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Allostasis: The Future of Periodization?

Table of Contents

Key Takeaways:
  • Current periodization theory is behind the times, still embracing an outdated framework developed almost 100 years ago
  • The human and it’s responses to stressors are too complicated to be predicted
  • Embracing allostasis as a new framework for treating and coaching complex humans is the way to stay as up to date as possible

Historically, periodization has been dolled out from a top down prediction approach. Coaches lay out a 4, 8, 12 week periodized plans for their athletes, insinuating that this is the path you’re likely going to progress along and follow. 

Anyone who has run one of these very specific and laid out ahead of time programs knows that things usually don’t go so smoothly, and that bumps and bruises in the plan are inevitable. These bumps can almost 100% be attributed to lack of ability to predict how things will go. If crystal balls existed, things may look differently.

Let’s look at the background of why we tend to periodize this way, and what a potential new way forward looks like.

General Adaptation Syndrome

Hans Selye first came up with General Adaptation Syndrome, or G.A.S. in 1936, coining the term in his paper Stress and the General Adaptation Syndrome¹ in 1950. The idea in a nutshell was that biologic organisms placed under stress exhibited similar phases of being. A stepwise cascade that could be predicted and counted on. The means through which he figured this out was by stressing rats (mainly placing them on the roof in Canadian winters and starving them) to see how they would respond. 

The three phases include the alarm phase, the resistance phase and the exhaustion phase. 

The alarm reaction (A.R.) can be summed up into what we call a fight or flight response. It is characterized by the so-called ” shift in anterior-lobe hormone production. This consists in a diminished secretion of somatotrophin, the gonadotrophins (F.S.H., L.H., prolactin) and thyrotrophin-which are not essential for the maintenance of life during conditions of emergency¹ and is also accompanied by an increase in the secretion of A.C.T.H. (adrenocorticotropic hormone).¹


  • This is the initial phase when the body first recognizes a stressor.
  • The body activates its “fight or flight” response, releasing stress hormones such as adrenaline and cortisol.
  • Physiological changes occur, such as increased heart rate, heightened alertness, and mobilization of energy resources.

The resistance stage progresses differently if the stressor is removed or if it persists. If it is removed, there is an ability for the organism to recuperate and repair what it needs to. “Most of the characteristic manifestations of the A.R. (tissue catabolism, hypoglycaemia, gastro-intestinal erosions, discharge of secretory granules from the adrenal cortex, haemoconcentration, etc.) disappear or are actually reversed during the stage of resistance. 

However, if the stressor is not removed, you will essentially continue to exhibit a presentation similar to A.R. until the stressor is removed. 


  • If the stressor persists, the body enters the resistance stage.
  • The body attempts to adapt to the continued stress by stabilizing physiological processes.
  • During this phase, the body continues to cope with the stressor, but at a cost. Resources are diverted away from other bodily functions, which can lead to increased vulnerability to illness or other stressors.

Finally, if the stressor continues to exist for a prolonged period of time, the organism enters the exhaustion stage. This is exhibited by impaired physiological functioning, and an inability to fend off chronic illness and disease. 


  • If the stressor persists for an extended period and the body’s resources are depleted, it enters the exhaustion stage.
  • The body’s ability to resist the stressor declines, and physiological functioning can become impaired.
  • Prolonged exposure to stress at this stage can lead to various health issues, including chronic diseases and mental health problems.

What Hans ended up pulling from these studies was stress responses are predictable and that every biologic organism will react in a similar way, and that the reaction is stemming purely from biologic processes and sources. This partly explains why periodization is the way it is now, with coaches and physical therapists alike assuming that adaptations can be predicted and planned for over broad time.

We apply stressors, out comes a response from the human, followed by an adaptation, all nice and neat. The problem is that when the rubber meets the road, predications normally fall short and it is far from neat. The idea that the body is a machine that will react according to a nice set of rules or will react how we assume it will based on logic and common sense is nothing new.

We see a similar way of thinking in things like corrective exercise, manual therapy or some popular surgeries. If we “fix” the parts, the sum will improve. But more often than not, the parts themselves have nothing to do with why the sum is having issues. When we realize that the body is not a machine is when we start to shake the misunderstandings of the past. 


When we talk about leaving the past behind for the future, we need to start to talk about what’s called allostasis. While prediction in the classic sense doesn’t work when it comes to the human, that is moreso in the context of humans volitionally trying to predict how something will go. This is normally hampered by things like a seemingly infinite number of unaccounted for factors at play, the inner workings of complex systems, and cognitive biases, to name a few. 

Prediction in the sense of allostasis is centered around the internal predictions of the human. This starts to get into the idea of predictive processing, which is the idea that instead of reaction to input from the external environment through the 5 senses (bottom up), the human predicts what will happen based on prior experiences and exposures to similar situations (top down), and compares these predictions with the sensations coming in from the external environment to shape perception. When something from the bottom up doesn’t jive with the expectation/prediction, there is an update to the top down prediction. ²

Allostasis says that the human will involuntarily anticipate or predict what it needs for a given situation and prepare for the stressor prior to it actually being applied to the human. 

Anticipating ‘needs’ before they arise, and by mobilizing a diverse breadth of neurological, biological, and immunological accommodations to counter these emerging challenges.³

Rather than reacting to what is happening, essentially being 1 step behind the stressors being applied, allostasis says that the stress response will be individualized to the context of the situation, including the specifics of the task at hand, the environment that it is taking place in, the exposure or lack of to similar stressors in the past and the general cognitive state of the human.

All this to say, responses to stressors like a training plan are complex, and vary widely from individual to individual. 

What do we do with this information?

There are a few key things to remember when trying to integrate allostatic theory into programming, coaching and being a physical therapist:

  1. Relationship and communication with the human you’re working with are key. Only the human in front of you holds the insight as to the specifics of their responses to training, so a robust feedback system must be in place.
  2. An emerging strategy is important, namely taking things one step at a time to be able to measure a response to a stressor, and make swift changes as needed.
  3. Making sure the human you’re working with is on board with and has bought into the plan can help with decreasing the cognitive load in a stressor situation. 

If you can implement these three tactics, you’re well on your way to being an amazing strength coach, as a physical therapist.

If you want to ensure your status as a strength coach in the physical therapy world, check out our course the Clinical Coach Challenge. We discuss allostasis at length in the midst of other periodization and coaching theories, principles and actionable items, all intended on giving you the tools needed to differentiate yourself in a world embracing strength more and more every day.

  1. SELYE H. Stress and the general adaptation syndrome. Br Med J. 1950 Jun 17;1(4667):1383-92. doi: 10.1136/bmj.1.4667.1383. PMID: 15426759; PMCID: PMC2038162.
  2. Ongaro G, Kaptchuk TJ. Symptom perception, placebo effects, and the Bayesian brain. Pain. 2019 Jan;160(1):1-4. doi: 10.1097/j.pain.0000000000001367. PMID: 30086114; PMCID: PMC6319577.
  3. Kiely J. Periodization Theory: Confronting an Inconvenient Truth. Sports Med. 2018 Apr;48(4):753-764. doi: 10.1007/s40279-017-0823-y. PMID: 29189930; PMCID: PMC5856877.