Tag Archives: Running

In defense of the endurance running hypothesis, part 1: how we think about evolution.

The endurance running hypothesis is the idea that humans evolved primarily as endurance runners. The argument goes that the human physique evolved and took its shape and function from the primary adaptive pressure of persistence huntingthat of chasing down our prey until its body shuts down.

However, this hypothesis is not without its detractors. A significant amount of scientists provide an array of counterevidence to the endurance running hypothesis. (And the debate continues.)

Take for example the case of the human gluteus maximus (butt muscle). Lieberman et. al. (2006) claim that the human gluteus maximus evolved its shape and size due to endurance running.

However, another article in the Journal of Comparative Human Biology finds that the gluteus maximus grows much more in high-force sports (weightlifting) and high-impact sports (such as soccer), than it does in endurance running. In fact, they also show that the butt muscle in endurance runners is no larger than in the non-athlete population.

What I disagree with is their conclusion, which is paraphrased in the “What does this mean?” section in the image below:

“The human gluteus maximus likely did NOT evolve through endurance running, but through varied explosive and forceful activities.”


My disagreements with the article (and the image) are primarily about how and why we interpret the science to mean a certain thing.

At first blush, the fact that endurance running doesn’t enlarge the gluteus maximus as much as other sports seems to detract from the idea that the muscle takes its shape from endurance running. But I think it actually adds to it.

By my analysis, these findings show that the basic, untrained shape and size of the gluteus maximus—it’s “factory specifications,” if you will—assume that it’s going to do the amounts of cutting, jumping, weightlifting, and sprinting that a habitual endurance runner might need to do. But it requires aftermarket modification to meet the (literally) outsize power and stability requirements of soccer or weightlifting.

Let’s say that a muscle evolved under a particular adaptive pressure. This means that its shape and size literally evolved to do that thing. If you take a muscle that usually doesn’t do a thing for which it evolved to do, and you ask it to do that thing, you are asking it to do something that it has prepared to do for millions of years of evolution.

In order to fit a function that it has been designed to do, the changes in shape and size that the muscle should have to undergo should be smaller, not larger. You would expect a muscle to change far more if you ask it to do something that is less aligned with its evolutionary job description.

Let’s illustrate this by looking at the arm and hand.

We probably all agree that one of the things that specifically sets us apart from our hominid cousins is the ability to coordinate the thumb with the rest of the fingers in order to grasp and manipulate objects to a high degree of dexterity. In its simplest form, this is the capability to oppose the thumb and the fingers—to make an “OK” sign with the thumb and each of the fingers of each hand.

Now let’s take a snapshot of the people who take this unique human ability to its very pinnacle: string musicians, graphic artists, etc. Their livelihood depends on the degree to which they can explore the potential of one of the major evolutionary functions of the human hand.

Compare the forearm muscles of a violinist or painter with that of a weightlifter. The weightlifter’s arms, hands, and shoulders will be much larger and more powerful. (I trust I need not cite a scientific, randomly-controlled study on the matter.) Why? Quite simple: weightlifters engage in activities that develop the body to phenomenal proportions.

But if we go by the conclusions of the article, the fact that the arm and hand get bigger through weightlifting would mean that it didn’t evolve for the kind of fine motor control that you produce in the arts. (Or that lifting heavy objects is its primary evolutionary role). A particularly ambitious version of this argument would be to suggest that one of the core functions of opposition is to become better able to lift heavy objects. But all these suppositions break down when you realize that our primate cousins were not only quite able to grasp branches and use them ably, but that opposition emerges at the same time that hominid arms were becoming smaller (and less powerful), not larger (and more powerful).

Of course, the human hand (and upper extremity in general) still needs to be able to grow and develop in order to be able to lift heavy objects—and can indeed grow to a huge degree to exhibit that function. But its core evolutionary function is to produce the unparalleled dexterity of the human being.

Furthermore, the fact that the non-painter’s hand remains relatively unchanged in size compared to the painter’s hand means that the non-painter’s hand is already relatively set up to perform that kind of dextrous function—because that’s what it presumably evolved to do. This should serve as evidence (not counterevidence) that the hand is primarily for painting (and other fine motor tasks), not for weightlifting.

We should think the same of the gluteus maximus.

Let me conclude by saying that nothing I’ve written here means that the gluteus maximus evolved exclusively for endurance running. Indeed, there is ample evidence suggesting that the architecture of the gluteus maximus is uniquely multifunction as far as muscles go. (In future posts, I’ll delve more into the nuanced view of the gluteus maximus that I proposed above: that it owes its shape and size to the fact that it is a muscle designed for the kinds of “varied explosive and forceful activities” that a bipedal, primarily endurance running animal expects to have to do.)

But what we can say is that the fact that the gluteus maximus gets bigger through a particular stimulus has no bearing on its core evolutionary role, (or on the evolutionary story of the organism as a whole).

Marathon Training, Part 1: Basic Requirements

When people want to know how to train for a marathon, they usually ask you for a training plan. This typically typically center around the following:

  • What kinds of workouts you’re supposed do.
  • How long those workouts should be.
  • How long you have to train before you’re ready.

Answering these questions is very difficult (if not impossible). Everyone is different, and begins their training at a different point. 

These questions are far too vague (or depending how you look at it, far too specific). It’s only a question that applies to you in particular. So instead of providing a training plan, I like to arrive at the issue from a different direction. The question I ask is:

How do you know that a body is ready for a marathon?

This question is much more useful. Why? Because being ready for a marathon is the same for every human.

The catch is that how to get there might be wildly different from one person to the next. For one particular person, your basic marathon training plan might be exactly what they need. Someone else may need to train for much longer, or with less intensity (or both). For yet another person, it might not include a crucial element that particular person needs—an element with which the training plan might work perfectly.

You’ll find that when you genuinely ask the above question—and truly inquire as to what it takes for a body to be physically and physiologically ready to run a marathon—you’ll inevitably conclude that ninety-five percent of the people who do cross the finish line of a marathon were not prepared to run the race.

I believe that one of the most important reasons that injury and illness is so rampant in the marathon is NOT because the marathon is inherently injurious, but rather because it is so physically and physiologically demandingand the vast majority of people who run it have not achieved the capability of meeting those demands.

A major goal of mine in life is that people do NOT get injured running a marathon (or any other race). And I believe that a first step in that direction is to help people understand what “being ready for a marathon” really means from a physical and physiological standpoint—beginning with the idea that there is such a thing as being “marathon-ready.” Only then can we genuinely expect ourselves—the individuals who constitute a modern athletic culture—to face a marathon with every expectation of success.

 I answer the question of marathon readiness in the following ways:


In order to run at peak efficiency, you must be able to sustain a cadence in the ballpark of 180 steps per minute (spm). This is important because the critical systems necessary for maximizing running economy only become activated at around that cadence. For an array of biomechanic and metabolic reasons, it’s important that our definition of “running” includes the activation of these critical systems. The above means that to run a marathon:


It is said that 99% of the energy that you use to run a marathon comes from the aerobic system. This means that you must be able to run the race at an overwhelmingly aerobic intensity. How fast?

Putting the two together

The above two requirements, when put together, give us a third, “master” requirement:

  • You must be able to produce a cadence in the ballpark of 180 spm while running at a pace that is 15 sec/mile faster than your speed at aerobic threshold, and maintain it for the duration of the marathon.

A word on training load

There’s another way to look at this issue: how much someone needs to be able to sustainably train in a given week to be reasonably certain that they can run the race.

Sustainably means that there is no increase in stress, no nagging pains, and every reason to believe that the body can continue to train at that rate without injury.

So, a marathoner’s easy week should look like:

  • A volume of twice the race distance (50-53 miles).
  • An intensity that is exclusively aerobic (under the aerobic threshold).

*A good way to estimate the aerobic threshold without the need for a laboratory is by using Dr. Phil Maffetone’s 180-Formula. The 180-Formula produces the MAF HR, or Maximum Aerobic Function Heart Rate.

Sample easy week

All training is under the MAF HR, and cadence remains relatively close to 180 spm.

  • Mon    7 mi
  • Tue     9 mi
  • Wed    7 mi
  • Thu     9 mi
  • Fri       7 mi
  • Sat       12 mi
  • Sun     REST


There are no guarantees in life. But if you can run an easy week like this, I can be reasonably sure that you’re ready (or almost ready) to run a marathon. How to work up to this, and how to navigate the many pitfalls and angles of the journey, is the hard part.

Part of why I rarely give training plans or talk about these requirements—popular demand has essentially forced me to—is because you can’t really meet them if you haven’t ironed out all of the physiological, biomechanic, and neuromuscular issues your body may have.

(And again: that’s the hard part—and it’s the part that you can’t really address with a training plan.)

And even if the prospect of running a marathon has never been in your sights, once you do iron out enough of your body’s athletic issues, you’ll find that going on 25-odd mile, easy long runs every month has become a fact of life. You’ve become familiar with the distance—and the idea of running it a little faster with a lot of other people seems as simple as that.

(This post is about being ready for a marathon. How to become competitive at the marathon is, of course, a different question.)

Runners: “Aerobic training” is not the same as “Endurance training.”

It’s common that training which develops the aerobic system is equated with training that increases the body’s endurance. It’s understandable: the aerobic system burns fats in the presence of oxygen in order to provide long-term energy for the body—exactly what it needs for endurance. But the problem is that a powerful aerobic system isn’t the only thing necessary for increase endurance.

The most important difference between “aerobic training” and “endurance training” is this: the former trains a critical supersystem of the human body (the aerobic system), while the latter improves the product of the successful interaction between the aerobic system and many other parts and functions of the body (endurance performance).

What runs isn’t the aerobic system—it’s the entire body. While the aerobic system can be powerful, it can’t perform on its own. Whenever we talk about “performance,” even when the subject is endurance performance, we’re talking about how (and how well) the body uses its aerobic power to create one particular kind of athletic movement.

Roughly, endurance means: “how long the body can produce a particular movement or action without falling below a minimum threshold of performance.”

Another way to say this is that the aerobic power is general, and endurance is specific. Geoffrey Mutai (elite marathoner) and Alberto Contador (Tour de France cyclist) both have extraordinary aerobic systems. In both athletes, all the parts that enable their muscles to be fueled for long periods of time are extremely developed.

It should be noted that in both athletes, we are talking about developing essentially the same parts, developed to comparable levels and talking to each other in very similar ways. Both these athletes also obtain fundamentally the same general physiological benefits—a greater ability to recover, better health, longer careers—all despite competing in wildly different sports.

However, their endurance in specific sports varies wildly. We can expect Mutai to be a proficient cyclist, and Contador to be an able runner, but we can expect neither to have world-class endurance in the other’s field. In other words, Mutai’s endurance is specific to running, and Contador’s is specific to cycling. This is because:

  • Both sports use different sets of muscles: runners use a larger set of muscles for stability than cyclists, since the latter have so many more points of support. Cyclists have the handlebars, pedals, and seat, whereas runners have at most 1 foot on the ground.
  • They load joints in different ways, and use very different ranges of motion: cyclists keep their waist and hips relatively flexed, while runners keep the same joints extended.
  • They use different neuromuscular mechanisms to facilitate endurance: running economy depends on a powerful stretch-shortening cycle, while cycling economy does not.

In my opinion, the stretch-shortening cycle is the most important piece of the running puzzle (and also one of the most overlooked). Running shares a lot of pieces with just about every sport—and developing them is very important if you want to become a good runner. But without an increasingly powerful stretch-shortening cycle, all the power that you develop in any other system (cardiovascular, respiratory, etc.) doesn’t translate into actual running performance increases.

As discussed above, the aerobic system is responsible for sustaining endurance. The best way to exclusively train the aerobic system is by running at a physiologically intensity (below the aerobic threshold).

This is a problem for less aerobically-developed runners: it takes a lot of juice to run the stretch-shortening cycle effectively. In previous posts I discussed how the minimum requirement for running properly is to be able to produce a (very fast) cadence of around 180 steps per minute (spm). This is because the muscles’ stretch-shortening cycle hits peak efficiency around that cadence.

So, these runners often need to run at a higher intensity: they’ll use the maximum output of the aerobic system at max and engage some of the anaerobic system in order to produce a cadence of 180 and properly activate their stretch-shortening cycle. If they fall below their aerobic threshold with the goal of doing “aerobic training,” their cadence falls and the stretch-shortening cycle will largely deactivate.

When I talk about hitting 180, I mean hitting 180 at an average step length: It’s possible for a weaker runner to shorten their stride to artificially increase their cadence without going above the aerobic threshold. But I consider this a rather useless hack, since in my experience it doesn’t really get runners the performance benefits expected of reaching “the magic 180 mark.” (More on this in a future post.)

For a workout to be “running performance training” (endurance or otherwise), it needs to train the key pieces necessary to improve running performance. So whenever you’re not actively training the stretch-shortening cycle, you’re not really doing “running performance training” in my book. “Running endurance training” would be about teaching the body how to run for longer, at a lower intensity, while maintaining a reasonable cadence.

So, whenever an aerobically weak runner trains under the aerobic threshold, I consider it to be quality aerobic training but NOT “running performance training.”

It’s not that their running performance won’t increase—it will. Let me illustrate with a rather extreme example: If playing checkers is the only active thing someone does, playing checkers is better for their running performance than not doing so. But because it doesn’t train the critical systems for running, I don’t think of it as “running performance training.”

Of course, running at a low cadence shares a lot more with running at a high cadence than playing checkers does. But the idea here is to set the highest possible bar for what “running performance training” should mean: training the key systems that running performance rests on. And running without substantially activating the stretch-shortening cycle really doesn’t meet that criteria.

(We can say that running without the stretch-shortening cycle still helps you to improve your running—to a point. But you can’t hope to maximize your performance gains without it.)

For a competent runner (someone who can engage their stretch-shortening cycle at low physiological intensity), “aerobic training” and “running endurance training” become identical: just about all of their training provides all the benefits they need to maximize their running endurance.

What is a less-powerful runner to do with all this information? If I could say only one thing:

Jump rope! Jumping rope (on both feet, alternating feet, on one foot, spinning around, crossing the rope, etc.) is training primarily the stretch-shortening cycle up and down the body, almost identically to the way it’s used in running. IMO, if a runner does only one other thing besides running, it should be to explore and master the jump rope to its fullest potential.

UPDATE Nov 18, 2016: Another (great!) article on the mechanics of running, also touting the potential of jumping rope.

But there’s a lot more than this. Now that I’ve covered all the theoretical ground I absolutely need to cover for my following posts to have any real substance, I can begin to discuss concrete strategies that the runner can use.

Addendum (for the curious): Why do I focus so much on fleshing out the principles (and, more importantly, taking so long to get to the processes)?

Because the idea, of course, isn’t to “balance” aerobic training with performance training. (That’ll only increase endurance.) The idea is to potentiate aerobic training with performance training. (That’ll maximize endurance.) And to turn balance into potentiation, it’s necessary to already have understood the “why.”

The Runner’s Catch-22, Part 1

I’m calling this series of posts “The Runner’s Catch-22” to address a very common problem in the running world. A lot of beginner runners—let’s face it—want to run long. Very long. But in attempting to do that, they get ill, injured, or overtrained. And their hopes of running long (and doing so consistently) get quashed.

Running isn’t just about running (as every injured runner knows). It’s about how to run well. But in all sports—in fact, in all movement—there’s a minimum power requirement that must be met: if you want to stand (correctly), your legs, along with your core and spine, have to be able to move into a standing position and be strong enough to support you. If you want to walk (well), your leg joints have to be able to flex and extend to a certain degree, and one leg has to be able to support more than your bodyweight while the other travels through the air. And if you want to run (properly) you have to be able to meet an even more demanding set of requirements. And this is where the story of the “Runner’s Catch-22” really begins.

A lot of things have to be working well for a runner to be powerful—form and movement are vital, for example. Having proper form feeds into your ability to produce power (in the same way that it would work for a weightlifter or a baseball player). So with poor form, you might never be able to meet the power requirement—or go significantly beyond it. So, what is this power requirement?

The body must be able to produce a habitual cadence in the ballpark of 180 steps per minute (spm). 

The body is most efficient at around 180 spm: this is the cadence that best engages the tendons’ elastic component, maximizing the amount of energy that can be taken from the previous step put into the next one. (This is a concept also known as energy return).

UPDATE: For people who are new to running (particularly those who only started being active as adults), meeting that power requirement usually requires a lot of power training, which is a problem for beginners. Experienced runners often are able to produce a cadence of 180 spm easily and habitually, for runs of any distance. (In fact, hitting 180 easily is how I would define “experienced.”) If that’s you, most of this post won’t apply to you.

Power training uses and develops the body’s anaerobic system, which is very powerful, but also produces negative by-products that, in large quantities, are ruinous to the body’s tissues. The anaerobic system is counterbalanced by the aerobic system, which disposes of those harmful by-products and allows the body to remain in activity for long periods of time.

So if you want to be able to train without trashing your body, you need a powerful aerobic system to support the anaerobic system. Just one little problem: while the anaerobic (powerful but dirty) system grows extremely quickly, the aerobic (less powerful but clean) system grows veeery sloooowly.

This is the runner’s Catch-22: Until you have a well-trained aerobic system, it is almost impossible to safely do large amounts of anaerobic training. Trying usually means burnout, illness, injury, or overtraining. But if you can’t do a lot of anaerobic training, you can’t develop power to the point that you can produce an efficient cadence (of 180 spm) at the kinds of low intensities where you can develop the aerobic system.

The wrong move—the one that so many runners take—is to lower their cadence to run more distance. Why? Because they’re set on running, or because they don’t know that there’s better ways to train the aerobic system when you’re not powerful enough to ballpark 180 spm:

  • Cycling/Spinning
  • Walking
  • Rowing

(I’d add bodyweight circuit training to this list, but it’s typically far more aerobically demanding than running would be.)

It’s important to realize that the other option—running at an inefficient cadence while the aerobic system develops—is NOT a neutral, “eh, screw it,” kind of option. It’s not very bad—the aerobic system will probably still develop in time—but it’s not the fastest way to train, and certainly not the best way to guarantee you’ll achieve your goal.

(There’s ways to produce a cadence of 180 at slower speeds, such as shortening your stride. But that opens another can of worms—to be featured in another post of this series.)

Learning a movement pattern the wrong-slash-less powerful way—yes, they really are the same thing—is the best (and probably least-discussed) way to prevent you from performing at a high level. If you learn how to throw a ball by releasing it far forward of your body instead of at ear level, you’ll very quickly plateau in terms of how much force you are able to put into it (meaning that you’ll never throw at 60 mph, let alone 90).

Your body develops through movement. If you don’t move, you don’t use your muscles, which means that your metabolism doesn’t develop.  If you can’t throw a ball faster than 60 mph (because of poor mechanics), your muscles won’t be able to grow in strength beyond what it takes to throw the ball at 60 mph. So your metabolism (aerobic or anaerobic) will never need to grow beyond that.

It’s impossible for your metabolism to grow to be able to produce an energy expenditure that you don’t have the biomechanic possibilities to harness.

Slow or low-cadence running isn’t a death sentence. Slow runners with relatively few biomechanical problems or muscle imbalances do increase their cadence and low-level strength by slow running . . . in time. So it’s often the case that people do end up running much faster and at a much higher cadence after a few months (or years) of slow running. But your power (and your cadence) won’t improve with slow running as fast as it could with actual power and cadence training.

How to get around the Catch-22? Below is the short answer. (The long answer will take a few posts).

  • An overwhelming amount of aerobic training (in sports where you can meet the power requirement).
  • A small amount of running-specific power training (mostly plyometrics).
  • A small amount of running at a cadence in the ballpark of 180 spm.
  • Monitor metrics including HRV (heart rate variability) and MAF (Maximum Aerobic Function) Test to determine your short- and long-term physiological readiness for power training.

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.

Synthetic perspectives on the running human body: Improving running economy is not the be-all, end-all.

Looking at the body from a synthetic perspective is a lot like looking at it from an evolutionary perspective.

As I described in a previous post, a “synthetic account” of the body—there is no such thing as a “synthetic analysis”—is one that looks at the human animal in its whole context in order to understand why it does what it does, (and what it is attempting to do).

A few theories have a strong synthetic component: Pose Method (which looks at the mechanics of the body in the context of the Earth’s gravitational field), Tim Noakes’ Central Governor Theory as well as his discussion on thirst and hydration, and Phil Maffetone’s MAF Method (which observes that prolonged athletic achievement cannot be produced without safeguarding and promoting the body’s health).

But most accounts of athletic performance out there look at the human body in a very narrow analytic sense. They typically only measure a few variables germane to athletic performance: running economy (also known as efficiency), speed, power, endurance, etc. In other words, they look at the body in the same way you might look at a race car: you analyze how the race car functions and how it performs while on the track. But you don’t worry very much about what it’s doing or what’s happening to it elsewhere.

In this vein, it is often argued that one running form (one particular set of kinematics) is better or more advantageous than another on the grounds that it is more efficient. Take a look at the title of these articles: A Novel Running Mechanic’s Class Changes Kinematics but not Running Economyand Effect of a global alteration of running technique on kinematics and economy. 

The body has to worry about a number of things beyond running economy: it has to save itself for future battles, quickly rest and recover in order to fulfill any number of foreseen and unforeseen functions beyond the scope of the athletic event, like for example to be unstressed enough to be able to engage smoothly and creatively with social environments.

So, when sports scientists come along and suggest that the best form for a particular athletic movement is what’s most efficient (in the sense of minimizing energy expenditure during the athletic event), they are ignoring some of the body’s broader imperatives.

Why? The simple answer is that the body’s lifelong goal of protecting itself is far more important to it than the very bounded goal of winning some particular athletic event (or chasing down some particular deer) at any cost. It doesn’t just want to get the deer. It wants to benefit from having gotten it.

What does this mean? That benefiting from getting a deer means that it might be better to wait until a slower deer comes by. Let’s suppose you don’t have enough energy to run at the speed and distance you’ll need if you want to catch the deer you want, and still be able to run with the form necessary to protect your body while doing so. You might end up catching the deer, but you might also end up with a blown knee or a damaged achilles. You might be put out of commission for a month or two.

Now let’s suppose that someone else uses a slightly more expensive form—expending more energy to maintain proper movement. They’ll be proportionally slower, but they’ll also be able to move much more and recover much faster. Over time, they’ll become the more powerful runners. Three or four years down the line, they’ll be catching much faster deer, much more consistently.

Of course, it’s important to be as efficient as possible: refining the way muscles work, and aligning them to work with gravity and impact forces (and not against them). But pursuing efficiency is not at all convenient past the point where the only way to get more efficient is to risk tearing tendons, degrading cartilage and connective tissue, and abrading bone.

This brings up another important point: while the safest form has a high degree of efficiency, the checks and balances necessary to produce it (and maintain it at high speeds or over many miles) also means that it is typically more expensive to produce than the “most efficient” form.

 Let’s say that the runner who blew his knee by going after the very fast deer has form X. Form Y might be more expensive, but it would also allow him to get faster over time. But let’s say that instead of getting injured by going faster, he decides to only chase the slowest deer, or run exclusively for fun. He might display the same injury rates as runner Y. But if we only look at injury rates without looking at speed, or running economy without looking at speed, or efficiency without looking at performance improvement over time, we might end up concluding that the wrong ways of doing things are actually better (or worse, that there is no “best” way of doing something).

Being faster (or fast for longer) is great. But that’s not good enough either. The same things that we said about efficiency can also be said about speed. Running with the form that lets you be fast safely, recover quickly, and improve consistently, is waaay better than “just running fast.”

The role of downforce in forward motion.

There are two main camps in the argument of exactly how we manage to move forward as we run. The traditional camp says that the body uses the muscles to “push against the ground.” The other—constituted almost solely by Dr. Nicholas Romanov’s Pose Method—proposes that we move forward thanks to the action of gravity on our bodies.

This second camp suggests that what the muscles do—their primary function—is to convert the downward force of gravity into net forward movement.

But how is it possible that the body can convert a downward force into horizontal movement?

Part of the answer lies in the fact that the running movement isn’t really horizontal. It consists of a wave-like movement of the hips and torso—an oscillation—that only seems to be a straight line if we’ve zoomed out far enough. If your model (incorrectly) assumes that the body is trying to convert a downward force into a force that travels on a horizontal linear vector, you’ll end up quite confused.

(But that’s a discussion for a different post.)

Let’s get to the issue I want to talk about: Proponents of the idea that runners “push off” often understand Dr. Romanov’s argument—that gravity is the “driving force”—as claiming that gravity provides “free” or “additional” energy (a.k.a. net energy) if we adopt a certain technique.

I believe that’s a rather shallow misrepresentation of what Dr. Romanov’s Pose Method has  actually suggested. Pose’s main message regarding the action of gravity in running is quite a bit more profound. To explain why this is—and what I believe the main message of Pose is—let’s abstract away from mentions of “gravity” for a second and talk about a more general concept: downforce.

Instead of runners, let’s look at race cars. What are the necessary factors in making them go?

First and foremost, a race car needs a powerful engine. Without an engine, it’s going nowhere. But an engine is not enough. As any connoisseur of modern racing will tell you, there came a point in the evolution of car racing in which the engine’s ability to turn the wheels exceeded the ability of the best tires to grip the best track.

Why? Engine power eventually exceeded the car’s weight (defined as “how much force is generated as gravity accelerates its mass towards the ground”), and the capacity of the tires and the track to covert that weight into friction.

This reveals an important truth about the car: the engine actually isn’t for moving the car forward. The function of the engine is to spin the wheels. (While this results in driving the car forward, actual forward motion only occurs insofar as the power with which the engine spins the wheels coincides with the extent to which gravity keeps the car on the track.)

At this point, the only way to achieve greater speed was for engineers to somehow find a way to add to the downward force that gravity exerts on the car. How did they solve this dilemma? By adding the ugly inverted wings we now see on the back of every Formula 1 and drag racer: spoilers.

By redirecting the flow of air upwards at the tail end of the car, spoilers create another significant downforce. This reveals that strictly speaking, it isn’t gravity that allows race cars to move forward. It’s downforce. (Gravity just happens to be the quintessential downforce on Earth.)  But the point is this: no downforce, no movement.

Let me spell out the implications in the strongest possible terms. Muscle power is NOT the driving force. It is the intermediary force. It converts a downforce into a quasi-horizontal oscillation. The driving force—the thing that ends up as movement—is gravity. Muscle power (a.k.a. metabolic energy expenditure through muscle use) is what lets gravity end up as movement. Gravity could provide zero net energy (zip, nada) and still it makes sense to call it the “driving force.”

The important question to ask about running isn’t really whether one running technique “uses” gravity to run—all running necessarily does so. Let me be even more specific: all overground movement is a result of expending energy in order to convert some downforce into a quasi-horizontal movement. The degree to which movement occurs is commensurate to the degree to which the organism/machine is harnessing downforce in real time.

Running according to the tenets of The Pose Method gets you “free energy” from gravity in the same sense that a car that never fishtails also gets “free energy.” In other words, Pose offers the cheapest way, all things considered—speed, agility, endurance, resilience, performance consistency, performance frequency, metabolic flexibility, recovery, longevity, etc.—to convert as much downforce as possible into overground movement. The critical observation offered by The Pose Method, then, is about how the body’s “engine”—its musculature and various systems—work best to harness the force of gravity to produce forward motion.

If the car weighs too much for the engine, it stays put. If engine power exceeds grip, it spins out. In other words, car’s absolute theoretical speed limit on Earth isn’t set by the power of the engine, the design and engineering of the transmission, or the materials it’s composed of. The maximum horizontal speed that any object can achieve is set by the theoretical limit to which it can harness the few downforces available to it on Earth. Once the car’s power and engineering causes it to reach speeds at which it is impossible to stop the air around it from supercavitating (creating a vacuum around the skin of the car), no aero kit will allow it to go faster, and no further improvements to the drivetrain will do it any good.

Of course, unlike race cars, the human body is not set up to use wind as a downforce—and we couldn’t run fast enough to make it matter anyway. Our running speed is a function of our ability to harness one downforce: gravity.

For a runner, improving efficiency by harnessing the force of gravity can mean 2 things:

  1. Removing power leaks and other muscle use that does not contribute to harnessing gravity. (The race car example would be to swap in better and better parts, and to make sure that you don’t throttle up enough to drift the car).
  2. Increasing top running speed: a runner with good form (a.k.a a runner whose movements and stances maximize the harnessing of downforce) can do so to a greater degree—in other words go faster—than an identical runner whose movements and postures do not effectively harness downforce.

Note that #2 is a hidden efficiency: it only reveals itself insofar as the runner goes faster. Both the inefficient runner and the efficient runner may be using a very similar amount of energy at lower speeds, but only the more efficient runner can get to a faster speed.

Pit my Toyota Tacoma against a Ferrari. Both would perform quite similarly at lower speeds and wide turning radii. If you ask both of us to make a wide sweeping turn at 60 miles an hour, we’d perform almost identically. You’d say “Whoa! Correcting for weight, they’re equally as efficient!”

But this observation only holds at lower speeds. If you increase the speed to 160 mph and tighten the curve, my Tacoma would start to spin out or come off the track, forcing me to reduce my speed. In other words, even if you doubled the horsepower on my Tacoma, I wouldn’t be able to match the Ferrari because of its stiffer suspension, better tires, lower profile, and aerodynamic design (in other words, it’s much better at harnessing downforce).

I believe that the discussion of “saving energy through the use of gravity” is meant to help us recognize—for starters—that we move forward only to the degree that friction and muscle power meet. It also has a few other implications (to put it mildly), but those are best left for another post.



UPDATE: Check out what I’ve written on The Pose Method:

About Pose theory of movement in running.

About Pose theory of movement in all sports.

About the “unweighing” principle of Pose theory.

Strengths and weaknesses of analytic and synthetic thought, explained through tacos: The real “about this blog.”

About a year ago, Craig Payne from Running Research Junkie leveled a (fair) criticism at my blog in the comment section of another article: that I don’t do “analysis.”

Craig is right: I don’t (and I don’t claim to). Judged as analysis, much of my thought process on this blog is indeed poor. One of the reasons I don’t is because too many people in the run-o-blogosphere already offer excellent analytic thought—of which the highest expression might be Craig’s own blog.

But another reason I don’t offer analysis is because of an emerging field that is very dear to my heart: systems science (and specifically systems thinking).

So what is it that I offer here?

I offer synthesis.

Systems thinking—and other emerging fields that depend on its tenets (such as psychoneuroimmunoendocrinology, or PNIE)—are synthetic sciences. What they do is best is tell a coherent story about a system or supersystem by making sense of all of its features and bugs, strengths and weaknesses, to postulate an argument about its functional purpose: why it does what it does.

Run PNIE through tests that establish whether a particular form of analysis has value, and it will be found wanting.

It joins seemingly unrelated domains—the mind and the immune system, society and hormones—by telling a story about why it makes sense that they interact.

It factors in phenomena that create turbulence in the system (but by themselves have no lasting impact on the system at large) by suggesting how they could conceivably be interconnected through a  long line of effects on parts and properties of the system—some, like thoughts, emergent; others, like killer T cells, not.

(I imagine analytic sciences staring with incredulity at PNIE, thinking: “Are you insane?!”)

While a field like PNIE can produce a consistent narrative, what it cannot do is reconcile every specific variable with every other specific variable. Evolution, for example, is imperfect at best. It gerrymanders structures that performed one function at some point into structures meant to perform a different one.

Modern accounts of biology observe this basic evolutionary reality: human physiology, for example, is far from the physical consummation of the divine form, or the expression of cherry-picked mathematical constants (as alleged by the Classical paradigm). The human body is best described as a hodgepodge of systems and parts, twisted and tweaked by evolution to perform a specific function (or series of functions) at the expense of countless others.

We can’t rely on analysis of specific strengths and weaknesses to come to conclusions about what structures do. It just isn’t possible for the (decidedly imperfect) tales told by PNIE, systems thinking, and other synthetic sciences to have fewer imperfections than the gerrymandered biological structures they examine.

What analytic sciences ask for, synthetic sciences simply cannot give. For analysis, the devil is in the details (but so is everything else). For synthesis, while the details must be addressed, imperfections in the story do not always mean that the story is imperfect in and of itself. Instead, as long as the gestalt remains intact (in the face of newly discovered details), imperfections in the story may speak to corresponding imperfections in the structure it describes. 

Here’s a great example: tacos. As most of us know, the filling falls out of tacos all the time. Sometimes it falls out the ends. Sometimes the tortilla gets soggy and breaks apart. Even then, the general consensus is that the purpose of a taco is to hold stuff in (despite the fact that it can only do so imperfectly).

The story we tell about the taco—that its functional purpose is to hold stuff in—is imperfect: in just about every instance of eating a taco, stuff falls out of one. (To analysis, this seems paradoxical: these two realities about the taco seem to be contradicting the idea that the taco is meant to hold stuff in.) But synthesis shows us that the reason the story is imperfect is not because the purpose of a taco isn’t to hold something in. It’s imperfect because the taco is only imperfectly capable of performing its functional purpose.

This tells us something very important: just because a structure is meant for a particular function does not mean that it can (or should be able to) produce it perfectly. Trade-offs and inefficiencies do not mean that the structure was meant to produce a different function.

In other words, there are better ways to hold in the filling. For example, we can fold in the edges of a taco, but doing so alters its essential nature: we’ve turned it into a burrito. But it also isn’t the case that the burrito is the better taco, and that as such, taco vendors are just behind the curve. There are (at least) 2 specific advantages to preserving a food’s “taco-ness”:

  1. Versatility: By tolerating the disadvantage that a taco has a hole at either end, you gain the advantage of being able to stuff it with more veggies and sauce from end to end and still being able to pick it up without getting dirty. (Try re-folding a burrito that is already filled to capacity.)
  1. Modularity: By putting up with the fact that your basic taco shop will give you nothing but meat on a tortilla, you are able to go to the veggie and salsa bar and build it however you like. Depending on how good you are harnessing the (imperfect) modularity of the taco, you’re also able to (imperfectly) swap out any ingredients you may not like.

Similarly, the fact that an imperfect structure produces any given function with some degree of difficulty does not entail that the structure is not meant to produce some particular function in some particular way: A taco isn’t completely versatile, excellently modular, or perfect at holding stuff in.

Furthermore, the advantages that the taco holds over the burrito—versatility and modularity—were bought at a steep price: it’s ability to effectively contain cheap meats and vegetables pales in comparison to that of a burrito. But all those disadvantages and compromises don’t mean that those aren’t intended features of the taco, or that there aren’t gastronomical situations to which the taco is better suited than the burrito.

For the taco (like for the human body), convenience and function—instead of the pursuit of efficiency in a few arbitrary parameters—drive evolution. As Noam Chomsky said about human communication, “languages do best what people do most.”

(What they don’t do is what’s most efficient.)

In order to explain the cobbled-together, evolutionary Frankenstein monster that is the human body, we need to rely on a mode of thought that is not allergic to paradox—and attempts to reconcile it instead of simply describing it. (While plenty of paradoxes have been reconciled successfully within analytic sciences, doing so has always been the result of synthetic thinking.)

We need to become storytellers of physiology and bards of biomechanics. To describe what human bodies have been observed to do is as dour as it is noble. To spin a story of what this depressingly imperfect, infinitely complex machine is attempting to do—in all its flawed glory—is the endeavor I want to be a part of.



A much-needed disclaimer:  I recognize that Craig does not need (and probably doesn’t want) my opinion that his blog is the “highest expression of analysis.”

A second, much-needed disclaimer: I embark on this post sequence only because (1) I deeply care for these themes, (2) I believe that there exists a functional, coherent story to be told about running, (3) that’s what synthetic thought is built for, and therefore (4) it is my opinion that analysis par excellence is simply is not enough in our collective attempt to give a complete, functional account of the running human body.

The fact that most of what I do here is synthesis (and not analysis) is an issue aside from whether my attempts at synthesizing information—or anyone else’s—make any sort of sense. (But that’s a different issue.) But if, having read this post, you still tell me you believe that synthetic thought (or science) should play no part in explaining the human body’s function, I bid you a good day.

Speaking the body’s language: simplifying training stimulus.

As your understanding of athletic training becomes more sophisticated, one of the first concepts you come across is that of training stimulus. In simple English, training stimulus refers to what the body gets out of a particular workout.

Discussion of training stimulus abounds in circles that use MAF (Maximum Aerobic Function)—also known as the Maffetone Method—as their main framework for training.

The overarching mandate of the MAF Method is to protect the body. That is the best way for it to tolerate stresses, grow from training, and produce a great race performance. The party responsible for these functions is the body’s aerobic system, which oxidizes fats (burning them in the presence of oxygen) to provide a stable and long-lasting energy supply.

In endurance events, “protecting the body” means that the aerobic system must provide almost all the energy utilized during exercise. In power events, the aerobic system should be buttressing the function of the anaerobic system—which provides vast amounts of quick energy by burning sugars without oxygen—and still be strong enough to take charge for the duration of the recovery period.

For those who have already committed to developing their aerobic systems (by training at a low relative intensity), an issue inevitably arises: in long workouts that should occur theoretically at a low intensity, people accidentally (and often) end up rising above the desired intensity for a few seconds.

This brings up a crucial question: does this change the training stimulus?

There are several ways of answering this question. We can observe whether our speed at the aerobic threshold decreases after a month of training. We can go out and get a heart rate variability app that tracks our body’s autonomic readiness. We can even go get lab tested to see if our VO2 Max has decreased.

(If these terms mean nothing to you, don’t worry. Unless you’re an elite athlete who redlines for a living, they don’t need to. That’s the point.)

The body isn’t a black box. Action and circumstance affect it in ways that we can readily experience (when we know what to look for). A critical caveat: In this post, I’m only discussing the interpretation of experience before and after a workout. Using our subjective experience to measure and manage training stimulus in real time brings a whole other level of complexity.

Let’s abstract away from training for a second, and leave all that exercise terminology behind. Suppose you are on a long, leisurely birdwatching hike. You stop every few minutes to take notes, and you loiter every now and then with your binoculars as you try to make out the species of a bird in the distance. But 4 times over the course of this hike, you saw a novel bird just around the bend. Excited, you raced to take a picture.

How do you return from that hike? You are energized, renewed, invigorated. In spite of those few short sprints, the hike was a “low-intensity” experience.

Here’s another example: you’re back in your hometown after 5 years on a family visit. There’s been parties and get-togethers every day, and you’ve had ample time to catch up with all your friends.

But two things happened: the second day, you had the great misfortune of being mugged. And then the day after that, a former business partner caught up to you at a stop sign. He’s had a spell of bad luck—and in that short encounter, saw fit to threaten you and your family (over what you had thought was water under the bridge).

99% of the time, everything was pleasant and relaxing. But, for 10 minutes, the ground shook. That was enough for you to leave town with a new and unexpected wariness. Even the language—“two things happened”—tells you what the primary experience was.

This is also the case in athletic training. Put another way, the same body that has to glean meaning from that unexpectedly stressful visit (in order to be able to adapt to the next threat) is the same one that you take to the gym or out on the trails. That same body has to figure out whether it makes more sense to treat a particular training event as an “endurance workout” or a “strength workout.”

When a run feels “rejuvenating”—it’s very likely that’s exactly what it’s doing for your body. (The opposite holds true as well.)

You can break down the experience of being mugged in ever finer detail, and identify sensory and psychological stressors, and observe their physiological and neurological effects . . . but you don’t really have to.

Don’t get me wrong—you’ll get far more data about the effects of a divorce or a family vacation if you go get an fMRI every time something happens. That is a fact. (You can probably make better lifestyle choices when you know for sure whether your amygdala lights up when you see pictures of your former spouse.) But you don’t need an fMRI to be spot on—in a general sense—when asked what either experience did for your mental and physical health.

You can say the same about phenomena such as autonomic readiness (of the nervous system), which contributes to produce our subjective feelings of readiness for a wide variety of tasks.

Our experience of readiness doesn’t just happen to co-occur with our physiological readiness. Look at it from an evolutionary point of view: we didn’t have heart rate variability apps or monitors “waaay back when.” Our experience of readiness has to emerge from the fact that our nervous system, metabolism, hormonal system, and motor capabilities are actually ready for whatever it is we feel ready for. This is essentially the same line of argument that Tim Noakes (in his immortal book Waterlogged) uses to argue that the best measure of physiologically relevant dehydration is the subjective experience of thirst.

(In the same book, Noakes also argues that the fact that this even needs to be argued shows just how disconnected from the obvious we’ve become.)

If the subjective and the physiological weren’t part and parcel of the same system (to say that they’re “linked” is a gross misrepresentation), we’d all be dead. In other words, our heart rate variability monitor isn’t really going to change until we feel ready—and if it does change but we still don’t feel ready, we can be quite sure that there’s some other measurable physiological parameter out there that explains why.

The biggest mistake we can make is to listen to our pet parameter while disregarding the conclusion of a built-in measuring device capable enough to have outcompeted every other life form on the savannah—a device without which Neil Armstrong would have made it to the orbit but not the surface of the moon.