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  • Writer's pictureJesse McMeekin

Jacksonian Dissolution in the Training Environment

Updated: Jul 31, 2019

How this obscure theory of evolution and devolution can explain and inform our training choices.

Kind of a Mouthful

It's not so much that it's hard to say, it's just that almost immediately upon having actually said it you're impressed by the sense that this is a heavy concept: Jacksonian Dissolution! I first ran into it a few years ago at a workshop with Dr. Pat Davidson of MASS and MASS 2 fame. He'd casually written it on a white board, and for a good chunk of his lecture he kinda just let it sit there completely unmentioned. Whether or not this was his intent, I took the bait hook, line, and sinker. The nerd in me reallywanted to know what that term meant, what the heck it had to do with being big and strong (hey, it's Pat... it wasn't gonna involve too much finesse), and how I could use it to both improve my programming and sound super smart!

Actually Not That Bad

As it turns out, the concept of Jacksonian Dissolution is—while maybe not familiar—at least more comfortable than it looks. It states that as a system or organism evolves it becomes at once more flexible, more complex and—due to this complexity—more fragile. When exposed to stress, the usually complex and flexible system devolves to simpler states, sacrificing complexity for survival.


As it turns out, Jacksonian Dissolution seems almost accessible, and the more I've thought about it, the more examples I've found. (Please note that while these illustrate the general concept, they may not be perfect examples of the theory in its purest sense. Rather than worrying about that, lighten up and go with it. Better yet, dig into Dr. Stephen W. Porges' book The Polyvagal Theory for a purer application of the theory.)

Energy Systems

As the body's three primary energy systems (alactic, lactic, and aerobic) evolved they became increasingly complex—the electron transport chain and the Krebs cycle—increasingly flexible in their use of substrates as fuel, and increasingly susceptible to being derailed by environmental factors. Subject a resting body to sufficient stress and it will shift its energy production from being predominately aerobic to being more anaerobic (lactic), and if the stress is of sufficient intensity all the way back down to the prehistoric alactic system.

Planes of motion

The sagittal plane is the foundation for the frontal plane. The transverse plane is built from and upon both the sagittal and frontal planes. With limited stress we move freely through all three, but as stress accumulates we regress; normally smooth, fluid gait patterns becoming the staggering waddle of a drunk (or someone after leg day) as we lose control of all but the simplest expressions of movement—flexion and extension.

Henneman's Size Principle

A quick refresher: Henneman's size principle states that motor units are recruited in order from smallest to largest. The upshot of this is that the first muscle fibers called upon are the low force, high endurance slow twitch fibers (type I). The body's high force, low endurance fibers (type II) aren't recruited unless either increased force or power is required (heavy weight or fast movement), or as fatigue of the type I fibers sets in. Among the practical benefits of this bodily strategy is the ability to limit fatigue by relying on mitochondria-rich type I muscle fibers. Examined through the lens of Jacksonian Dissolution, we see a tendency for stress to break down yet another system with concurrent costs and benefits shifting in order to complete a given task. Heavy weight (high stress) reduces us to a more basic, more durable, but less efficient state.

Motor Control

I hadn't done a snatch-grip single leg deadlift in a while, but I remember being able to use just a little more weight than I actually wanted to, so I loaded the bar up, grabbed it, and got to work. Immediately my glutes and hamstrings said hello, my core fired up, and I managed to squeeze out ten decent reps before my grip gave out. I followed that with a Bulgarian split squat and a brief rest. Round two got a little rockier, but I only bailed on one rep. Round three? My last set of ten looked more like four sets of two or three with some nonsense thrown in between rounds. I wasn't actually any weaker, and the weight—while still certainly feeling heavy—didn't feel any worse than it did when I first grabbed it. But my nervous system was shot. I just couldn't manage all the intricacies of such a demanding movement under the increased stress of fatigue.

Forms of locomotion

Imagine the cartoon man losing his way in the desert, first walking, then crawling, and finally slithering towards the imagined oasis. The complex and flexible falling apart and ceding to more primitive forms of travel.


I worked with a client—unsurprisingly a very accomplished young woman—who's initial response to a relatively heavy weight or hard set was to say, "fudge!" We'd laugh at her rather prim use of language, and I'd inevitably do something to make her next set harder. "Shit!" came the response. Again, we'd laugh at the change, but as often as not I'd add still more weight or reps or whatever to make it just a bit harder, and finally we'd get there: "Fuck!" From buttoned-up businesswoman to swearing like a sailor, the degree of stress, fatigue, or just sheer discomfort was enough to send her backwards, dissolving her nicely-crafted shell and exposing the messy, emotional core that lay underneath.

The Stress Response

While individual examples of a theory in practice are interesting exercises on their own, I've found real practical value in looking at the training session as a whole as a dissolving event. A friend of mine, Kyle Dobbs of Compound Performance, has said that training comes down to stress management. That's a pretty succinct summary of any intelligent training model, and Jacksonian Dissolution is simply a way of understanding what happens as we apply stress to various bodily systems. The aim of applying stress is to temporarely degrade or dissolve a system; following training you are slower, weaker, and less coordinated than you were beforehand. But stress drives change, and the temporary degradation in abilities ultimately leads to lasting improvement.

The stress response and all it’s requisite components—glucagon, epinephrine (adrenaline), norepinephrine, cortisol, growth hormone etc.—is one of the human body’s most adaptive and beneficial mechanisms. Stress—in the right doses and with adequate recovery—is tremendously good for us! And Jacksonian Dissolution can serve as a window into our stress response. As we visibly devolve into sweaty, swearing, slobbering beasts externally, a corresponding shift is taking place internally. “Beast mode” is as tired as calling yourself “alpha” (neither really means much to me), and this is not about the posing and posturing that comes with either. You can’t fake a savage state and expect to reap the same rewards as someone who’s descending the evolutionary ladder in response to the visceral threat their workout poses. 

Additionally, generalized stress isn‘t enough for an efficient training stimulus. Stress should be a sniper rifle, not a shotgun, and a workout that leaves you panting and nauseated may or may not be driving the change you’re looking for. Jacksonian Dissolution looks at individual systems, not entire organisms, and while there’s sure to be some overlap, say, between muscular fatigue, energy system recruitment, and language use and processing, it’s important not to seek stress for its own sake.

The Training Environment

If we accept that training is simply stress management, Jacksonian Dissolution is at once a measure of the stress being applied, a way to understand the effect(s) of that stress upon a given system, and a framework for how to apply that stress in a safe, effective manner.

As a Measure of Stress

I'll be as clear as I can be—and will close with the same thought for good measure—effective training should be terrifyingly hard at points. I want people reduced to their baser selves, far removed from the niceties of our sedentary society. And it's a rare person who will go there voluntarily, who signs up for what at times amounts to near-torture. In these moments part of my role is to ensure that things are as hard as they need to be, and Jacksonian Dissolution offers a fairly robust way to examine your response to stress. Your posture, body language, the way you breathe, word choice, movement quality, the length of your sentences... all of it is a source of feedback, and I need to see at least some of it deteriorate. Training can't stay pretty all the time.

Having hopefully having argued convincingly in favor of applying real, meaningful levels of stress via training, it is every bit as important that we consider the both the allostatic load—total stress—an individual is under as well as their strategies to manage that stress. Are their nutritional, sleep, and leisure activities condusive to high or low applications of stress? Do they have a social system they can lean on for support or one that requires support from them at the moment? Don’t shy away from stress, but be aware that we are almost literally playing with fire; we want to toast the marshmallow rather than set it on fire so to speak.

As a Way of Understanding the Effects of Stress

Perhaps the simplest way of understanding a system under stress is via the particular model of Jacksonian Dissolution. Under sufficient stress a system will revert to simpler, more primitive alternatives.

As a Guide for Stress Application

In designing a training program it's important to consider what kind of stress is best suited to the person, the movement, and the degree of fatigue they're experiencing (early vs. late in the workout, for example).

Our big, sagittal movements lend themselves nicely to heavy loads and high fatigue. I can deadlift, squat, press, and row through enormous fatigue. I could teach Hodor a trap bar deadlift. What's more, that same fatigue is likely beneficial to those movement patterns, providing I maintain some degree of movement proficiency throughout.

As movements become less stable or more complex stress needs to be applied in a different way. The nervous system already perceives the body's position as an elevated source of threat, and heaping on too much additional stress can end badly. In these cases additional stress—in the form of too much load, too little rest and the like—can actually detract from the intended training effect by allocating resources to the wrong stressor.

When we introduce speed and power into the mix things get even dicier as fatigue sets in. Box jumps are a terrific, low-intensity way to develop explosive power, but done as a "finisher" or as part of a circuit—particularly with an athlete jumping back off of the box—the injury risk they pose may not be worth the reward. In addition to the potential for injury, the effect of the stress may again be misplaced. Stress is specific; if the intent is to develop power and explosiveness, the fatigue the body is under will limit the amount of power being expressed and therefore developed.

How you fit the puzzle pieces together will vary tremendously—we haven't even considered the athlete/client, their goals, ability level and the like—but certain overriding principles can and should guide our choices regardless of who we're working with. Stress drives adaptation, but stress is system-specific. A hard workout may not be an effective one.

A Slobbering, Sweaty Mess

As promised, I'll leave you with what I feel is the most important reminder this particular theory has to offer us: we need stress. It shapes us. And stress is ugly, messy, frightening, and primitive. Stress is savage, and at times you need to meet it head on. Think about how and when you apply stress, but when it's time to get to work, be a savage.

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