the muscles are hybrid engines, the brain is exclusively an aerobic animal—and (3) it must be able to adequately absorb the stresses incurred from present lifestyle.

When an underdeveloped aerobic system is being trained, any gains that are made will go towards securing the body’s basic upkeep: if there were chronic issues—such as carbohydrate intolerance, infections, etc—all gains will go first to combat those, and to make sure that they do not reappear. Speed will not increase.

Once that step is complete, any gains in aerobic function will go towards maintaining a high level of stable cognitive function throughout the day: if you had low or fluctuating energy levels, any gains will go towards stabilizing those. Speed will not increase.

And there’s the issue of present anaerobic function: if your your lifestyle or work demands a heightened level of focus, (or hell, you run two blocks with a backpack to catch the bus every day), your aerobic system will have to be that much more robust before it will be able to start contributing anything to your athletic output. Speed will not increase.

Phil Maffetone’s approach to health and athletic achievement does not just require us to develop the aerobic system. When discussing why our aerobic system is so underdeveloped, the Maffetone Method helps us realize that the present fitness culture (and the assumptions and beliefs that surround it) need a major overhaul.

Two people—one with a hugely powerful aerobic system and one without—will find that they have a very different “training response.” One will be able to tolerate a magnificent training volume, and one won’t. Present exercise science—and our own fitness instructors—will often tell us that the issue is genetic, or that we’re not good athletes. But a lot of times, that simply isn’t the case.