Tag Archives: Running

Biomechanic Issues, Thinking in Systems

Gravity: The dilemma of the “slow runner.”

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Some of us just want to run slowly. We don’t really want to get fast—we just don’t care.

That’s okay. We’re all entitled to our own ways of running. But while we do that, we should recognize that there are some ways of running that observe the realities of the world (and some that don’t). Someone I met once said:

All models are wrong, and some are useful.

That goes for any and all of our ideas, including our body’s idea of what is the best way to run. No idea will ever be able to exactly model the world. But some are more useful than others—and the useful ones are useful because they account for such realities with a certain success.

We must stand in observation of the reality that, when we run, the most important force we will interact with is The Force of Gravity. The quality of our interactions with gravity will determine whether we become injured or not (among other things, like speed).

In systems thinking terms, we move and live within a particular physical system. Inside of that system, there are certain constant and variable forces which the body must be capable of interacting with. If it isn’t (yet) capable of interacting with those forces, and we push it to do so, we will compromise its integrity.

In that system, if we push off the ground, we will accelerate back to it at a rate of 9.78m/s² (32ft/s²). Which means two very important things: first, that the longer we are suspended in the air, the more we will accelerate. Second, in order to maintain bodily integrity, our muscles (but also our bones and connective tissue) must be strong enough to resist the stresses incurred by interacting with that magic number.

What this amounts to in athletic terms is that body must have (1) very strong muscles, capable of responding explosively in sustained activity, and (2), the ability to maintain the center of mass (the torso) relatively stable throughout the run. In other words, it must have the ability to make the torso rise and fall as little as possible. 

How does the body achieve this mechanically?

By moving the legs faster, i.e. increasing the stride rate (to somewhere around 180 steps per minute). If we can make our feet strike the ground 20 milliseconds (.02 seconds) faster than before, that would be .02 seconds less that we’d be accelerating towards the ground. Stronger and more powerful muscles (to move our legs faster) mean that we’re accelerating less towards the ground. But here’s the kicker:

It also means that they are more capable of withstanding the stress placed on them by gravity.

But wait: there’s more!

As Owen Anderson writes in Running Science, if we could make a 20 millisecond (ms) improvement between footfalls, that would constitute a time improvement of 756 seconds across the duration of a marathon—in other words, an improvement of 12 minutes and 36 seconds! As Anderson himself writes:

[That is] an almost infinitesimal change and therefore one that most runners can easily make.

In the interest of beating this point into the ground (pun intended), that’s 12 minutes and 36 seconds we’re not accelerating towards the ground. And remember the thing about acceleration: the first 20 milliseconds and the last 20 are not created equal.

If we’re running at 150 steps per minute, we might be in the air for 60% of the gait cycle. Doing the calculations for you, we’re accelerating towards the ground for 116 ms.

At the end of the first 20 ms of acceleration, we’d be going at a speed of .09 m/s second (.29 f/s).

At the end of the 116 ms of acceleration, we’d be going at .056 m/s, or 1.64 f/s.

But if we make a 20 ms improvement from 116 (in other words, 96), our maximum falling speed would be of 0.47 m/s, or 1.54 f/s.

Let’s reiterate: A 20 ms improvement from 116 ms means that the runner is going a tenth of a foot per second slower upon hitting the ground, and it’s only that way because of muscles that are stronger.

If take the time and energy to make our bodies more capable of interacting with gravity, we will inevitably end up being the faster version of ourselves.

Let’s internalize this, because it really does constitute the minimum passing grade of the “entry exam” for a runner:

Being strong enough to interact with gravity is the minimum power requirement for a human runner.

Although elite runners have muscles that are much more powerful than necessary to deal with the requisite 9.8 m/s², that number is where the laws of physics and the Earth’s mass have set the bar for human runners. That is our system. Those are its requirements. Let’s stand in observation of that fact.

There are two good ways that I know of, that can get us to meet those requirements. The first is by jumping rope as I’ve described, and the second one is an exercise in this video by Dr. Mark Cucuzella (at 6:09).

(By all means, look at the entire video—it’s very engaging and informative).

Now, go talk to gravity until you’ve gotten to know it like an old friend.

UPDATE: You can find a couple of good discussions on stride rate and running speed here and here.

Thinking in Systems

“Shifting the burden” in running.

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Shifting the burden is a systems thinking notion that refers to a tendency to shift responsibility for the functioning of the system onto external factors. Take crutches as an example. When we use crutches, we shift the burden of keeping us in balance away from our inner ear, the calculations of our cerebellum (located at the base of the brain), and the resulting activity of the muscles that work to keep us upright. They no longer need to bear the burden of balance. Now the burden is on the crutches.

For now, let’s put aside the fact that some people need to use crutches to move around in the world. Instead, lets focus on what would happen if a fully able-bodied person begins to use crutches: they would begin to lose the back strength necessary to balance their own bodies.

There are many examples of this phenomenon. Most of us are aware that astronauts experience bone and muscle deterioration while in space, to such an extent that it becomes vital for them to maintain a rigorous exercise routine during missions. A much less extreme example of this is when we put our arm in a cast to heal a broken bone: after two months of immobility, that arm will be much thinner and weaker than the other.

In both cases, the burden of support was shifted away from the muscles and bones, and they grew correspondingly weaker.

“Shifting the burden” is relevant to running because as a society, we have largely shifted the burden of developing speed away from the body and onto the sports drinks and shoe industry.

But that industry helps a lot of people get started! There would be many people that wouldn’t be able to run marathons if not for big-heeled running shoes and energy gels!

That’s the problem. Big-heeled running shoes is a quick-fix. Imagine how much longer it would take to go through the trouble of making a comprehensive mechanical assesment of the body, and taking the time to develop all the correct muscular systems. Just put motion-control shoes on someone, and you can get them running now!

Let me share a little nugget of wisdom from The Fifth Discipline, one of the most important works of Systems Thinking. Peter Senge writes:

“An underlying problem generates symptoms that demand attention. But the underlying problem is difficult for people to address, either because it is obscure or costly to confront. So people “shift the burden” of their problems to other solutions—well-intentioned, easy solutions which seem extremely efficient. Unfortunately, the easier “solutions” only ameliorate the symptoms; they leave the underlying problem unaltered. The underlying problem grows worse, unnoticed because the symptoms apparently clear up, and the system loses whatever abilities it had to solve the underlying problem.”

Fixing the body’s biomechanics and making sure everything is in tip-top shape and ready to run a 5k or a marathon is both obscure and costly to confront (in time, energy, and vision, if not money). Once the underlying problem of shifting the burden (say, to running shoes with a big heel) has grown bad enough, we experience a breakdown in the system’s capabilities: injury.

“Shifting the burden” occurs all over, and not just in physical systems: people shift the burden of interacting socially away from their abilities and from managing their anxiety onto alcohol, for example. You add a little bit of alcohol, and the tongue loosens. But begin to depend on it too much, and eventually it’ll begin to negatively affect your social interactions—making the very problem that you were trying to solve grow even worse.

This discussion illustrates the reason why I use systems thinking to develop my training routines. As long as the thing that we’re trying to develop is some kind of system, the principle of “shifting the burden” will hold. In other words, it doesn’t matter what kind of system we’re talking about. If the burden of its performance gets shifted onto another system, it will become dependent on that other system.

By coming to the conversation armed with systems thinking, we can neatly sidestep the discussions of whether soft shoes are better than minimalist shoes (or whatever). If what we’re doing is an example of shifting the burden, the system is going to head towards dependency and an eventual inability to perform. It doesn’t matter if we’re talking about the economic system, the psychological system, or the musculoskeletal system. No matter what the doctor tells you:

“Any long-term solution must strengthen the ability of the system to shoulder its own burdens” – Donella Meadows, Thinking in Systems: A primer.

It’s a sad story for those maximalists pushing their Hoka Ones like happy candy: soft shoes with big heels are an excellent example of shifting the burden. For example, it has been argued that heeled shoes allow the leg to strike the body ahead of the center of mass (i.e. the torso). This shifts the burden of increasing the length of the stride away from the quads and the glutes on the pushoff (rear) leg and away from the flexors on the swing (front) leg.

Because now the stride can be longer despite weaker muscles, running will now incurring massive stress damage to the body. (For a longer discussion on this point, see this post.

We don’t have wait for the debate between minimalists and maximalists to settle in order to decide whether shoes with a big heel-toe drop is good for us or not. That’s not the point. All we have to ask is: are we shifting the burden of [blank] away from [blank]?

In future posts, I’ll write extensively about many of the ways in which we shift the burden, and how to shift it back to our biomechanics and physiology. For now, we can begin that general process by thinking about a quote from Bruce Lee:

“It’s not the daily increase but the daily decrease. Hack away at the unessential.”

This isn’t just a cute tidbit of wisdom. As I’ve discussed before, the ways in which we think about things affect our biomechanics. The reason Bruce Lee’s speed and power was unequaled was probably because of the unequaled discipline and creativity with which he maintained an evolving understanding of such philosophical statements.

Like Bruce Lee, find those systems we shift the burden towards. Through trial and error, lets hack away at them.