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Ian Adamson - Stability for Runners by Ian Adamson from Healthy Running

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Stability for Runners by Ian Adamson from Healthy Running

(Ian Adamson is 7x World Champion, 3x World Record Holder, X-Games Gold Medalist, President International Obstacle Racing Federation, former editor at Winning Magazine, writer for Triathlete, Inside Triathlon, Competitor and senior contributor to Adventure Sports (since 1996)

In the last article we discussed the essential bio-mechanical requirements for runners:

·        Stability

·         Mobility

·         Strength

·         Fitness

These three are closely interrelated however for simplicity we will dig a little deeper into each separately. If you think of your body like a car (or bicycle or airplane), you need strong stiff chassis to maintain efficiency and control. If the frame and connections are loose and worn out, the whole system is inefficient because energy bleeds out every time it twists and sags. The handling is terrible, because it under-steer, bottoms out on dips and rolls around in a straightaway.

Don’t despair if your body is like an old jalopy, and don’t get too cocky if you think it’s a finely tuned sports car - we’ll show you how to address this in a subsequent article. Before we get there though, it’s useful to know a bit more detail.

In the context of running, stability is our capacity to maintain alignment and balance throughout the gait cycle, and this is critical (and most obvious) when the forces are at their highest. The maximum vertical load in a running gait occurs when you are in mid stance, when your body has reached its lowest point and your foot is approximately under your center of mass1. Your center of mass is located behind and a little below your belly button if you are upright and maintain good posture.

On a rudimentary level, running involves a series of single leg stances alternated with a “flight” of float phase.

The running gait is a mass-spring-damper mechanism3, with the body is at its lowest point in mid stance and at its highest point in mid flight. Depending on step rate, runners move four to six inches vertically between mid stance and mid flight, but this can be as low as two inches for runners with a high step rate.

The amount of vertical oscillation is somewhat dependent on how much flight time the body has, which is in turn influenced by step rate and gait style (which we will look at in a movement pattern article). The slower the step rate, the more time the body is in the air and the longer time it has to fall, just like Newton’s apple under the influence of gravity. The length of time each foot is on the ground (in stance) is also a factor, but for the most part we use step rate as the primary determinate of vertical motion4. On a very basic level, 85 to 95 steps per foot per minute is optimal for efficiency for most running speeds, just like cycling cadence.

As a result of the increased vertical forces in mid stance (2.6x body weight for an efficient runner), you have to stabilize your entire body column to maintain alignment. This means every joint, muscle, tendon and attachment from your toes to your nose.

To evaluate this, start by standing facing a full length mirror so you can see yourself head to toe. Make sure you can easily identify your anatomical features; wear a swimsuit, trisuit or nothing at all (in private unless you are an exhibitionist.) Now do the following*:

1.     Stand on one leg with good posture, specifically maintaining an upright “tall” stance, head level, shoulders relaxed and no bending or leaning.

2.    Slowly flex your knee, hip and ankle so that you lower into a shallow single leg squat. This should be done keeping your foot flat to the ground and with hands on hips.

3.    Repeat this exercise on a one second count down and one second count up for 30 seconds (15 repetitions.)

4.     If you do any of the following you lack stability:

a.    Loss of contact on any part of your foot

b.    Knee doesn’t track straight (wobbles, makes a circle, tracks in or out)

c.    Pelvis not level (hip drop, rise or rotation any direction)

d.    Torso out of alignment (leaning or bending in any direction)

e.    Loss of balance (waving arms, wobbling, shaking, rocking, etc.)

Now imagine your knee/hip/spine is out of alignment each step and this gets amplified as you fatigue. If your knee dives in (medial of your second toe) you are loading the joint unevenly and the connective tissue has to compensate. In this case the muscles, tendons and ligaments supporting your knee are stressed and consequently the upstream and downstream joints and supporting tissues.

(If you are injured please do not do the following activity). To feel how misalignment due to instability affects your body, assume the single leg stance position and lower yourself into the squat as described above. Holding the flexed position drop your free hip so your knees knock together and reposition your trunk to re-balance. Notice the increased force on the supporting tissue around your knee and hip. If you watch the NBC television coverage of the IRONMAN world championships you may remember seeing people in the back of the pack with this body position. Many runners do this to some extent as they fatigue, just make sure it’s not you!

Next article, how to fix yourself!

References

* From “Run Like an Athlete” by Jay Dicharry, available on Amazon.

1.    Lee CR & Farley CT, Determinants of the center of mass trajectory in human walking and running, J Exp Biol 1998:201 (pt 21): 2935-44

2.    Novacheck TF, The biomechanics of running, Gait and Posture 7, 1998:77-95

3.    Nikooyan AA & Zadpoor AA, Mass-spring-damper modeling of the human body to study running and hopping: an overview, dep. Biomech Eng, Delft University of Technology, The Netherlands 2011

4.    Heiderscheit et al, Effect of step rate manipulation on joint mechanics during running, Medicine & Science in Sports & Exercise, 2011:43-2







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