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Runners are often told that strength training is integral to improving running speed and running economy. But there might be a little bit of a problem with this advice. I recently posted about a body of research that pointed to the idea that, for a variety of biomechanical reasons, weaker muscles in a trained runner correlated with a greater running economy (specifically at the calf region). The consensus was that running economy increased with achilles tendon loading, and decreased with calf muscle (gastrocnemius and soleus) activity.

More muscle means worse economy. A recent article in Runner’s World confirmed this, citing a study that found that running economy was related to the balance of strength between the anterior and posterior muscles (specifically, the quads and hamstrings). It was not, as most of us suspect, a function of pure muscle strength—overall, competent runners had weaker muscles than novice runners.

This brings up several questions. The first is, of course, how can weaker muscles make you run faster? The answer, I believe, is systemic, and our ability to find it hinges on what we mean by “strength training”—and how usefully we’ve defined it for ourselves. In the most basic terms, the strength of an individual muscle has little to no bearing on how the hip-leg-foot mechanical system will function in practice.

The power of this system—when power refers to how much force the leg can put out per unit of time—is much more a function of how well the parts move together, than how strong any individual part (or indeed, all of its parts) are individually. Someone endowed with extremely strong muscles that are all just slightly out of sync will have a completely rigid leg, not a powerful one.

It’s necessary, therefore, to make sure we all mean the same thing by “strength training.” Strictly speaking, the kind of explosive power (plyometric) training that a lot of runners do, which actually does develop hip and leg power, is “strength training”—but of the entire system. We need to be clear on what we mean by this to know if strength training will actually help us become better runners. Do we mean pure strength, or explosive strength?

The second question is more related to a practical matter, and is a consequence of answering the first. What are our reasons to train pure “muscle strength” in the first place? We’d better have them, given the above evidence that muscle strength correlates with low running economy. If we do prescribe a strength training program to runners, are we potentially hurting their running economy?

I don’t have an answer for this. Most of my training is either isometric or plyometric, and the few strength exercises that I do—such as barbell squats—are for balancing my body out, more than anything.

The third question is a matter of causality: why did the novice runners in the Runner’s World article have stronger muscles? To speculate about this, we have to return to the body of research mentioned above. The reason that weaker muscles correlated with greater running economy has to do with the biomechanics of particular bodies. One of the abovementioned studies looked at the ankle region of highly-trained runners, and found that runners who had longer heels (meaning a greater distance between the ankle and the heel) had poorer running economy and greater muscle power.

None of this is surprising, once you think about it. When the hip-leg-foot system pushes against the ground, it exerts force directly into the ground, at a perpendicular angle. To achieve this, the foot works a lot like a lever: the achilles tendon is connected to the end of the lever arm (the heel bone). When it shortens, the heel raises, meaning that the foot rotates downwards around the ankle—the fulcrum—allowing force to be exerted into the ground. Because every action has an equal and opposite reaction, force also travels in the exact opposite direction: into the calf, parallel to the calf bones.


Because of the properties of the muscle-tendon system, this results in a trade-off. If you increase the length of the lever arm—the distance from the ankle to the heel—leverage increases, meaning that the calf muscles have an easier time pulling on the lever and causing the foot to point.

However, this also means that the tendons work more like a rope and less like a spring: The elastic fibers that make up the tendon have to be aligned with the direction of force in order to store that mechanical energy. If the lever is longer, the achilles tendon is at a greater angle to the direction of force, and therefore less capable of storing mechanical energy.

In other words: greater leverage = less energy return. When your skeletal structure compels you to use your muscles more (resulting in stronger muscles), you also have less energy return, which is a critical component of running economy.

The reason that the novice runners in the Runner’s World article have stronger muscles may have less to do with the fact that they’re untrained and more with why they’re untrained. Perhaps one of the reasons is that they are not dimensionally prediposed to train running. Supposing this is the case, you might look at their bodies and find that they are built for leverage, not for energy return.

You might. A longitudinal—long-term—study would confirm this (or not). If the untrained runners started training, would their running economy get better? According to the abovementioned study, not really—or at least not completely: the study estimated that 56% of running economy could be accounted for by heel length alone. In addition, the runners they looked at were all highly trained (and had comparable running performance) and their running economy still varied by 20-30%.

(This also means that while longer heels contribute to a lower running economy, they do not necessarily contribute to lower running performance. The human body has many faculties, each of which contribute differently to performance. Energy return is only one of them).

One thing is clear: as a collective, we need to be a lot more careful with the advice that we give runners. As I mentioned above, what does “strength training” mean, and what exactly are we recommending that runners do, if we make such a suggestion? The skeletal mechanics of the body (let alone the possible interpretations of the phrase “strength training”) means that the same advice given to two different runners can have very different ramifications—or worse yet, none at all.

Tendinopathy, musculoskeletal characteristics, systemic strategies, and running.

I came across a very interesting research article titled Running Biomechanics: Shorter Heels, Better Economy. Evidence is presented that running economy is determined by supposedly immutable factors in the athlete’s musculoskeletal structure, such as the moment arm of the achilles tendon, which refers to the distance between the achilles tendon and the ankle joint, which serves as the fulcrum of rotation. The evidence presented suggests that greater running economy—the amount of energy stored in the tendons, to be used in the next step—correlates with a shorter moment arm far more strongly than with other factors such as  lower leg volume or VO2 (a given rate of oxygen consumption). This has serious implications for the advice given to runners on how to improve their running economy.


The authors conclude that 56% of the variation in running economy between runners could be predicted by the moment arm of the achilles tendon. This is interesting, considering that other studies suggest that there are 20-30% differences in running economy even among elite athletes. The study, which selected highly-trained, competitive male runners as participants, corroborates these findings.

This body of data suggests that, by and large, training does not affect running economy, when running economy is a function of the body’s skeletal configuration. What does this mean? That when it is up to the physical characteristics of someone’s bone structure, changes to running economy cannot be easily made. Because the achilles tendon moment arm (which corresponds to the distance between the ankle joint and the heel bone) is fixed in adults, the abovementioned 56% in variation is also fixed.

However, factors that aren’t skeletal could affect running economy—factors such as poor muscle coordination and imbalance. For example, one of the most common problems in amateur runners is stiffness of the soleus and gastrocnemius (calf) muscles. Often, this contributes to excessive plantarflexion (pointing of the foot) and premature heel rise during the late stage of the stance phase of gait. (Heel rise should occur during pushoff phase).

dosiflexion_plantar_flexion (1)

By raising the heel, the achilles tendon moment arm increases, allowing the gastrocnemius to exert more force against the ground. However, as the above-referenced article would suggest, this means that comparatively less energy would be stored in the achilles tendon. Other research on achilles tendinopathy corroborates this, with findings that those who suffer from the condition often have a reduced activation of the tibialis anterior muscle. By and large, those who suffer from achilles tendinopathy will point the foot to decrease loading of the tendon.

It is likely that pointing the foot as a result of achilles tendinopathy is a two-pronged strategy: both the reduction in tendon loading and the increase in achilles moment arm contribute to maintaining a functioning system. In light of the abovementioned research, this increase in moment arm means that force exerted into the ground is achieved through active muscle contractions of the soleus and gastrocnemius, rather than passive energy storage in the achilles tendon. By offsetting the production of power from the tendon to the muscle, the limb can remain useful in a suboptimal state.

This means that there is no single way to improve running performance. In fact, unless you have severely impaired biomechanics—which, granted, is more than commonplace in modern runners—there is nothing much you can do about your running economy. But unless you already use your body perfectly, there is no point in worrying about a large achilles moment arm. And if you already do use your body perfectly, there is no point in worrying about it either: you’ll simply end up developing other faculties, such as the aerobic engine, as your body seeks to achieve greater speed and endurance.

In Running Science, Owen Anderson compares Steve Prefontaine and Frank Shorter, writing that even though both athletes had very similar times in the 10,000 meter race, Prefontaine had a markedly higher VO2max (maximum volume of oxygen consumption per minute) than Shorter.   Anderson’s analysis is that Shorter had superior biomechanics, while Prefontaine had to develop greater aerobic capacity. However, in light of the presented evidence (and a cursory glance over both athletes’ physiology and body type), it is likely that Shorter had musculoskeletal advantages over Prefontaine, such as a reduced achilles tendon moment arm.

Steve Prefontaine
                   Steve Prefontaine

Concretely, this means that faulty biomechanics aside, certain runners will benefit more from particular kinds of training than others. For example, a runner with a huge achilles tendon moment arm may benefit more from weightlifting and muscle power exercises, particularly those that develop the tibialis anterior, allowing for ankle stabilization during the landing phase at greater ankle dorsiflexion than runners with a smaller achilles tendon moment arm: as mentioned above, dorsiflexing the foot reduces the achilles moment arm and increases loading (which is why those with achilles tendinopathy avoid it).

Runners who have to increase dorsiflexion to a greater extent for a given running economy will still be relying on more muscle power than those who don’t, at least in some fashion: the moment arm of the tibialis anterior (which dorsiflexes the foot) increases throughout dorsiflexion. In other words, this will offset the need for muscle power from the rear muscles to the front muscles, at least in the calf region.

It’s likely that the same biomechanic advice—advice on how to develop running economy—won’t be equally useful for two different runners. Although running economy will be largely a function of achilles tendon moment arm, running speed, endurance, and overall performance is not. Runners should study their bodies (or get studied by an expert) to see what kinds of training will help them develop their race performance.

Keep in mind that running economy is not the same thing as running performance. Prefontaine and Shorter’s comparison should tell you that. However, certain people have attributes that favor specific skillsets. Some people have great muscle power, others have great economy. Lately, running trends have been focusing too much on the energy-return properties of the body—so much so that runners are either alienated or forget that the body has other properties. The body is always more complex than the latest trend says so. And even if the latest trend does not validate the attributes that we should develop to make us better runners, it doesn’t mean those attributes aren’t there, or are somehow less important. The human body is an extremely complex machine, capable of achieving great performance through many different avenues. With a bit of study, we can figure out what those are.

A great, great article on reactive sports rehab: the “foam roller” paradox.

A great article by Robert Camacho, titled Your IT Band is Not the Enemy (But Maybe Your Foam Roller Is), neatly summarizes one of the many shifting-the-burden systems that we encounter in mainstream sports rehab: the use of the foam roller. When we apply the foam roller to our IT bands, it alleviates pain, and allows (most of) us to forget that the ultimate solution to the problem is actually resolving muscle imbalances.

The article neatly points out that by not resolving those imbalances,

you aren’t really doing anything to affect any kind of permanent change and in some cases you may be pushing the issue further.

The issue here is that the two muscles that are most directly connected to IT band function, the tensor fasciae latae and the gluteus medius, aren’t being developed properly, and aren’t being taught to interact with the rest of the hip musculature. As mentioned above, this is an excellent example of a shifting the burden system, which is characterized by how the “symptomatic,” short-term solution itself reduces the ability of the system to solve the fundamental problem:

The problem with this is that you’re now statically using a structure to achieve dynamic stabilization. That’s kind of like responding to the shocks on your car being too loose by tightening them up so much that they can’t move.

In systems thinking terms, this is known as a loss of resilience. By tightening up like this, the leg cannot adapt to changing conditions, such as variations in terrain, and the progression of muscle fatigue. In other words, this is a guaranteed recipe for constant, chronic injury.

The one caveat that I would add to the article’s message (although it is far from a counterargument) is that the foam roller may be a useful tool while also engaging in rehab that solves the fundamental problem. Because the foam roller does loosen up the muscles, when the hip is too tight to move well, the foam roller can be used before doing the relevant hip workouts, in order to make them more effective. As with other shifting the burden systems such as anaphylaxis, (which I discuss halfway through this article) sometimes you need the symptomatic solution to keep the system afloat, but only while diligently implementing the fundamental solution to solve the underlying problem.

A culture of injury

The endurance running hypothesis submits that humans evolved as desert persistence hunters—fast, long-distance running machines. Contemporary research has found no relationship between running and knee osteoarthritis. And the Tarahumara—the Mexican tribe of running people also known as rarámurihabitually run hundreds of miles per week while sustaining only a modicum of injuries. All of this raises the following question:

Why do we continue to insist that running is bad for the knees?

The most immediate answer is that, for a critical mass of westerners, running has actually created a variety of musculoskeletal and metabolic problems, enough so that it’s gotten a bad rap. However, especially in light of the above data, this doesn’t mean that running is bad. What it does mean is that we’re doing something fundamentally wrong.

Like most systemic problems, it has more than one source. Consider this: not only do we run in biomechanically disadvantageous ways, but we’ve done that for so long that the cultural consciousness has internalized this as the notion that running is somehow inherently injurious. Once this idea has been internalized, we lose any incentive, and any reason, to change incorrect patterns of motion. Because we’ve operated for so long under this conclusion, chronic injury and dysfunction becomes not only the standard, but also the norm.

However, it does more than that: chronic injury becomes the badge of the runner—a badge worn with pride. It is at this point that the culture of injury becomes fully cemented. If you aren’t injured, you’re not a “real” runner; you don’t share the burdens that we all share. You don’t go through the constant rite of passage that we all go through. You’re an anomaly, an exception. You’re special. Good for you.

With most runners, injury is the way of the world. Injury is a self-fulfilling prophecy that has everyone singing its virtues. If you aren’t injured yet, you keep training. It’s almost as if you look for injury. Why? Well, because if running is inherently injurious, if you’re not injured, you’re not doing it right. If you don’t have to constantly stretch and rehabilitate and ice and elevate, maybe it’s time to train a little harder.

So, what do we have here? A self-fulfilling prophecy, one which for the majority usually removes the possibility of running completely pain and injury free. The world in which we don’t have to RICE it up all the time, and foam roll our IT band isn’t one we’re used to considering.

Think that this world is a fantasy? Return to the evidence above. You’ll likely find that your skepticism is far more a function of the story we’ve been telling ourselves (and the socio-athletic system that’s emerged from it) than a function of the actual capabilities of your particular human body.

The first step to change this feedback loop is not, of course, to just go out and try to run like the rarámuri. That would be silly. Mere wishful thinking cannot ever replace good biomechanics and great training volume over the course of a lifetime, not to mention the benefits of being steeped in a culture of running. Most of us don’t have that, and never will.

But what we could do is to believe that it can somehow be different. We can believe that, given the evidence above, it makes sense to try and create the world in which we’re not plagued by injury, and beset by the notion that it is somehow an inevitability. Once we believe that, we can realize how antiquated the notion of “pushing through the pain” actually is.

If the plantar fascia begins to hurt, why not change something in our stride so that it stops? Change what? Go figure it out. But the injury is not inevitable. Only the notion of pushing through it—that useless phrase that our athletic culture has given us—makes it a certainty.