The popularity of the trend of minimalist (zero-drop, low-cushioning) shoes has coincided with a sharp increase in running injuries, according to some sources. This has caused a large amount of community, media, and legal blowback on minimalist shoes, the most salient of which is the recent class-action lawsuit against Vibram, for misleading advertisement.
Misleading advertisement should always be punished. Vibram peddled their five-fingers shoes as the solution to running injuries. They are not. They should never have been advertised that way.
But this blowback has created an unfortunate tendency: blaming the minimalist shoes themselves as the cause of injury.
They aren’t the cause. Although this may seem contradictory, it is the fact that so many people get injured when switching from “maximalist” (shoes that are highly-cushioned; often with an elevated heel) to minimalist shoes—but not vice versa—that suggests that minimalist shoes are better for the biomechanics of human running.
This apparent contradiction can be resolved—but in order to do that we must look at the issue from a systems thinking perspective. And for that, we have to begin with the concept of “resilience.”
In Thinking in Systems: A primer, Donella Meadows writes that one of the most important characteristics of any system is resilience—“the ability to bounce or spring back into shape, position, etc. after being pressed or stretched.” According to her, one of the key causes of resilience in any system is richness of structure and dynamism of process. If the system’s parts are in constant motion and conversation, and no individual part is left out of play, the system will be highly resilient.
However, maximalist shoes, particularly those with a heel-toe drop, compromise the resiliency of the foot, as a muscular, skeletal, and neurological system. Why? Because one of the things that raising the heel of the shoe accomplishes is that it becomes less painful to overstride and “heel-strike”—land on the ground heel-first, ahead of the center of mass. Mechanically speaking, this means that a heel-striker doesn’t need to use their hip flexors (the muscles that let you raise the thigh to the chest) as much as a midfoot-striker does, to extend their stride forwards the same distance. Specifically, this causes the hip flexors in many heel-strikers to be too tight, and therefore largely immobile.
Furthermore, maximalist shoes are designed to be comfortable (according to followers of the Hoka One One phenomenon). Well, two of the key elements of comfort are constancy and safety. On this topic, Mrs. Meadows cites ecologist C.S. Hollins, who writes:
“Placing a system in a straitjacket of constancy can cause fragility to evolve.”
Systems thinkers refer to this phenomenon as a “shifting the burden” system.
As I’ve discussed before, a shifting the burden system begins when there is a problem that needs to be solved. In this case, runners want to solve the problem of extending the stride some distance X. And to solve that problem, there is a quick-and-easy “solution:” slap a cushioned heel on the shoe and extend the leg forwards. But this “solution”—called the “symptomatic solution”—has a side-effect: by allowing the hip flexors to remain passive during the stride while the hip extensors (hamstrings, glutes, and calves) are relatively overactive, the system’s resilience is slowly being compromised: these two muscle groups are “unlearning” how to cooperate with each other to move the body.
However, the problem of lengthening the stride does have a real solution—called the “fundamental” solution. The fundamental solution is to increase hip flexor strength and mobility, so that by gaining hip flexion, the leg can then extend comparatively further and more powerfully. As The Gait Guys often say:
“Develop anterior (flexor) strength to achieve posterior (extensor) length.”
In other words, the ability to extend the leg and exert power on the ground is centered on this flexor-extensor communication. You can see how the biomechanic principle coincides with the systemic principle: increase the amount of parts that are moving and in active conversation and you’ll increase the resiliency of the system.
However, this means that putting a heel on the shoe is a huge problem: the more time you have a heel on the shoe, the more difficult it is to try and get the hip flexors to start working again. As Peter Senge writes in The Fifth Discipline:
“The side effects of the symptomatic solution make it still harder to apply the fundamental solution. Over time, people rely more and more on the symptomatic solution, which seemingly becomes the only solution.”
In systems thinking parlance, the diagram for this shifting the burden system can be drawn as follows:
When the foot (and the rest of the body)—whose resilience has been compromised and now relies on the symptomatic solution (maximalist shoes)—is exposed to the abrupt change of going into minimalist footwear, it cannot cope and becomes shocked, i.e. injured.
But the inverse—going from minimalist to maximalist footwear—isn’t equally injurious: when you have a similar human body that has never shifted the “burden” of lengthening the stride from the hip flexors to the shoes, all of its muscles have been trained to communicate with each other over the course of the years, and are so strongly coupled that body is extremely resilient. Donella Meadows writes that one of the hallmarks of resilience is redundancy—allowing one mechanism can kick in if another fails.
This is exactly what we see in elite athletes who ran barefoot and in minimalist footwear for the majority of their childhood and adolescence. When that highly redundant, highly resilient athlete is given a maximalist shoe, their body has a much easier time adapting to the change.
When you have a population (athletes that ran in minimalist shoes during their childhood and adolescence) that has a certain characteristic (a low incidence of injury), and you make an abrupt change in the system (switching to maximalist shoes), if the system doesn’t show erratic behavior (recurring injury), you can be reasonably certain that the previous conditions of the system (running in minimalist shoes) contributed to its resilience.
That inference becomes even stronger when you look at the rest of the evidence: if the system begins to show erratic behavior when subjected to a change, you can be reasonably certain that there was something about the previous conditions that were contributing to the fragility of the system. In other words, when you look at the fact that runners get injured when switching from maximalist to minimalist shoes but much less so when switching from minimalist to maximalist shoes, you can be reasonably certain that it is maximalist shoes, and not minimalist shoes, that were the primary contributors to injury.
So why is this surprising? Donella Meadows suggests that it is because most of us have linear minds, yet we live in a non-linear world. In other words, when we see somebody go from a maximalist to a minimalist shoe, and they get hurt, we draw the closest line between the two points and say, “it must’ve been the shoe.” But that kind of thinking won’t get us very far; we need to think in systems in order to understand why the apparently contradictory answer, in the case of running injuries, is the right one. Mrs. Meadows writes:
“Non-linearities are important … because they confound our expectations about the relationship between action and response. They can flip a system from one mode of behavior to another.”
To a systems thinker, it is unsurprising that this “contradictory” answer is surprising to us. The fact remains that many of us want a simple answer. We’d like to think that shorthand, sound bites, and headlines can give us all of the information that we really need. But that’s the kind of thinking that led to the naive adoption of both maximalist and minimalist shoes—and the subsequent injuries. Our bodies are immensely complex systems, which behave in a chaotic fashion. Linear thinking is only going to get us so far, in trying to explain and understand their behavior. When the prevailing winds of society encourage us to jump on or off a bandwagon, it behooves us to step back and look at things from a systemic perspective.
Sometimes, the simplest explanation is no explanation at all. Let’s not turn Occam’s razor on ourselves. We’re going to get cut.