Tag Archives: efficiency

Biomechanic Issues

What is the role of efficiency in athletic performance?

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In various social media, the following observation was made several times about my last post: efficiency plays an important role in athletic performance.

Yes. Efficiency is an essential indicator of athletic performance. However, all efficiencies must be in service of greater power production, not simply sought after without a good reason: efficiency has no real benefit when divorced from other variables.

Here’s a quick but illustrative example: It takes a lot more energy to keep a spine straight, with hips, head, and shoulders evenly stacked, than it does to let that spine develop a pronounced thoracic kyphosis—the spine and shoulder curvature we associate with “bad posture.” Does this consume less energy? Yes. But in doing so, it puts a variety of systems—not just muscles, but even the respiratory system—at a disadvantage.

(Tellingly enough, there’s an important relationship between metabolic and aerobic power and the capability to maintain an upright posture).

Achilles_Statue_in_Corfu_by_MaJr12
Good Posture, brought to you by Achilleus

If we try doing a front squat with bad posture, we’ll set ourselves up for either a plateau or an injury. In effect, we have to resolve this problem by increasing the body’s energy consumption (reducing efficiency) in order to produce the alignment that allows us to correctly perform this movement under load.

Ultimately, however, efficiency is extremely important in sports such as running. This is known as running economy. Elite runners tend to have great running economy, meaning that they use less energy to cover a certain distance.

There are a few ways that running economy can be improved: one is to increase aerobic power. Six times as much energy can be gotten from molecules of glucose that are burned aerobically rather than anaerobically.

Another way is to increase neuromuscular synchronization and power. A knee that collapses in or hip that collapses up during the running stride is known as a “power leak,” meaning that muscles are misaligned and therefore pushing the body up, laterally, or rotationally instead of contributing to driving it forward.

Yet another way to increase running economy is to become smaller. This includes having reduced fat percentage and increased muscle percentage, but it encompasses more than that: runners that are volumetrically smaller have a much easier time traveling distance than runners that are volumetrically larger. Why? If you’re taller, not only will your bones and muscles have to be thicker (in order to retain the same proportions), but then your organs, especially your heart and circulatory system, will be working that much more to pump blood from your toes to your brain.

It doesn’t matter what aspect of running economy you’re talking about. Not only does the economical runner expend less total energy than the non-economical runner, but a greater percentage of total energy expenditure ends up going towards crossing the finish line rather than being lost in vertical, lateral, or torsional oscillation, power leaks, or greater metabolic upkeep.

The question of efficiency or running economy should always be asked in tandem with the question of athletic performance: is seeking some initial efficiency—for example, bowing my upper back because I’m tired—going to hinder my athletic performance or development?

Personally, I believe that “good form” for any athletic activity is “that form which allows us to express greater athletic power.” That’s how it’s defined across martial arts, baseball, the decathlon, and marbles. That should be how we define it in running too.

When a forefoot strike results from all the correct physiological and gait factors, a greater proportion of the stance will be spent on the forefoot, meaning that a greater proportion of the stance phase will go into force production. The stance is shorter overall, and the speed is faster. Is this stride type more costly (and does it produce its own set of injuries)? Maybe, possibly. Sure.

Do certain distances place such a burden on people’s endurance—even that of elite athletes—that they opt out of the “power producing” stride type completely? That’s the billion-dollar question, and given the answer, we might find that it is completely within reason to adopt a hybrid stride or even a heel strike at certain distances, full stop. (Or, you know, we could just walk).

Great form (and great technique) are expenses of energy, both immediate and in terms of time and training. But achieving them will facilitate efficiency at a higher athletic level: we’ll expend more energy, but we’ll be able to apply a greater percentage of that energy towards the achievement of our athletic goals.

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

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.