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All posts for the month July, 2012

No matter what kind of runner you are— elite, recreational, or novice— it’s a good bet you want to run farther, run faster, and run with less chance of injury. Or, just to run again with childlike joy and abandon. To these ends some think, for instance, that running success lies in buying expensive, medicating shoes. Others, however, know less is more. They reason that by learning correct running form, that is, how to run in harmony with Nature and the physics that shaped our bodies and prescribed our movements they can dispense with the hype of empty product and promise. And it’s true.

Why add weighty, wedge shaped shoes that promote injurious heel strikes when our inherent springiness provides all necessary support and shock absorption? Why waste energy and mental focus on efforts like push off and knee drive when we’re already hard wired to run perfectly without? The facts are that human bodies are effectively the same because they developed under the same physical forces, so naturally we can all run safely and efficiently. Naturally, of course, means runnin’ nekkid— barefooted— though not all runners welcome such exposure. While barefoot provides better feedback, correct running form can be accomplished in shoes, too.

But what exactly is this correct running form?

Running is controlled falling. Every run begins with a lean in the desired direction and the body falls forward like a felled tree. We let go of the ground with one foot, re-catch it with the other and repeat over and over, on down the road. Simple, eh? But to correct running form, we must cultivate perception.

Let’s first frame our discussion.

Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.

Antoine de Saint-Exupery

Again, since we are more alike than we are different, meaning that we come equipped with the same biomechanical gear and go about our day to day governed by the same natural laws, we all run the same way. What may appear as unique personal style, runner to runner, is still fundamentally identical for everybody — Pose, Fall, Pull [1]. Parsimony is perfection.

So, correct running form starts at mid stance, with the Pose [2].

Pose

The running Pose is something we already do. It’s common to all runners. That’s you, me, the fastest man in the world Usain Bolt, and those joggers we run past in our neighborhoods. The running Pose is a singular point in space and time that separates the previous stride from the next, and becomes a standard by which we differentiate good technique from bad. Correct running form is distinguished, simply, by getting in and out of the Pose “on-time” [3]. This timing, though, requires context— we’ll get to that, later.

Picture of Runner in the Running Pose.

The Running Pose

Notice at mid stance, in the running Pose, how the ankle, knee, and hip of the support leg are bent. When bent just-so these joints become a magnificent musculo-skeletal spring. This spring stores elastic energy gathered from the previous stride and releases it in the next [4]. The spring is fully compressed at one point, precisely when bodyweight, or the general center of mass (GCM)— think of the GCM as a marble lying roughly behind and below the navel— is directly above support on the ground.

Support?

Obviously it’s the foot. But is there a preferred place on the foot to land when running? Could it be the small, hard, bony heel as sellers of cushioned running shoes would have you believe? Or, is it the wide, malleable ball of the foot where sensory receptors lie, where athletic balance resides, and which allows the foot to become a lever that activates our biomechanical spring (alongside additional elastic return provided by the plantar fascia and the foot arch itself)? Find out for yourself by taking off your shoes and socks and jumping rope. Or just imagine you’re jumping rope. You’re bouncing, bouncing, bouncing on the balls of the feet. Now, land on your heels. Ouch! Right? So, instead of creating a potentially injurious impact transient [5] that wouldn’t normally exist without crashing down onto a heel strike or some other active, reaching landing— aka over striding— perhaps it makes sense to let the ball of the foot just drop to the ground beneath the hips first so that bodyweight can instantly begin loading the spring.

It’s helpful to note that this musculo-skeletal spring system exists as our bodies because our earliest terrestrial forebears would have instinctually utilized precisely this alignment as they began running, which over the eons of human descent allowed Nature to fully fashion our “modern” skeletons. Form follows function. Bones grow to suit their use [6]. And so the Pose segues into the Fall.

Fall

From the running Pose— remember, it’s mid stance— we stand on the precipice with our biomechanical spring coiled and ready to lift us up so we can again give ourselves to gravity and fall forward, accelerating at 9.8 meters per second, per second (9.8m/s2) into the next stride, and the next, and so on. Some, however, say we can’t use gravity to accelerate us forward in running because it’s strictly a downward force, mathematically it zeros out and no work is done. Well, while math isn’t my first language, I’m confident that even if such an idea might parse on paper as a snapshot of assorted forces, in the real world it’s a mistake to try and understand a dynamic activity such as running by describing it in static terms.

So I ask,

If a tree falls in the forest and no mathematician is around to zero it out, did its center of mass move horizontally from point A to point B under the pull of gravity?

Exactly! And this is where the magic happens.

Pose, Point A...

Fall, Point B...

Off Support...

Our bodies, like the tree, can be represented as a falling rod [7], [8] by drawing a line from the ball of the foot up to the center of mass at mid stance. As the GCM passes over its support, sequential video frames show the rotation of the falling rod during ground contact in a runner’s stride and the resultant points A to B as horizontal movement. (Beyond point B support is lost.) It’s here where running speed begins, where the musculo-skeletal system redirects gravity, and where the illusory idea of “push off” is dispelled. For starters, any push can only be upward. Think of an analog clock face displaying 12:04. Between the hands, within this cone of support is our range of fall. A push here is far more vertical than horizontal [9], and where our biomechanical spring does its job. Next, to push a runner forward a force greater than the mass of the runner must be returned [10], but posterior ground reaction is always well below bodyweight.

Ground Reaction Forces Diagram

GRF Diagram of Heel Strike Stride

In this GRF diagram [11], the big hump is vertical ground reaction, represented in multiples of bodyweight. Maximum is at mid stance. The preceding spike is the impact transient of heel strike. The small wave below depicts anterior and posterior ground reaction, respectively— frictional forces, about half of bodyweight. Again, any apparent push off belies physical reality— no one runs until they fall. Ultimately, ground forces provide the vertical support and friction that allow runners to fall through a usable range of anywhere past 0° up to 22.5° [12], without slipping [13]. What’s more, ground reaction is about the same for faster runners as for slower runners [14], at the same lean angles. Faster runners just fall through a greater range. Plus, maximum horizontal acceleration occurs before peak posterior ground reaction [15].

Video Still Shots of Usain Bolt Running 100m World Record

Usain Bolt, 9.58 100m World Record

For instance, in the above video stills [16], from the moment his forefoot touches the ground to the instant he releases it, all within about 1/10 second, current world’s fastest man Usain Bolt gets on and off of support— where his full bodyweight is applied to the ground— in half that time. He effectively holds the running Pose while he allows himself to hinge on the ground from 0° to better than 21°. This lets gravitational torque provide the acceleration [17], obviating any need for horizontal push off. Note too, how his joints remain bent throughout. Bolt also runs with a correspondingly quick cadence, or foot turnover of more than 4 strides per second which allows him to keep pace with his range of fall as it also potentiates inherent springiness [18]. This is in large measure his advantage. He feels the natural, gratuitous forces of gravity, ground reaction, and soft-tissue elasticity better than his competition, and has conditioned his neural system to harness them all. His success can be defined in terms of superior perception and skill. Best of all is that within this same context we can cultivate our own running prowess— even if less electrifying— with one simple action.

Pull

While we normally Pose and Fall just fine, most of us Pull each foot from the ground a little too late. Once past support we’ve accelerated, we’re unweighted, and we’re ready to release the ground, yet we tend to hang on. Correct running form requires that we pick up the foot “on time” to change support [19]. But before we get to this all-important timing, let’s look at one more thing: pulling the foot versus the common prescription of lifting the knee.

The Pull is economical, whereas driving the knees forward multiplies running effort! Do the math. Proportionally, a thigh weighs in at about 11% of bodyweight, a foot less than 2% [20]. Consider with your own bodyweight how that difference would be magnified over some 43,000 steps of an approximately four and a half hour marathon, the median finish time for United States runners [21]. Notice too that former world’s fastest man, Michael Johnson’s repeated record breaking performances and his “peculiar, reliable form” [22]— very Pose-like, by the way— debunked high knee lift even for elite sprinters. What’s more, when running our knees swing forward anyway through natural reflexive coordination, and because lifting the foot itself shifts the center of gravity of the lower limb. Ultimately, when our support foot releases the ground on time the other foot naturally touches down beneath the center of mass, as our bodies simultaneously fall into the running Pose. The Pull, then, is the one meaningful action in running [23].

Now here’s the rub, or rubato. On-time means an instant after the body has passed ahead of mid stance and has fallen through its speed-appropriate range. I’m reminded of the Van Halen song, Hot for Teacher where David Lee Roth— that’s right, guy who quipped “I tried jogging, but the ice cubes kept jumpin’ outta the glass”— comments, by way of contrast, on this same internal arbiter— perception— with the phrase, “I don’t feel tardy.” But after early childhood most of us lose access to this inborn sensitivity because our awareness is deadened by cultural preferences and specialized footwear [24], [25].

You see, the lifetime of sensory deprivation to which we’re sentenced by social mores— in particular, confining our feet in shoes and socks, often before leaving the bassinet— renders our feet lame and ineffectual locomotor organs. (I wonder whether our behavioral environment will cause us to eventually forfeit our feet altogether, through disuse, as did horses. [26]) In shoes, the vital communication between the ground and the hundreds of thousands of sensory receptors underfoot is so muffled [27] it becomes tough to know whether we’re on support, or off. Whether we’re at or past the threshold between falling forward and falling down. So when we do Pull, we’re usually tardy. Given that shod feet can’t provide timely notice, and inasmuch as that interferes with spatial, body position cues— if we cannot feel it— how might we Pull on time?

Since no one rings a punctuality bell we must find ways of discerning whether we’re late or on time with the Pull. That is, if we want to revive our inherent physical fluencies, and start using correct running form. Curiously, some don’t. But for those of us who do, by holding the mental image of Pose running, viewing video clips of ourselves and others in motion, training in synch with a metronome, incorporating some barefooted sessions on hard surfaces into our workouts, and by practicing a handful of specific exercises— jumping rope, hopping, skipping, among others— we can at once improve our running mechanics, and begin rekindling our sensitivity to the point where any errant step registers immediately, and is adjusted automatically. Success— remember, to run farther, run faster, and run with less chance of injury, and otherwise savor the joy of running— asks only for attention, practice, and patience. On the flip-side, shin-splints and ilio-tibial band syndrome, a plodding pace, and undue fatigue demand heroic interventions and creative excuses.

Success

A decade ago even while wearing shoes the Pose Method skill set was easy for me to grasp. Injury evaporated, and running became more enjoyable. Perception though remained elusive, that is until 2005 when I began “runnin’ nekkid” in earnest. Since then I’ve learned to feel, because without shoes I can feel correct running form. But, unshod or not the prescription remains no more and no less: Pose, Fall, Pull. Perfect!

Video Clips—

References—

  • 1. Romanov, N. (2002), Pose Method of Running, p. 134.
  • 2. Romanov, N. (2002), Pose Method of Running, p. 55.
  • 3. Romanov, N.. (2009), Pose Method of Triathlon Techniques, p. 104.
  • 4. Fukunaga, T., and Matsuo, A. (1981), Ergonomics, Vol. 24, No. 10, “Mechanical Energy Output and Joint Movements in Sprint Running,” pp. 765-772.
  • 5. Lieberman, D. et al, (2010), Biomechanics of Foot Strikes & Applications to Running Barefoot or in Minimal Footwear, “Biomechanical Differences Between Different Foot Strikes.”
  • 6. Morton, D. and Fuller, D., (1952) Human Locomotion and Body Form: A Study of Gravity and Man, pp. 28-29.
  • 7. Brown, G., (1912), “Note Upon Some Dynamic Principles Involved In Progression.”
  • 8. Morton, D. and Fuller, D., (1952) Human Locomotion and Body Form: A Study of Gravity and Man, p. 131.
  • 9. Cavagna, G. Saibene, F., and Margaria, R., (1964), “Mechanical Work in Running.”
  • 10. Newton’s Third Law of Motion— equal and opposite.
  • 11. Wu, K. (1990), Foot Orthoses: Principle and Clinical Applications.
  • 12. Romanov, N., Payanzin, A., (2006), Book of Abstracts, ECSS Lausanne 06, “Geometry of Running,” presented at 11th Annual Congress of the European College of Sport Science (Switzerland) July 5-8, 2006.
  • 13. Margaria, R., (1967), Biomechanics of Human Locomotion, “Biomechanics and Energetics of Muscular Exercise,” p. 128.
  • 14. Kugler, F., Janshen, L., (2009), Journal of Biomechanics, “Body Position Determines Propulsive Forces in Accelerated Running.”
  • 15. Fletcher, G., Marcus Dunn, M., Romanov, N., (2009), “Gravity’s Role in Accelerated Running— A Comparison of an Experienced Pose and Heel-Toe Runner.”
  • 16. Romanov, N., (11/3/2009) “Distinctive Characteristics of Usain Bolt’s Running Technique.”
  • 17. Romanov, N., (2009), Pose Method of Triathlon Techniques, pp. 335-354.
  • 18. Cavagna, G. Saibene, F., and Margaria, R., (1964), “Mechanical Work in Running.”
  • 19. Romanov, N.. (2009), Pose Method of Triathlon Techniques, p. 104.
  • 20. Williams, M. and Lissner, H., (1962) Boimechanics of Human Motion, p. 136.
  • 21. 2011 Marathon Statistics and Report.
  • 22. Jere Longman, (4/29/2001), New York Times: Track and Field; “3 Sprinters Chasing New Goals.”
  • 23. Romanov, N., (2009), Pose Method of Triathlon Techniques, p. 92.
  • 24. Rossi, W., (10/2002), Podiatry Management, “Children’s Footwear: Launching Site for Adult Foot Ills,” pp. 83-100.
  • 25. Robbins S., Gouw G., (2/23/1991) Medicine and Science in Sports and Exercise, “Athletic Footwear: Unsafe Due to Perceptual Illusions,” pp. 217-24.
  • 26. Morton, D. and Fuller, D., (1952) Human Locomotion and Body Form: A Study of Gravity and Man, p. 33.
  • 27. Howell, D. (2011), “Foot Anatomy 101- Biofeedback.”
  • 28. Thompson, H., (1983) The Curse of Lono, p. 27.