What’s in a word: why we need to think beyond flexibility and mobility

“Strength and conditioning”—the collective sobriquet most often assigned to the profession of training athletes to soar toward the upper limits of their potential—is an amalgam of two tremendously elastic and ill-defined words. They are among many terms in the coaching lexicon that are, most often, used without much concern for their precise meaning.

Imagine a carpenter asking for “a saw,” a mechanic asking for “a wrench,” or a surgeon asking for “a clamp” . . . without any specific modifiers connected to those words. The kind of saw, wrench, or clamp will certainly make a difference in the outcome of their work. Why is it that coaches and athletes regularly converse using amorphous, waste-basket terms and assume that all will be understood? Wouldn’t we find the job of coaching much easier if we took time to learn and use a more precisely codified taxonomy?

» Learn more: Steve Myrland demonstrates some sets to help develop connected range of motion.

Two more terms that sail along, untethered, unmodified and unqualified by clarity, are “flexibility” and “mobility.” Both hint at things that are vaguely understood on a subliminal level, but which lack essential focus. And both terms seem to beg for a number; a quantified definition. That is where the problems begin.

Quantities in human performance are meaningless when they are disconnected from specific qualities. Often, they are even inimical to the process of development and improvement because terms of quantity—especially in sport—tend to light the “more is better!” lightbulb in the minds of coaches and athletes. But: more isn’t better. It’s just . . . more. And more is often dangerous.

The problem with quantification: more isn’t better

Consider the gold standard “sit and reach” test. How many millions have been spent on these silly boxes that happily and efficiently spit out numbers when a student sits and reaches, pushing the slide indicator on the top of the box? Every student understands that pushing the slide as far as possible is the goal of the test. More is better, right? And—sadly—almost every teacher using this test believes the same thing. A big number is good (“You have great mobility!”) while a small number is . . . well, concerning (“You really need to work on your flexibility!”).

This is the zenith of useless, low-hanging-fruit measurements. It takes mere seconds to test each student and the test offers a nice, whole-number result to log, graph and point to by way of justifying the physical education experience. It does not actually measure “flexibility” so much as it encourages hyper-mobility. Students, with growth-plates wide open and little kinetic awareness, make every compensatory “Gumby” movement possible: hyper-extending the knees, rounding the back (expanding posterior vertebral spaces while crushing the anterior spaces) to push the indicator slide a few centimeters . . . more. If anything “good” results on this test simply tell us which growing young bodies might be at the greatest risk for serious orthopedic injury.

Of course, the real goal of physical education (and of strength-and-conditioning programs) is to help individuals move better. So: a static measurement, taken in a position that is virtually irrelevant to kinetic survival is pointless.

What is flexibility?

What do we mean when we say “flexibility”? How do we define it and how do we evaluate it? If athletes can be said to have “good” flexibility, surely they can also have “bad” flexibility. If it’s good, why is it good? How is it good? Where is it good? And if it is bad, why, how and where is it bad? And how is it improved?

Does a fourteen-year-old female volleyball player with valgus knees, hyper-extendable elbows and tight hamstrings need to stretch? And if she stretches, what, exactly, is she stretching? Muscles? Tendons? Ligaments? All of the above? What effect will “stretching” her hamstrings have on those valgus knees and the risk of injury they represent?

Let’s take a step back to answer these questions. If we hold to the idea that a body in motion is, by definition, a kinetic chain, then the chain metaphor has to mean something. Here are two essential truths about chains:

  1. A chain has no function without tension (just try pushing one); and
  2. A chain is only as strong as its weakest link.

The throwing events in athletics provide superb visual illustrations of these two statements. Slow-motion video reveals how each segment of the body must connect with its neighbors to produce a force that is sufficient to propel the implement with focused accuracy (and without fouling). Any disconnect (an elbow that flexes when it should extend; an ill-timed shifting from proximal loading to distal release, etc.) will yield an unsatisfactory result (and possibly, an injured athlete).

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Similarly, the optimized, synchronously opposed ground-contact and recovery of a sprinter’s legs is required to produce speed. Each hip must permit fast swing capability for each leg through the full range of high-speed gait, but must also be fully charged, loaded and co-contracted for a fraction of a second at ground-strike. If all the involved muscles, from toes to fingers, fail to achieve this alchemy at the precisely defined moment, the body creates shock absorbers when shock transmitters are needed. The effect of massive ground-strike forces must then be borne by structures that are far more brittle, breakable and ill-adapted to bear them than the momentary (magical!) rigidity achieved by pliant muscle tissues organized to perform and protect those structures at the appointed moment.

We think of gymnasts as having “great flexibility,” but the range of motion required to score well in a gymnastics meet is, in many cases, achieved by breaking down the body’s connective-tissue limiters. It is athletic Darwinism; it is like disabling the brakes on a car. Some genetically gifted, physically advanced young gymnasts survive the process, but many suffer injuries resulting from too much stress placed upon a kinetic chains too unstable to maintain control in critical (force production / reduction / redirection) moments.

Clearly, what matters most is the integrity of the physical connections required to produce movements that are efficient, effective and robustly durable.

Rethinking the lexicon

Clearly, while simplistic notions of flexibility and mobility may be adequate for gaining a sense of where a growing body is on the physical development scale, they are inadequate to the task of understanding where an athlete is on the spectrum of physical performance.

And, clearly, there must be a better way of (and better words for) conveying the quality of kinetic connectivity. Physical therapist Gary Gray coined the term “mostability” in an attempt to capture the concept in a word. Mostability is defined as the greatest range of motion over which an individual has control. Not bad.

A nice word choice for the elusive mostability quality might be “suppleness”—as in the action of tall, healthy trees in strong, gusty winds. A supple tree bends, but does not break. It is a good metaphor for the kinetic-tensegrity that defines athleticism and physical grace, and an agile rebuke to the standard notion of muscle function: muscles are not agonists and antagonists with respect to each other; they are synergists. Trees are connected from roots to top branches. If there is disconnection (a section of dead wood), the wind will prevail, and the tree will break. Similarly, when we see examples of dyskinesia (and they are everywhere), what we see are breakdowns and disconnections in the kinetic chain.

If bodies create strength and range-of motion in disconnected ways (absent qualifying constraints) . . . connecting those bodies to functional athletic movements is possible, but unlikely. Flexibility . . . mobility . . . these are among the blurry, quantitative terms we use to describe and define important physical qualities. By understanding where the terms fall short, we as coaches can better understand our goals in training and help create connected and useful physical qualities in our athletes.