Tag Archives: systems thinking

Biomechanic Issues

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

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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 Economy, and 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 aerobic system, Training Ideas

Strategizing Stress, Part 1

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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.

 

Principles of Training, Thinking in Systems

Is there really a difference between “injury-prevention” and “training specificity”?

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A lot of us are familiar with sports specificity: you tailor your training to achieve greater performance in individual sports. Some of us go as far as being “event-specific.” We train trails for trail running events. We practice running the inclines and hill lengths we’re likely to encounter during the event.

But I think that we can take the concept of training specificity a lot further: particularly as it pertains to the realm of injury prevention.

What does an injury mean from the perspective of athletic competency? It means that there was some stress, supposedly germane to the sport, that the body simply could not tolerate. Presumably, this is a stress that the body can (and should) adapt to.

I’m not talking about obscene stresses such as the micro-concussions that have been shown to cause brain damage in football players. I’m talking about simpler things: dehydration and hypoglycemia after a marathon, shin splints, etc.

Let’s take shin splints, for example. Shin splints are reputed to occur due to the repetitive stress associated with running. Shin splints—and the subsequent stress fracture—cause people to lose training time and training quality, increase the overall stress of training, etc.

My point is this: an inability to cope with a particular stress (resulting in an injury) is a bottleneck to development.

If an injury prevents a runner from improving, or puts their athletic future at risk (and it does), then injury-prevention should be at the very top of the priority list. Put another way, injury-prevention is the ultimate sports-specific training: it means training the body not just to get better at the sport, but to train the body to handle the basic stresses associated with the sport.

This is a difficult proposition for many people: it is different on a case-by-case basis. The same symptom (shin splints) can have a multitude of causes. When the issue is the amount of stress, increasing lower-leg strength by itself can solve the problem. But others may need to fix an imbalance between the front and back muscles of the lower leg, for example. Others yet may be erroneously unburdening the big calf muscles by giving the job of knee flexion entirely to the hamstrings.

Failure to address any of these issues can dramatically reduce the training response: tighter muscles and less mobility means less neuromuscular feedback. But a higher heart rate is necessary to drive stiff (and weak) muscles. This means more stress. And because some muscles are stiff, the body geometry is disadvantageous: it isn’t going to align itself (or remain aligned) with the primary vectors of force.

Fixing any of these issues will allow the body to learn from and adapt to the sport. Ultimately, I believe that the runner who “paradoxically” spends time correcting muscle imbalances or strategically strengthening bone, muscle, tendon, and connective tissue—and running less miles because of it—will need to run far fewer miles to observe the benefits of training.

We need to make the choice to not merely roll out our tight quads or hip adductors after the fact. I think we need to address the underlying cause of that tightness (a process which may or may not include myofascial release). And I think that we need to put this within the larger context of our training and racing: in no way does injury prevention or rehab constitute “taking time off” from training.

Preventing injuries and doing the rehab is a much better—and more honest— example of “training the body” than going out and slogging miles that are just going to put us back on the table. In every way that matters, we’re doing the training that our body needs, right now.  Tomorrow, we’ll be able to go out and do the training we want, and achieve the effects that we want.

And how much happier, faster, and healthier would we end up if we can trick ourselves into wanting to do the training our body needs?

Linguistic Traps

Runners: Let’s not confuse Efficiency with Optimization

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We should always be careful, as runners and athletes, when shopping around for new data to help us develop our craft. We should be even more careful when this data comes in a convincing format—scientific research—and alarm bells should go off when that research isn’t put in context.

Recently, I went to take the Pose Method Level 1 coaching certification, which I wrote a pretty popular review about. With this post, I want to begin diving a little deeper into the subject, starting by addressing one of the major scientific critiques towards the outcomes of minimalist running, forefoot striking, and the Pose Method: that these techniques are less efficient than heel-striking—namely, that they use more energy across the same distance.

Well, do they? Perhaps. Most likely, in fact.

However, seeking sheer reductions in energy use may be missing the point.

Let’s take a popular sport as an example: mountain biking. One of the first things you consider when buying a new mountain bike is whether you want dual suspension, or only on the front. This is a classic trade-off: the dual suspension lets you go on more rugged terrain, but it also means that less power from every stroke goes into driving the bike forward.

A dual-suspension bike is less efficient than a front suspension bike. That’s it, right? Front suspension bikes are superior. It’s a done deal.

Well, no.

Before I go on, let me be quite clear about the argument that I’m making. I’m not saying that less efficient options are better. I’m arguing that different options can’t—and shouldn’t—be judged on efficiency alone. I’ve seen it at least a few times in the running community: the studies on whether the Pose Method lowers running efficiency are presented in one stand-alone sentence, as if by itself, and without regard for the scope and depth of functions that the human body must fulfill, efficiency means something.

Efficiency alone means nothing. The questions we should ask is: what is it getting us, and what are we sacrificing by pursuing it?

Let’s go back to the mountain bike example.

Adding that rear suspension increases the capability of the bike to interact with more rugged terrain. If you land from a high jump with a dual suspension bike, you’re less likely to break the frame—or yourself.

Not a mountain bike, but I'd say that Danny MacAskill's legs count as suspension 1 and 2.
Not a mountain bike, but I’d say that Danny MacAskill’s legs count as suspension 1 and 2.

You’ll see this across all systems: increasing the dynamism of any system (which means both its capability to interact and its rate of interaction) increases its ability to interface with other complex systems (i.e. the environment). In order for this to happen, a dynamic system has to be working with sufficient moving parts, all of which take energy to function. If we just focus on cost-cutting measures—what gets me the least energy consumption, all else aside—we’re going to be undercutting that system’s optimization at some point.

That certainly seems to be the case in human locomotion, as suggested by this study (also cited above).

We’re making a very specific—and very generalizable—trade by adding a rear suspension to the mountain bike: we’re reducing its efficiency in order to optimize it to the environment.

Lowering the efficiency, however, does not immediately mean that you’re optimizing something. In fact, it’s typical to find that if optimization drops below a certain threshold, so does efficiency. A bike needs intact tires to function well. You can’t be riding on the rims during a race and expect to be very efficient.

Optimization, although more costly in the immediate term, is more cost-effective than hard-edged efficiency over the long-term. What happens if the bike frame breaks? The amount of power that goes from your downstroke and into the ground drops to zero.

We all live in this compromise: we want to increase our efficiency, but not at the cost of optimization. Let’s use a gait example. Is it more efficient to shut off your gluteus maximus, hamstrings and quads while running? Probably—those muscles are huge. They’re consuming lots of sugar and oxygen in order to stabilize the pelvis and move it over the femur and the knee joint.

In addition, they’re mostly only active from contact to midstance. They’re the biggest muscles in the body, and they don’t even help you push off. Less efficient? Sure! Why not just let momentum carry your GCM—general center of mass—over your knee joint while keeping the hip extensors quiet?

Because your femur would summarily come off your tibia, and your patella would pop off and land somewhere on the ground in front of you. Once again, the efficiency of your gait would drop to zero.

I’m not making an argument for any particular method or stride type. (I believe those arguments are there to be made, once we have satisfactorily defined what we mean by “stride type,” but not in this post). The takeaway, as I mentioned above, is that in order to optimize something to the environment—say, in order to allow our body to remain in a configuration which can adapt its footfalls to variable terrain—we’re going to be sacrificing some raw efficiency.

Is forefoot-striking or Pose the best way to optimize the body? Well, that’s a different question.

UPDATE: In this article, “Pose” refers to excellent pose technique. (This was brought up by a concerned reader on a Facebook thread.) Indeed, all running and all movement is an alternation of poses (think about the kata in martial arts). For better or worse, the question remains in the scientific and running communities: is excellent Pose technique the best way to run? Many try to detract from it by saying that it is less efficient. I believe that regardless of whether it is or not, that line of argument largely misses the point.

Principles of Training

Deconstructing the Plateau: Part 2

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When our athletic ability plateaus, and we no longer see the gains in speed, strength, or endurance that we used to see before, we tend to increase our training volume: more hill repeats, more squats, more miles.

Training like this is rarely the right answer. The human body is a phenomenally complicated system—those of us who have been chronically overtrained and injured know that for a fact.

Obvious, straightforward approaches aren’t enough for a system like this. Sure, there are parts that are plainly related to particular abilities: fast-twitch muscle fibers, sugar and ATP to speed, slow-twitch muscle fibers, lungs, fat, and mitochondria to endurance, and muscle size and maximal effort to strength. But ultimately, we need to appreciate the behavior of the system as a whole, and tailor our training to the system as a whole.

If we want to achieve this, there is no idea more important to understand than the systems thinking notion known as emergence.

Emergence addresses the fact that a whole is larger than the sum of its parts: while the parts of a particular system, whether they be atoms, muscles, cars, or people, have properties of their own—atoms are vibrating at certain rates, muscles can be strong or weak, cars can be fast or slow, and people can be skeptical or not—when you put these parts together into a system, you get properties that apply only to the system, and not to the parts.

In other words, these properties emerge from the interaction of the parts, and therefore, of their organization into a system.

These are called emergent properties.

Solidity, for example, is an emergent property. A liquid becomes a solid when the molecules that compose it get colder (and therefore closer together) and move beyond a certain temperature threshold. Nothing happened to the molecules themselves. But the changing nature of their interaction changed a property that expressed itself in the system of molecules: that system went from being a liquid to being a solid.

In the same fashion, speed, strength, and endurance are emergent properties of the human body in the athletic domain. How so? Even if one muscle is strong, fast, and possesses good endurance, it can’t express that speed, strength, or endurance unless the rest of the body’s faculties—opposing muscles and circulatory, endocrine, and nervous system, to name a few—are also functioning properly and interacting correctly with each other.

What does this tell us?

That the particular capabilities of particular muscles or internal bodily systems don’t matter as much as the proper interaction between those systems.

To develop greater endurance, it is not enough, for example, to train simply the aerobic engine (even if you think of the “aerobic engine” as comprising the lungs, blood vessels and capillaries, diaphragm, all the way down to the mitochondria). Bone, tendon, fasciae, and even the fluid sacs around the joint must be developed enough to withstand the added use made possible by a more powerful aerobic system.

Without developing these systems—and others—together with each other, and ensuring that they are equally balanced and capable of interacting with each other at the highest level of performance, we’ll see our increases in athletic ability slowly grind to a halt.

Why?

In a previous post I mentioned how different variables—say, the power of different bodily systems—go from being apparently unrelated to being frustratingly interrelated as we develop the system’s capabilities:

“The perceived set of independent variables changes to a formidable set of interdependent variables. Improvement in one variable would only come at the expense of the others.”

-Jamshid Gharajedaghi

That is essentially what is happening here: as we develop the cardiovascular system, the musculoskeletal system, or the nervous system, we find that further increases in our cardiac output, muscle power, or ability to concentrate lead us down a problematic path. If we develop too much capability in one of these domains, without training others, we’ll end up creating conditions—like running too many miles on untrained calves—that will end up destroying our athletic ability.

But there’s more to this than just training each given component, and more to it than even training them to match each other’s capabilities. As I mentioned above, systems aren’t really built from parts; they’re built from interactions. So we must train the ability of the different parts to interact with each other.

To name one common example of what happens when we don’t, there is the Valsalva manuever, which consists of holding our breath when we exercise. We do this because of a dysfunction of the deep muscles of the hip and the spine, and their inability to work together with the diaphragm. The Valsalva manuever can raise thoracic blood pressure to dangerous levels, and put the athlete’s life at risk.

It is typical to see runners with hip/spine dysfunctions hold their breath every few steps, or time their breath to the landing of a particular leg. This has the potential to exacerbate a whole bunch of gait problems, not to mention the loss of speed, power, and endurance, and the effort implied in having to overwork the lungs to make up for the dysfunction at the hip and the spine.

This, or some form of it, is typically why as runners and athletes we plateau. We can’t move forward with our development: the components themselves are preventing each other’s ability to evolve.

The underlying problems must be resolved, but above all, the functioning of these systems must be synchronized. They must interact; their functioning must assume that the other system is also at play.

When we achieve this with more and more of the body’s components we will observe dramatic increases in the emergent properties of the athletic body: speed, strength, and endurance.

Principles of Training

Deconstructing the plateau: part 1

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All too often, as runners and athletes we hit a “plateau”—a period of time where we don’t improve, and where increased training seems to shove us into a downward spiral of overtraining and injury. Rinse and repeat. Thanks to our own overactive imagination, or to the whispers of the running superego, we conclude that it’s our genes. Our genes just won’t let us. Continue reading Deconstructing the plateau: part 1 →

Obesity

The systemic nature of obesity, and a few of its socio-economic feedback loops.

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As part of the systemic explorations of athleticism on this blog, it’s time to begin addressing the topic of obesity. Let me begin by stating that obesity is not, as many believe, a reflection of someone’s character, or caused (and maintained) by a lack of willpower. It is largely a systemic issue, meaning that in our current socioeconomic structure, there are a multitude of processes that contribute to the creation and proliferation of obesity in particular populations.

In fact, the evidence that obesity is systemic begins with the fact that it is much rarer in affluent (white) populations than it is in minorities, the disenfranchised, and the oppressed. If it was an issue of willpower, then we’d see no such social, ethnic, and economic disparity between populations.

As with all systems, society and the body both work in terms of feedback loops—processes that link with other processes in order to achieve a particular function. A typical example of a feedback loop is a thermostat: when the temperature in the room rises, the air conditioning kicks in. Once the temperature drops, the thermostat shuts down, allowing the temperature to rise again. One process (the rising temperature) “feeds back” into the other process (the thermostat/air conditioning), creating a loop.

thermo 1

In order to diminish the expression of obesity in a population, the relevant feedback loops have to be understood. One such loop is created by the following factors. The high prices of unprocessed foods often make them prohibitively expensive to the poorest populations, who often have to work longer hours in order to make ends meet. With no time for visiting family, let alone constant, rigorous physical activity, people develop metabolic problems and gain weight. However, because obesity is perceived to be a product of laziness or poor character, the person often loses social capital. With this loss of social capital, the person loses job opportunities to slimmer, fitter individuals of “better character,” solidifying their poverty and destroying any possibility of change.

ob loop 1

There are other biological factors to be taken into account: because stress itself often leads to weight gain, the lack of free time for most working adults can also contribute to the expression of obesity. Social stresses, such as the pressure to exercise or diet, created by well-meaning yet ignorant people that are sure that all these people have to do is “go work out,” can not only destroy motivation but also directly increase someone’s weight gain.

ob loop 2

Try getting out of that system. And it’s only part of the story.

Of course, none of this means that conceivably, obesity cannot be caused by a loss of willpower or poverty or character. But what the systemic analysis does is illustrate that overwhelmingly, the most powerful contributors to the obesity epidemic are not inside the person (whether they be genetic or psychological). They are outside, in the socioeconomic system, or created by outside forces inside the person.

The last thing we should do to someone struggling with obesity—or someone who isn’t struggling and just wants us to get the hell off their back because they’re okay with themselves, or someone who in fact isn’t obese (or otherwise unhealthy) and just looks fat to our untrained eye—is suggest them to change or expect them to change.

Perhaps the biggest social contributor to obesity is ignorance of systemic factors, and of systems in general. And it isn’t the ignorance of those who suffer from obesity, but the ignorance of those who don’t. For example, even though obesity is characterized by an increase in body fat, body fat alone does not signal obesity. This is a condition in which the person’s metabolism is working against itself, putting on too much fat to maintain health and mobility. Unless those conditions are met, body fat is just body fat.

Unless we know that this “added” body fat is impinging on someone’s health to a certain degree, we can’t know that they are obese. Most of the time, people who look chubby are completely healthy. However, to those of us who have associated fat with obesity—and to those others who use a lack of body fat to gain social capital—this is a disagreeable state.

But some differences really are only cosmetic. Ignorant, yet well-intentioned comments or suggestions will do a majority of people very little good. Often, all they really do is entrench our own ignorance (since we leave the interaction so smugly sure of our knowledge) and distance ourselves socially from the person we commented on.

Casting attention on a feature that is socially disadvantageous (but not disadvantageous in terms of health) shines a light on how we don’t have that “problem,” whether we want to or not. Our social capital increases, whether we see this or not, and that benefits us, whether we understand that or not. Those actions only solidify the argument that because obesity creates body fat, body fat is obesity, and therefore fat is bad.

Unsolicited advice has systemic repercussions. By itself, even if it’s accurate—or rather, especially if it’s accurate—unoslicited advice can worsen the problem.

Something we could do is help remove the systemic factors contributing to obesity, including the social pressures to be thin. This is not to say that obesity is okay.  Obesity is a metabolic disorder whose effects seriously encroach on people’s quality of life, particularly towards their senior years. We’ll never get around this fact. But just trying to help isn’t enough. The ignorance that leads to “helpful” comments and suggestions really only exacerbates the problem. The road to hell is paved with good intentions. Only in the case of obesity, it’s usually us paving the road, and it usually leads to somebody else’s hell.

Biomechanic Issues, Thinking in Systems

The “heel-striking” running gait doesn’t observe the requirements of the human body’s mechanical paradigm.

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Those who say that the midfoot strike is the “ideal” running stride often conclude that midfoot striking is “better” for a variety of reasons. One of those reasons is that, allegedly, the midfoot strike is more “natural” than the rearfoot-strike (also known as the heel-strike).

It’s a bad idea to call the midfoot strike more “natural”—aside from the fact that the allegation is wrong: humans use a variety of different footstrikes for a variety of different activities. Rearfoot striking ahead of the center of gravity is the default walking strike. Rearfoot striking is also used to abruptly halt forwards momentum, and sometimes, to turn by using the heel bone as a pivot. Conversely humans use a very anterior (forefoot) strike during the acceleration phase of sprinting.

In short, the problem with this “natural” argument is that human feet strike the ground all over the foot map.

So stop calling it natural.

Which is why I prefer to adopt a more technical term: paradigmatic function. This term means that a certain function X is more in line with a particular structure, or a particular configuration of a structure.

For example, variable-geometry aircraft—those which have the ability to “sweep” the wings back from an extended position to create a triangular shape (such as the F-14 Tomcat)—use the swept-back configuration for combat and supersonic flight, while they use the extended (regular) position for takeoff and landing. For the F-14 Tomcat, the paradigmatic function of the extended configuration is takeoff and landing, whereas the paradigmatic function of the swept-back configuration is combat and supersonic flight.

tomcat

Although it is no doubt possible for the F-14 to land with the wings swept back and enter combat with the wings extended, there are two things to consider: (1) each configuration works better for each activity, meaning that (2) each configuration “solves” a different problem: the swept-back configuration allows for greater maneuverability and speed, while the extended configuration allows for greater stability and reduced speed during landing.

Central to systems thinking is the idea that every system (or configuration of a system) is built to solve a particular problem. For example, a system with a branching structure, like a tree, a lung, or a network of roads, solves the problem of getting the maximum amount of energy or nutrients to and from various places with the least amount of effort. The shapes of systems always correspond to the most parsimonious way to solve a particular problem. In a very real way, you can think of all systems—and each individual configuration of those systems—as solving a problem that is specific to each system or configuration.

The very same goes for walking and running, the two important gaits—the two functional configurations—of the human body.

Although it would seem easy to say that these two functional configurations are “walking” and “running,” it’s better to get at this conclusion in a more roundabout way:

In terms of the stresses absorbed by the body, the most important difference between walking and running is that in running, there is a flight phase, while in walking, there isn’t. This means that one of the things that the body needs to do while running is absorb the shock of landing, while in walking, this particular need is largely absent.

This theory is largely borne out by looking at the muscles used during walking: the largest muscles in the body—the gluteus maximus, the psoas major, and the hamstrings—are largely inactive.

Because of this, the knees remain locked during the walking gait. This means that by walking, the body “solves” the problem of preserving energy while remaining in motion; that’s what the walking configuration is for.

Because a necessary component of running gait is the absorption of shock, the landing portion of the running stride should incorporate a shock-absorbing motion. So, in order to figure out what kind of motion comprises the landing portion of the running stride, let’s review what a “purely” shock absorbing motion looks like: landing from a jump.

When we land from a jump, our hip and leg mechanism works largely like a shock-absorber: we land on our midfoot or our forefoot, and all the joints of the lower extremity go from a lot of extension to a lot of flexion in less then a second, meaning that the hip, knee, and ankle all flex together. (This is known as triple flexion). This means that the paradigmatic function that the body uses to absorb shock is triple flexion. Similarly, in order to jump again, the body extends the hip, the knee, and the ankle simultaneously (which is known as triple extension).

Exchanges_Triple-Flex-Ext

In order to create triple flexion and triple extension, the body must recruit the largest muscles of the body, including the hamstrings, gluteus maximus, psoas major, and quadriceps. In other words, the triple flexion/extension configuration solves a very different problem than the one solved by walking: it allows the body to safely absorb the energy of impact, while powerfully exerting force against the ground.

Because running necessarily has a shock-absorption component and a takeoff component (because of flight time), it stands to reason that, during running, triple flexion and triple extension should form an integral component of the contact and pushoff phases (respectively).

This is where it gets problematic. The typical heel-strike (overstriding with initial rearfoot contact) plays out very differently from triple flexion: as the foot strikes the ground, the knee is mostly locked but the leg is stretched out in front and the foot is raised. The hip is in flexion, the knee in extension, and the ankle in flexion. This means that the shock absorption capabilities of the leg are reduced—and because the leg flexes less, it has a lower capacity for pushoff.

heel-striking

(The lower achilles tendon loading of heel striking as compared to forefoot striking may attest to this).

I’ll leave the issue of heel-striking under the center of gravity for another post. For a taste of why it might be problematic, try jumping up and down in the same spot while landing on your heels. It’s extremely difficult.

In contrast, the midfoot/forefoot strike is a great example of the triple flexion/triple extension principle at work: When you land on your midfoot, your leg compresses like an accordion: the ankle, knee, and hip create a zig-zag shape, which straightens as you push off. Midfoot striking adheres strongly to the musculoskeletal configuration used for shock absorption/propulsion movements.

forefoot-striking

In my opinion, the best way to know if you “are” a heel-striker in some essential sort of way is to jump up and down, and to see if it is easier for you to absorb shock by landing on your heels than by landing on your midfoot or forefoot. (Unlikely). If that isn’t the case, and yet you heel-strike while running, it might be time to look at muscular imbalances and power leaks, particularly in regards to muscular interactions at the hip area (illiopsoas, lower back extensors, gluteus maximus, quadriceps, and hamstring).

And then, embark on the long road of responsibly changing your gait.

Biomechanic Issues, Defining our Terms

A question of systemic resilience: is it more “efficient” to run shod than barefoot?

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The idea that running barefoot offers a metabolic advantage over running shod may be an “appeal to nature” fallacy.

Although some studies have found that running barefoot is actually “more efficient,” there have been a host of other studies that contradict those results.

So we can’t say for sure.

In a 2012 study titled Metabolic Cost of Running Barefoot Versus Shod: Is Lighter Better?, Franz et. al. set out to debunk the claim that barefoot is indeed more efficient. In a nutshell, their results found that not only did barefoot running have no metabolic advantage over running shod, but actually seemed to be more metabolically costly to do so. It has been suggested by several studies that the reason for this added metabolic cost is because of a “cost of cushioning.” According to these studies, the body is making an effort to absorb impact when running barefoot, that it doesn’t make when shod (more on this later).

I largely agree with the research question, experimental design, and results of Franz et. al. But reading this article stirred up several theoretical issues that don’t have much to do with the article in particular, but are important in terms of how the shod/unshod and hindfoot/forefoot striking debates have unfolded, particularly regarding what the terms “efficiency” and “better”—as in the title of the study mentioned above—have come to mean in this debate.

Franz et. al. begin the article by writing that “advocates of barefoot running claim that [barefoot running] is more “efficient” than running in shoes.”

First I’ll address the question of what we mean when we say “efficiency.”

It’s important to be clear that the advocates that Franz et. al. cite (Richards & Hollowell, authors of The Complete Idiot’s Guide to Barefoot Running and Sandler & Lee, authors of Barefoot Running) are using the classical definition of “efficiency” as do Franz et. al.—meaning that they claim there is a lower energetic cost to barefoot running. That claim may well be a fallacy, and Franz et. al. are right to debunk it.

But I want to draw attention to a different use of “efficiency,” which will eventually get us to analyze what we mean when we say that one function (say, shod running) is better than another (say, barefoot running). In order to do this I need to bring in one of my favorite concepts from systems thinking: resilience.

One of the hallmarks of a resilient system is that it is built out of many tightly-coupled feedback loops, which basically mean that there is a lot of movement and interaction between its various parts. And for that movement to exist, the resilient system must be spending larger quantities of energy than the less-resilient system.

(This idea is rooted in thermodynamics: the movement of molecules and atoms correspond to the amount of energy stored in a certain space, i.e. the temperature of that space). The idea that greater movement can only be produced by a greater use of energy is generalizable to basically everything.

Note, however, that the causal relationship between resiliency and increased consumption of energy only goes one way: all other things being equal, a more resilient system must be using more energy than a less resilient one, but a system that uses more energy than another is not necessarily more resilient.

In the classical definition of “efficiency” that Franz et. al. and the barefoot running advocates are using, the resilient system is less efficient—i.e. it is at a metabolic disadvantage, since it uses more energy—than the non-resilient system. It isn’t very useful to speak in terms of “efficiency” when we’re talking about complex behaviors like athletic performance: for example, when the body finds itself in crisis, it will begin shutting down major organs to conserve energy. And for every organ that it shuts down, the less resilient it is: it becomes less and less able to cope with new and unexpected crises. Is this more “efficient” in any reasonable sense of the word but the classical? Not really.

“Efficiency” in the classical sense has never been the goal of human running. In Waterlogged, Tim Noakes explains how running on two legs has a much greater metabolic cost, across the same distance, than running on four legs, and yet, because humans run on two legs, we are capable of running down antelope and other ungulates in the desert. (The advantages that running on two legs offers are thermodynamic, but that’s a story for another time).

Simply stated, if efficiency was what the human body wanted in the first place, we would have never gotten off all fours. Actually, we would never have become runners at all. But we did. So there has to be more to this story. By standing on two feet, there has to be another problem that we were trying to solve beyond “efficiency.” That problem is most likely how to be resilient in the performance of particular function: human endurance running.

The human body—like any system—has other goals beyond pure efficiency. Indeed, one of the primary goals of the human body is redundancy. Studies have shown that even when we exercise at maximal intensity, only a fraction of our sum total muscle fibers are recruited. In the classical sense of “efficiency,” you could say that it is less efficient to be redundant, since more energy and nutrients must be spent building these redundancies instead of using them for athletic performance.

All of this gets us to what we mean when we say “better.” In a very real way, (and for a variety of reasons), it isn’t “better” for the human body to be “more efficient” in the classical sense. It’s better for the body to be more redundant, and more resilient. In theoretical systemic terms, the fact that the number of active “feedback loops” increase when  running barefoot—since the touch receptors on the soles of our feet “feed back” information to our muscular system, which works to decrease impact—is indicative of the likelihood that the unshod system is more resilient than the shod system.

touch rec m

Furthermore, when we blow up the term “efficiency” onto the large scale (divorcing it from its classical meaning), we can ask ourselves: in time and energy, what are the advantages of protecting the system, over not doing so? According to the literature, wearing shoes doesn’t protect the system in its entirety, beyond the skin on the sole of the foot: It has been shown consistently that shoe cushioning doesn’t affect peak impact force, only our perception of that impact. Peak impact force is alleged to be the main cause of repetitive stress injury in runners. While it has also been shown that in hindfoot-striking, shoe cushioning decreases loading on tissues), loading is a very different issue, with different consequences to injury, than impact.

Given that running shod reduces the activity of our cushioning mechanism, it would be extremely informative to do a long-term study on the amount of impact absorbed by the tissue (as opposed to loading), when the cushioning mechanism is deactivated. (Short-term studies already provide evidence that impact forces are indeed reduced when running barefoot as opposed to running shod). In turn, it should be explored how the increased impact translates to tissue damage, recovery time, and ultimately time not spent developing athletically.

In these terms, we may yet discover that it is more “efficient” for the body to run barefoot than shod. Being this the case, we could say that it is “better” for the system to run barefoot than shod.

Whether this is actually the case remains to be seen. What we can do at this point is to observe how our words shape our perception, attention, and inquiry, and what it is that systemic insights can bring to the table, both theoretically and with an eye towards future experimental research.

Biomechanic Issues

A functional argument in favor of midfoot striking: putting the research in context.

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The human body is a machine with particular characteristics. So is a car. Just like the many different makes and models of cars have slightly different capabilities, human bodies are all different.

But they are not that different. For example, the operational requirements for all cars are very similar: the centrifugal force generated during a turn must not exceed the friction generated by the tires. And they are the same in humans.

But that’s not the way in which much of the medical and sports science literature treats it. Don’t get me wrong: everybody is in agreement on what the individual parts do: the gluteus maximus abducts and extends the hip; the gastrocnemius points the foot, etc. But there is a vast amount of disagreement as to how these parts are supposed to work together. Rather, there seems to be quite a bit of agreement that for the same systemic function (running), the individual parts can be performing wildly varying functions, and yet the system will still be somehow performing correctly.

I am, of course, talking about the footstrike debate. Before I continue, let me be clear that by “heel-striking” I don’t refer to how the foot hits the ground. I refer to the set of gait characteristics that contribute to overstriding by reaching forwards with the leg and striking the ground heel-first. The same goes with the gait characteristics associated with midfoot striking.

I’ve been reading a series of articles that associate different patterns of loading with different stride types. For example, a heel-strike is typically associated with increased loading of the knee, while a forefoot or midfoot strike is typically associated with an increased loading of the ankle and achilles tendon.

Most of the articles that I’ve read tend to conclude that therefore, we should see greater knee injury rates for heel-strikers, and greater achilles injury rates for forefoot/midfoot strikers.

However, that’s a hypothesis. By this I mean that thus far I’ve found no studies that have shown that these hypothesized injury rates actually occur.

The question is this: are all tissues equally amenable to loading? In principle, absolutely not. Buildings often have central support structures to carry the load. So does the body. The question is whether, say, the presence of the achilles tendon—a dense, springy structure capable of storing massive amounts of potential energy (also the largest tendon in the body)—makes the ankle more amenable to loading than the knee.

In principle, it makes sense that the presence of the achilles allows the ankle to be loaded more than the knee. However, this remains to be ascertained by future studies.

For now, what we can say is that the differences in loading associated with one foot-strike pattern aren’t “equal” to another. Because certain structures are paradigmatically employed by the body to support weight, absorb shock, and store potential energy, a foot-strike pattern that offsets loading to these structures will, in general, be more amenable to the overall health and functional performance of the body. Whether experimental research ascertains that the achilles tendon is such a structure remains to be seen.

However, I certainly agree with the general supposition that a stride type that places more emphasis on loading of the achilles tendon (such as midfoot striking) generates a higher incidence of injury for that structure. Across a population, use of a particular structure will almost necessarily correspond to an increase in injury and overuse rates of that structure.

It remains to be experimentally ascertained whether a stride type which offsets loading onto dynamic structures (muscles) and energy storage structures (tendons and fascia), will, across a population of individuals, create lower overall injury rates despite the likely increase in injury rates due to simple use of those structures.

However, we can still make a systemic analysis.

Let’s use the example of an airplane as an analogy: it is much more efficient for an airplane to use flaps, than to not use them. By increasing the total wing surface, flaps allow landing and takeoff velocity to decrease by a significant amount. An increased use of flaps will no doubt mean that, overall, more flaps will become damaged and broken than if flaps weren’t used at all. But because flaps help reduce the speed at which the aircraft lands, using them contributes to a decrease overall structural stress and damage associated with the impact of landing.

You could even make the argument against using flaps by saying that increasing the wing’s surface area will put more stress on the wing housing and the airplane’s airframe. Even though this is the case, making this argument misses the point. The point of the airframe—and especially of the wing structure—is to absorb the increased stresses associated with increasing the wing surface. Flaps should be used during landing regardless of the fact that both stresses to the wing and incidences of damage to the flaps will increase.

Along similar lines, if we posit that a certain body structure has a certain function, such as the achilles as a structure to store mechanical energy, the gluteus maximus as the main driver of hip extension, etc., then, under optimal conditions, the body should preferentially load the achilles upon landing and put the burden of moving the leg on the gluteus maximus. (All of which seems to agree with the findings of this study):

“When compared to RFS (rearfoot strike) running, FFS (forefoot strike) and BF (barefoot) running conditions both resulted in reduction of total lower extremity (leg) power absorption particularly at the knee and a shift in power absorption from the knee to the ankle.”

All of this said, the systemic analysis of the body is simple: in systems thinking, you look at the functions of different parts, in relation to the whole, to ascertain their function. The achilles tendon seems to be primarily a shock absorber. It certainly works that way when jumping—that’s why it’s almost impossible to land on your heels when you’re jumping straight up and down. So, any stride type that uses the achilles tendon as a shock absorber will likely be more amenable to the body.

Until evidence otherwise settles the matter—and only until then—the most reasonable conclusion to make is that a stride type that uses load-bearing structures to carry weight, offsets torque (rotational force) to joints that can rotate dynamically, uses shock-absorbing structures to absorb shock, and employs energy-return structures to return energy, are “better” than stride types that do not. Given the evidence currently in the literature, everything seems to point to (but not prove) the idea that midfoot striking is an example of the former, and heel-striking is an example of the latter.

AN IMPORTANT CAVEAT: The body is a dynamic system, which means that you can think of it this way this way: if you change one thing, such at the angle at which your foot touches the ground, three other things will change along with it. Perhaps you’ll see a change in your forward lean, a change in your hip extension moment, and therefore a change in the loading of a variety of muscles. In other words, you can never change only one thing. If you oversimplify your understanding or implementation of the changes you need to make in order to be faster, more efficient, or less prone to injury, you will end up being slower, less efficient, and more prone to injury.

This is why it’s important to talk about forefoot striking, midfoot striking and heel striking as “types of gait” and not as “types of footstrike:” the angle at which the foot hits influences (and is influenced by) a variety of other factors. My contention (which I believe is also the contention of proponents of midfoot striking) is that for a supermajority of people, the resolution of all of the biomechanic factors surrounding injury, muscle imbalance, power leaks, and resolvable musculoskeletal asymmetries, will result in the adoption of a midfoot/forefoot strike.

Again, whether this is actually the case has not been borne out by research.

I’d love to read what you have to say about this. Please put your comments, criticisms, and questions in the comments.