Training From Scratch (III): Stability (1)

Stability got FUBAR-ed by ‘functional fitness’ and this post levels the ground so we can build a (stable) house later.

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Carnap1 may not have been a success but Carnap2 sure was

In 1945, Carnap proposed a distinction between two concepts of probability which remains to this day a masterpiece of philosophical analysis and cleared the air for the generations to come. He also proposed a notational convention that never took, between probability1 and probability2 (didn’t I mention that heroes fail?).

Following on Carnap’s footsteps (let’s not be too modest) I’ll play the hero, establish a distinction between stability1 and stability2 and hope that the distinction will stick in the reader’s mind even if the notation doesn’t.

Like Carnap, I’m building on older material and in fact, short of the notation convention, the distinction is more-or-less already in McGill’s Low Back Disorders. So I’m about to do is more cosplay (a biomechanist) than play tout court.

Which is also a reminder that analytic stuff, like parasitic stuff, wouldn’t exist without what it is an analysis of. Then again, analytic stuff is therapeutic stuff which makes it more of a symbiote than a parasite. (Save for analytic philosophy which is mostly a parasite of the public funding system.)

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Analyzing stability

The first notion of stability, or stability1, is the one that everybody almost gets.


Again, by “everybody”, I mean everyone involved in physical activity stuff from the fitness-and-rehab PT/PT (should I write PT_1 and PT_2?) and the sport-and-performance athletes and coaches, to the exercise-science researchers. And by “almost gets”, I mean that they get the first half of its functional definition: the “input” part.

Honestly, I’m not sure everybody gets the “output” part. But I’m not sure they don’t get it either, as a general rule. There are however clear-cut cases where they don’t get it and we’ll see why.

What everybody gets (and what they miss out)

Most of the details of the discussion of the output part can be left for geeks-only asides. But I sure hope that you’ll read them, and to give you some reasons to do so, here’s the full input-output definition:

  • Output: an angle between certain lines originating from or passing through the Cartesian coordinates of the CoM and BoS.

In practice, we can abstract from the need of an explicit Cartesian coordinate system, as in the diagram below that I borrowed from McGill’s Low Back Disorders 3E (p. 157).

In order to decode this, we need a few auxiliary notions omitted by McGill and not represented on the diagram. For now, let’s focus on the left-hand side diagram (a) and pay no mind to angle θ.

First, look the at Big Triangle’s (BT) CoM : the projection of the position of BT’s CoM on the abscissa (the x-axis in a Cartesian Coordinate system, not represented in the picture) is called the center of gravity (CoG) of BT. If you confuse CoM and CoG, it’s not dramatic, but try not to anyway.

Second, look at the points of contact between BT and Left Small Triangle (LST) and Right Small Triangle (RST). In the context of this discussion, BT’s base of support is an imaginary line segment that spans between the point of contact between BT and LST and the point of contact between BT and RST (but see aside below).

Now, try to picture the projection of that line segment on the abscissa. In diagram (a), BT’s CoG is smack dab in the middle of the projection of BT’s BoS which incidentally is the farther out BT’s CoG can be of each point of that segment at the same time.

The reason why this matters is that BT is the simplified 2D representation of a human, and that the usual recommendation to maintain a human’s stability1 is to pay attention to “keep the center of mass over the base of support” which is short for “keep the center of gravity over the geometric center of the projection of base of support”. Below is a short video of Steve Cotter using that kind of cue for coaching the pistol squat. (Tip: watch it a 2x speed).

Here’s the thing: everything that Cotters says makes perfect sense. The cue to “sink over that base” when on one leg (03:10) for preserving knee stability incurs a risk of mixing up stability and balance. (And I’m not saying that Cotter mixes things up, because he isn’t, but it’s a risk.)

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Summing up, almost everybody gets the input of the stability1 function but some mix up the output and mistake ‘stability1 training’ with training the ability to counteract P-forces, while it should be the ability to optimize θ-angles.

Then again, that is Jane DM-level shit analysis and not everybody is that smart. Which brings me to how this confusion has spawned other mistakes and eventually bullshit.

Adding insult to injury: the category mistake

Whatever-it-is that Joe PT did in Thought Experiment #1 is inspired by two things:

  • a confusion between stability1 and balance, and:
  • the notion that increasing the intensity of an activity increases the training effect from this activity.

We’ve seen how (1) is possible, and (2) is essentially the rationale behind progressive overload (that I discussed in this post in the aside about the Law of Adaptation) so there’s nothing wrong with it.

Together (1) and (2) entail the notion that if the base of support is at its smallest, stability1 will be trained at maximal intensity while still ‘functionally’ (more on that soon). Which is, in turn, a dramatic category mistake perhaps responsible for the worst trends of the fitness industry since the 1990s (I’ll speculate about that in conclusion).

The concept of category mistake was introduced by British philosopher Gilbert Ryle in the 1940s, but it was already used in the 1920s-30s by the Vienna Circle, chief among them, Carnap (again). Here’s an example adapted from Ryle: someone has been told that there’s a marching army coming his way, watches the soldier passing by, and then asks: “where’s the army? I only saw the soldiers!”

That’s a category mistake: it asks about something (the army) as if it were a different kind of thing, or category, as what it is (a bunch of soldiers) just because the words are different.

“Where’s the legion? I only see legionnaires…”

Also, if it’s a kid asking, it’s cute. If it’s a grown-up asking, it’s retarded.

Now, assume that you want to train an army to march, what would you do? That’s easy: you would train the soldiers to march. Similarly, training stability1 in motor patterns is training those motor patterns. The stability1 demand of a motor pattern is ‘built-in’: there is no point isolating that demand to train it at a greater intensity, because if you change this, you change that (I told you that anaphora was a snag).

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A recipe for ‘functional training’

By now, you have presumably come to the natural conclusion that any training aimed at improving any performance whatsoever is ‘functional’. And if you have not, just pretend.

Functional training follows the following recipe:

  • Operationalize the performance to be improved. This step amounts to find a way to measure it, and it’s usually straightforward for sports.
  • Hypothesize a functional relation between the performance and other stuff. This step is usually grounded in some knowledge base suggesting the hypothesis that some ‘input’ drills would (measurably) improve the ‘output’ performance operationalized at (1).
  • Practice ‘input’ drills and measure the ‘output’ performance. This step is the trial-and-error phase: if performance defined in step (1) improves, the ‘input’ practice is validated; if not, start over with a new hypothesis at step (2).

Defined that way, ‘functionality’ is just another term for the principle of specificity, which is one of the basic principles of exercise science. As always, the devil is in the details: ‘functional training’ is a fitness-and-rehab buzz-phrase that is supposed to pertain to the ‘activities of daily life’ (ADLs). This complicates matters a bit, but I’ll leave that for the fine prints.

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The irony of the confusion between stability1 and balance and the category mistake about stability1 is that ‘functional fitness’ was initially the fitness-and-rehab response to bodybuilding.

During the 1990s, at the height of the bodybuilding craze (which was also the golden age of steroids), isolation exercises were the main paradigm for general fitness. But in the late 1990s-early 2000s, under the influence of physical therapists (like Gray Cook) and biomechanists (like McGill), the fitness-and-rehab world gradually realized the lack of efficiency of isolation exercises for rehabilitation and preventions of injuries both in everyday life and sports practice.

Stuart McGill mostly stuck to his science, but Gray Cook spearheaded the ‘functional exercise’ movement, eventually proposing a metric for ‘functionality’ and proposing a certification program (Functional Movement Screen™ or FMS™ ) aimed at teaching how to measure and improve ‘functionality’ ( but it’s most likely just bullshit [4])

And so, ironically, ‘functional fitness’ ended up trying to isolate physical qualities at the expense of others (Pavel Tsatsouline makes a similar point in this video). In retrospect, CrossFit® may very well have been a reaction to ‘functional fitness’ in the same way as ‘functional fitness’ had been a reaction to bodybuilding.

Didn’t I tell you that all the confusion around stability1 was responsible for the worse shit trends in the fitness industry since the 1990s? Ok, the part about CrossFit® is a bit of a speculation on my part, but it’s a tempting hypothesis.

In the follow-up, I’ll look into Stuart McGill’s effort to spreading awareness about stability2 and fight a confusion between stability1 and stability2 that plagues both practice and research in exercise science and sports medicine, and threatens any ‘evidence-based’ suggestion about what ‘stability training’ should be.

I will also argue that we can survive all that mess and train stability{1,2} in one fell swoop without giving a fuck about balance boards, BOSU® and ‘functional’ exercises, with just a few hypotheses about what matters for ADLs.



[*] This is a theoretical maximum under the assumption that each word carries marginal information. The actual information content may, in fact, be lower.

[4]^ There’s about 10 years of research on FMS™ with several meta-analyses. So far, they do not fully agree, but there’s a trend: those who support FMS™ do so with explicit methodological reserves (like this one) that do not undermine those who recommend abandoning FMS™ altogether (this one and that one). Another warning sign is that there is a joint FMS™-RKC® certification administered by Dragon Door (see here and here for Dragon Door’s history of bullshit).:


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