Tag Archives: running gait

Biomechanic Issues, Uncategorized

The Running Gait, Part 1: Contralaterality

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All gait is a contralateral movement. Although It seems like the most obvious statement (perhaps to the point of being boring), it often astonishes me just how unexamined it remains. Discussing both the theoretical and practical implications—what it means for our training—is what this series of posts is all about.

To say that a movement is contralateral is to say that when something happens in one side, the opposite will happen in the other side. During gait, if our left leg moves forward, our right leg moves back. But our gait is also reciprocal, meaning that the limbs in the same side move in opposition to each other, to balance their movement. If our right leg, supporting our body during the stance phase of gait, moves back, our right arm swings forward in a passive motion meant to balance out this movement.

This kind of reciprocal action is very similar to the kind of activity that you find in a lot of modern machines. Let’s take the internal combustion engine as an example. To make this simple, let’s look at a flat twin engine like the one mounted on a lot of BMW motorcycles:

Boxerengineanimation

In the image you can see two pistons, each moving in opposition to each other around a crankshaft. This movement is—or should be—a lot like the movement of the legs around the hips. By the way, this imagery isn’t just a metaphor: there are important similarities between the mechanics of the piston system and the mechanics of the hips and legs.

I liken the lowest point in the piston’s rotation to when the leg (the right) is in swing (1). The apex of the piston’s upswing corresponds to midstance, where one leg (the right) is fully supporting the body (2). At the same moment, an opposing piston must be in the lowest point of its downswing in order to balance the mechanism.

Piston Mo
By Zephyris – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10896588

Any problems in the balance of the pistons or the crankshaft can cause something to go horribly wrong. The same goes for the body, in order for its movement to be in balance. As the left leg clears the ground behind the body, the right (opposite) arm must be ready to initiate the upswing. And the right leg should be ready to start reaching for the ground below.

Insofar this is the case, the movement can be said to be contralateral.

Let’s look at the pictures of Mo again (taken as he is sprinting down the final stretch of his gold-medal performance in the 10,000 meter event of the 2012 Olympics). As you can see from the right arm in (1) and the left arm in (2), both pictures are taken at the same moment in gait (from the frame of reference of the arms).

MO Mo

By comparing both pictures you can see a bit more flexion in early stance for the left leg (1), than for the right leg (2). At this moment in gait, the right leg trails further behind the body (1) than the left leg. (The left calf (1) is also at a larger angle than the right (2).) Without getting too far into the mechanical details, it would seem that Mo’s having a little bit more trouble stepping forward with the right leg than with the left.

In effect, in picture (1) his left leg is flexed because it’s waiting for the trailing right leg to catch up. And if you look at the orientation of his forearms, you can see that the right elbow (1) is far more flexed than the left (2), mimicking, to almost a perfect degree, the angle of the opposite knee in each of the pictures.

The point is that it wouldn’t matter where you look at the piston system (of an internal combustion engine) from. Whether you observe the piston system from the frame of reference of the piston head, the main axis of the crankshaft, or the counterweights, you would see that the entire system is balanced. Each counterweight remains perfectly opposite to a piston, and the pistons remain perfectly opposite to each other.

This is so important that much of what makes sports cars—particularly “traditional” sports cars like Ferraris—and race cars cost as much as they do is the technology to keep the engine block balanced to the picogram. The better this is accomplished, the more torque can go through the engine without breaking apart the block.

Mo Farah is not some amateur. For the past few years, he has set the highwater mark for excellence in distance running up to the 10,000 meters. And even then there are differences.

Why is this happening? The “big” answer to this question probably isn’t in some esoteric discussion of biomechanics. Quite simply, the 10,000 meters are run on an oval track, and this is the final stretch. For more than 24 laps, he’s been turning into his left leg. It’s probably a lot more tired than his right, so it’s having a harder time supporting his body during stance. (Hence the flexion).

If we asked Mo to keep running for a few more laps (not that he would) we’d find that his right leg would continue to trail a little more, and his left leg would flex even further. If you look at the video you’ll see that even down the final stretch he’s compensating quite well by driving forward with his right shoulder every step.

But as he becomes more tired, we’d see that this strategic compensation stops being enough. We’d probably observe his left foot taking increasingly longer to leave the pronation (flattening) that occurs during the stance phase. The supination (pointing) which occurs towards the end of the stance phase, would come too little, too late, possibly creating a heel whip for the duration of the race.

pronation & supination.png
Pronation and Supination

As this is happening, the huge amount of forces that go into his body as his feet strike the ground will travel through it at increasingly odd angles. There is a potent compounding effect here: The more experienced, fitter, and more rested body aligns itself correctly with the forces of running. The less experienced, less fit, and tired body does not.

For the weekend warrior with the New Year’s resolution, running a marathon is biomechanically a far more hostile experience than it is for the skillful runner. Some people overpronate from the get-go. Others start with a tight hip. Over the course of 40,000 paces, this brings nothing but disaster.

Physics favors the trained runner much like the Greek Gods favored the heroes of mythology, by further increasing their already formidable advantages in battle. The skillful runner already comes into the race with stronger muscles, denser bones, a more resilient nervous system, and a more robust metabolism. As a final reward for their training efforts, the impact forces of running fall into place and work with them, not against.

 

Linguistic Traps

Runners: Let’s not confuse Efficiency with Optimization

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We should always be careful, as runners and athletes, when shopping around for new data to help us develop our craft. We should be even more careful when this data comes in a convincing format—scientific research—and alarm bells should go off when that research isn’t put in context.

Recently, I went to take the Pose Method Level 1 coaching certification, which I wrote a pretty popular review about. With this post, I want to begin diving a little deeper into the subject, starting by addressing one of the major scientific critiques towards the outcomes of minimalist running, forefoot striking, and the Pose Method: that these techniques are less efficient than heel-striking—namely, that they use more energy across the same distance.

Well, do they? Perhaps. Most likely, in fact.

However, seeking sheer reductions in energy use may be missing the point.

Let’s take a popular sport as an example: mountain biking. One of the first things you consider when buying a new mountain bike is whether you want dual suspension, or only on the front. This is a classic trade-off: the dual suspension lets you go on more rugged terrain, but it also means that less power from every stroke goes into driving the bike forward.

A dual-suspension bike is less efficient than a front suspension bike. That’s it, right? Front suspension bikes are superior. It’s a done deal.

Well, no.

Before I go on, let me be quite clear about the argument that I’m making. I’m not saying that less efficient options are better. I’m arguing that different options can’t—and shouldn’t—be judged on efficiency alone. I’ve seen it at least a few times in the running community: the studies on whether the Pose Method lowers running efficiency are presented in one stand-alone sentence, as if by itself, and without regard for the scope and depth of functions that the human body must fulfill, efficiency means something.

Efficiency alone means nothing. The questions we should ask is: what is it getting us, and what are we sacrificing by pursuing it?

Let’s go back to the mountain bike example.

Adding that rear suspension increases the capability of the bike to interact with more rugged terrain. If you land from a high jump with a dual suspension bike, you’re less likely to break the frame—or yourself.

Not a mountain bike, but I'd say that Danny MacAskill's legs count as suspension 1 and 2.
Not a mountain bike, but I’d say that Danny MacAskill’s legs count as suspension 1 and 2.

You’ll see this across all systems: increasing the dynamism of any system (which means both its capability to interact and its rate of interaction) increases its ability to interface with other complex systems (i.e. the environment). In order for this to happen, a dynamic system has to be working with sufficient moving parts, all of which take energy to function. If we just focus on cost-cutting measures—what gets me the least energy consumption, all else aside—we’re going to be undercutting that system’s optimization at some point.

That certainly seems to be the case in human locomotion, as suggested by this study (also cited above).

We’re making a very specific—and very generalizable—trade by adding a rear suspension to the mountain bike: we’re reducing its efficiency in order to optimize it to the environment.

Lowering the efficiency, however, does not immediately mean that you’re optimizing something. In fact, it’s typical to find that if optimization drops below a certain threshold, so does efficiency. A bike needs intact tires to function well. You can’t be riding on the rims during a race and expect to be very efficient.

Optimization, although more costly in the immediate term, is more cost-effective than hard-edged efficiency over the long-term. What happens if the bike frame breaks? The amount of power that goes from your downstroke and into the ground drops to zero.

We all live in this compromise: we want to increase our efficiency, but not at the cost of optimization. Let’s use a gait example. Is it more efficient to shut off your gluteus maximus, hamstrings and quads while running? Probably—those muscles are huge. They’re consuming lots of sugar and oxygen in order to stabilize the pelvis and move it over the femur and the knee joint.

In addition, they’re mostly only active from contact to midstance. They’re the biggest muscles in the body, and they don’t even help you push off. Less efficient? Sure! Why not just let momentum carry your GCM—general center of mass—over your knee joint while keeping the hip extensors quiet?

Because your femur would summarily come off your tibia, and your patella would pop off and land somewhere on the ground in front of you. Once again, the efficiency of your gait would drop to zero.

I’m not making an argument for any particular method or stride type. (I believe those arguments are there to be made, once we have satisfactorily defined what we mean by “stride type,” but not in this post). The takeaway, as I mentioned above, is that in order to optimize something to the environment—say, in order to allow our body to remain in a configuration which can adapt its footfalls to variable terrain—we’re going to be sacrificing some raw efficiency.

Is forefoot-striking or Pose the best way to optimize the body? Well, that’s a different question.

UPDATE: In this article, “Pose” refers to excellent pose technique. (This was brought up by a concerned reader on a Facebook thread.) Indeed, all running and all movement is an alternation of poses (think about the kata in martial arts). For better or worse, the question remains in the scientific and running communities: is excellent Pose technique the best way to run? Many try to detract from it by saying that it is less efficient. I believe that regardless of whether it is or not, that line of argument largely misses the point.

Principles of Training

Reflections on the Functional Movement Screen (FMS) Seminar

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Last weekend I attended the Functional Movement Screen (FMS) Level 1 and 2 seminar in San Diego, California.

I’m always looking for ways to simplify the process of correcting the gait of runners that I work with. The FMS is an extremely easy tool to use, and the corrective exercises that I learned are aggressively effective.

But before I go into all that, let me back up and discuss what the FMS is all about. The FMS started when Gray Cook and Lee Burton realized that mainstream kinesiology and physical therapy wasn’t helping a majority of people recover completely: even though injury and physical dysfunction were being rehabbed properly, very little was done to regain proper movement.

As Gray Cook likes to say, “mobility does not equate with movement.”

In other words, it is not enough to simply have active range of motion (ROM) for a particular joint in order to be able to use that ROM in an activity. While the mobility might be there, the body has to understand how to apply that mobility to a global movement pattern.

The FMS has established a baseline for competency and dysfunction of movement, and based on that baseline, has developed a corrective method to bring the body towards proper movement.

Of course, proper movement does not equate with peak performance. But proper movement is necessary to allow the body to tolerate an increased training volume, and to have an efficient training response. Training, then, must be done when there is already correct movement.

As a runner, this is humbling for me. I have a pretty good gait, and although specialists will point out power leaks here and there, the FMS shed light on just how problematic my movement is, and did so in a meaningful way. It’s not just a matter of stretching the glute med or working on the piriformis any more—that’s not how the body understands the musculoskeletal system. It understand that system through movement and gait.

The FMS speaks the language of the body, and seems to speak it well.

Already, within only a week of working on my weakest links, I have increased trunk flexion and extension capacity, and much, much better mobility in my hips and legs.

I look at the majority of runners, who enthusiastically classify themselves as “injury-prone,” or “overpronators.” But if you think about it, there’s very few runners that are “true” overpronators—very few out there who have shoulder, hip, and knee aligned in the saggital plane and still overpronate. Overpronation is born from a movement dysfunction (which of course, may have roots in musculoskeletal dysfunction).

Running is a contact sport. Think about how many times you contact the ground during a marathon. We runners need movement quality prior to training quantity to negotiate those contacts correctly.