Tag Archives: foot-strike

Biomechanic Issues

Athletic performance is not about efficiency. It’s about power.

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One of the most oft-used pieces of artillery in the debate of minimalism versus maximalism, forefoot versus hindfoot, and barefoot versus shod, is the discussion of efficiency. Numerous studies have come out that rank the efficiency of these running types against each other, and consistently find that shod/hindfoot/maximalist tends to be more efficient.

(For the record, I think that the first camp that made the efficiency claim was the barefooter/forefooter/minimalist one. For reasons discussed below, that was a bad call).

Anyhow, it’s time to put this discussion to rest: Better athletic performance has never been a function of efficiency, when efficiency is defined as “lower energy consumption for a given speed.”

It has, however, always been a function of increased power output.

Before going into the science of it, let’s discuss how this makes sense from a logical perspective. Time has alwasy been the primary form of currency. A powerful runner can finish a race and begin recovery much more quickly than a slower runner. This frees the powerful runner from the effects of the race much more quickly, and reduces the time that it takes for this person to engage fully with a new task, relative to a less powerful runner traveling the same distance.

The benefits of this are as obvious as they are many, whether we be talking evolutionarily, or in terms of the body’s economy. This also holds when you look at how we define performance across all sports: increased power (and not increased efficiency) begets greater performance. Whether it be during a running race or a baseball game, whoever can apply the most energy effectively in the shortest amount of time towards achieving the goal will come out on top.

(I’ll discuss the deeper implications of this sentence in another post.)

The science corroborates this theory. In Running Science, Owen Anderson is quite clear: “The marathon is a power race.” He discusses at length how the idea of doing long, slow training for what is (presumably) a long, slow race is superficially logical but ultimately flawed. While developing aerobic capacity is immeasurably important for the marathon, as speeds get faster, greater power becomes more and more important.

The importance of power holds even for the ultramarathon. Numerous studies have been done confirming the idea that phyisological indicators of power maximums—peak treadmill velocity and VO2 MAX—correlate strongly with ultramarathon performance.

The sports technique (whether it be running technique, golf technique, swimming technique, etc.) that lends itself to the development of greater power, and not increased efficiency, can be judged to be “better,” given that what makes us universally better at sports is the application of greater power. As this article finds, more runners rise onto their forefoot the faster they go. Landing on the hindfoot is reserved for the slower crowd.

But there may be other, more insidious problems with seeking efficiency in lieu of (or at the cost of) power. In my last article I wrote how, if increasing efficiency is our primary goal, at some point we are going to be sacrificing power—basically engineering our own performance losses.

It’s fine with me that some people genuinely don’t want to seek greater performance, and rather run (or do other sports) for maintenance, rather than increase, of fitness. But this discussion of performance brings up a series of questions that I believe are legitimate: is heel-striking a “running style,” or is it a biomechanical feature—a hallmark—of subcompetitive fitness? Are heel-strikers slower, or does heel-striking make the runner slower (or alternately, become a barrier to improvement)?

I believe that this discussion merits an extensive inquiry into why heel-striking is the form of choice across a majority of runners. Is this the case because more efficient is better? Or is it the case that a majority of runners are lacking in the aerobic, muscular, or metabolic power necessary to sustain a more costly technique—one which constitutes the gateway to greater athletic performance?

These are not rhetorical questions, and they are certainly not answers. However, we treat the literature’s findings in regard to efficiency as if it somehow settles the footstrike debate (or lends evidence either way). It’s time to open the discussion again, and do so by asking questions that are more relevant than efficiency to the human body’s design, as they are to its athletic performance.

Biomechanic Issues, Defining our Terms

Descriptive vs. prescriptive in running.

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When I read articles about running, I often come across phrases like “no single foot-strike pattern is representative of the entire running population.” True enough, but it doesn’t really help runners: all it does is describe the present state of affairs of the running population.

The problem that I see with this is that many people—many scientists, even—take this descriptive observation about the world and turn it into a prescriptive one. Within their statement is a hidden interpretation (shown in italics):

 “No single foot-strike pattern is representative of the entire running population. Therefore, no single foot-strike pattern should be adopted as a baseline gait for a human population.”

Why is this problematic? Let me give you another example—one that we’re all comfortable with.

Let’s suppose that we did the very same research, only about how people lift heavy objects. Statistically, our findings would be similar to running; as researchers, we’d be prompted to say: “no single lifting pattern is representative of the entire human population.” In other words, we’d make our analysis, and see that some people lift objects by bending at the waist, and others lift objects by bending at the hips.

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The difference, of course, between running and lifting heavy objects is that we have a clinical standard for lifting. We know that bending from the waist is a bad idea for virtually any human out there. There are only three options for lifting objects, and when you really think about it, there’s only one:

  1. Bend from the waist to lift a heavy object and get injured
  2. Bend from the waist and only pick up light objects without injury
  3. Bend from the hips (correctly) to lift heavy/light objects without injury

In light of this knowledge, let’s review the following statement: “no single lifting pattern is representative of the entire human population. Therefore, no single lifting pattern should be habitually adopted as a baseline lifting pattern for a human population.” This statement seems ridiculous, and kind of insistently missing the point.

But we should keep in mind that the reason it seems ridiculous is because we have a clinical standard for lifting heavy objects, namely, to minimize trunk flexion throughout the lifting action.

This, of course, doesn’t mean that midfoot/forefoot striking is better than rearfoot-striking (although it certainly sets me up to make that argument).  What it does mean is that descriptive observations about a population’s habits tell us very little about what that population should be doing. They only tell us much about what it is doing. And what we do know is that given the stratospheric injury rates for runners, the running population is doing something wrong.

We need a clinical standard for running. In order to get one, the first step is to stop interpreting descriptive statements as if they were prescriptive ones.

UPDATE: Here are a couple of good articles on how foot-strike could be a function of running speed. This all adds to the question: what should the clinical standard be—which part of our foot lands first? Probably not. But we need a standard. There are a few ideas out there, but I’ll leave that for another post.

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.

Linguistic Traps

Systemic paradigms and their repercussions: the athletic phenomenon of “heel-striking,” and its origins in scientific reductionism.

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It would be misleading to say that the philosophical currents that drive society affect our behavior and influence events. It’s much more accurate to say that those philosophical currents largely determine our patterns of behavior and generate those events.

The widespread and damaging athletic phenomenon of heel-striking is no exception.

(By “heel-striking” I refer to the global set of gait characteristics which results in the runner putting their weight on the heel of the landing foot ahead of the center of mass).

Systems thinking proposes that our “mental models”—our belief systems about the world—create the very fabric of society, and therefore the patterns of behavior that emerge. The repercussions that our worldview has on our thought, our social structure, and our lives, are vast, and they are powerful.

Continue reading Systemic paradigms and their repercussions: the athletic phenomenon of “heel-striking,” and its origins in scientific reductionism. →