Allostatic Load
A dissection of an important concept for health and performance
I have previously mentioned allostatic load and that piece, on why we aren’t physiologically frail, is definitely worth reading (or rereading) but I will expand on and explain the allostatic load concept more in this piece. This is on the heels of a conference I attended recently where I got to chatting to one of the researchers/presenters about his work. In short, he was an author on a recent paper bringing into question relative energy deficiency in sport (RED-S) as a syndrome. The crux of the argument is that the issue is rarely SOLELY an energy problem (and that allostatic load is relevant).
It is worth noting, that ‘allostatic load’ is a concept, which may well be ‘true’ but it is impossible to prove (or disprove). Perhaps another way to think of it is as a model (and as I’ve written more times than I can remember - all models are wrong, some are useful). To be intellectually honest, the way in which I use the term allostatic load diverges from where medicine has ended up taking it, which is much more severe. It’s likely the authors involved in continuing to progress the field of allostatic load (predominantly in psychiatry) would suggest my definition is encompassed in theirs but they’d also suggest that theirs is much more broad.
Without getting bogged down in semantics and acknowledging the above let’s discuss when things further.
What is Allostatic Load?
As mentioned above there are established definitions of allostatic load and overload. Having said that, in this article I will use the term to mean the cumulative stressors on the body. That is, the allostatic load that you face is the sum total of stressors on the body. These can be positive or negative (that is ‘stress’ adding or subtracting) and the total load is, of course, the net of these.
Adaptive Reserve
Perhaps a helpful, related concept to ‘allostatic load’ is ‘adaption reserve’. This was introduced to me by a previous boss of mine Assoc. Prof Tony Shield. In short, you can only adapt to so much, and the amount of adaptation you have left is your adaptive reserve. This will wax and wane depending on stressors you are under. You can see, this is in effect the inverse of allostatic load in concept.
How Does the Concept Apply to Health and Performance?
In essence, the concept of allostatic load suggests that you should be considering all stressors in your life, rather than just the obvious ones. As mentioned above, the ‘net’ of the situation is important, and some stressors can be contextual. For example family may be a net stress reliever but during times of illness may add stress.
Of course, things like diet, sleep and exercise are big levers here (note exercise both adds and reduces stress in some cases - more on this later). Similarly stress management (another core pillar of health and performance), plays a huge role in your allostatic load (or indeed adaptive reserve). The other significant lever is ‘stress’ as we would think about it in the common vernacular (more specifically psychological stress). When most think about stress they probably envisage a mixture of work/study and maybe the aforementioned family.
Beyond these stressors, though, there are many others. These include environmental stressors (more on this in the piece I linked to in the first paragraph) which include noise, light and even temperature/humidity.
This is FAR from an extensive list, but the goal was to open readers minds to the potential that stressors are far beyond the first 3-5 things that come to mind. In fact, some stressors are probably so individual and insidious that we can’t be sure what they are - I write this not to scare readers as much as paint an appropriate picture (again, go read the piece linked at the top about our frailty or lack thereof).
What Does This Concept Mean for Health and Performance?
The most pertinent answer to this question is that areas and aspects of our lives don’t exist in a vacuum. Which is to say that assuming stress from one part of our life doesn’t impact another is absurd. Similarly, our adaptive research/tolerance for stress is limited and all comes from the same ‘bucket’ so to speak. This means that in periods of greater stress in one area, we probably have to reduce stress in another area (or we should try).
In practice, this means when we know we have stressful periods coming up, we should do what we can to remove stress from other areas ahead of time. An example from my time working night shifts (particularly physiologically stressful as sleep is often compromised and psychological and general physiological stress of changing time zones in effect is increased) was that I would batch prep my food for overnight for the duration of the nights, ensure I still exercised and protected my sleep periods as best as possible. During that time, the exercise I did was with the goal of doing something but nothing too stressful.
The Net Effect
It is worth spending a moment to discuss something I have continued to allude to in this piece. That is, ‘the net’ of a situation. In short, some activities are not necessarily a stress inducer or reliever but are both in different doses, and thus the ‘net’ of this is probably what is relevant. Take exercise for example; it can be a stress reliever for some (myself included) but intensity and duration matter, at some point this tips over into more stress additive. I mentioned family earlier in the piece and whilst most would agree family time can be a great stress reliever family gatherings can often be the opposite. Another example that will help drive the point home is that of the holiday from the holiday. We have all had a holiday that was quite hectic, gotten home and thought (or said to a friend/colleague) “I need a holiday from the holiday.”
The point here is that most things are a mix of stress adding and relieving (a shade of grey perhaps rather than the black and white). It’s worth considering this and acting appropriately in considering them.
Injury Risk
Many coaches will ease off athletes during high stress periods, intrinsically knowing that they need it (perhaps this is good evidence of this concept of allostatic load in itself). To further bolster this, there is research (see below) on injury rates during periods of high stress, indicating they increase.
I have personally felt the brunt of this, injuring myself when intensifying exercise during exam periods previously (to be “old and wise you need to be young and foolish” - I am working on the latter having well and truly achieved the former).
Training Load
It is pertinent to modify training loads (for performance of any sort or indeed health) around other stressors, predominantly because this is one of the few variables we can control. Of course we can work to recover more, focus more on stress management etc, all of which I have mentioned, but training modification for many people can be a large lever to pull in this realm (again, how big a lever is really about the net effect for the individual which will vary by individual).
This speaks to a concept that is related and important with respect to training. Specifically":
It’s the load you can adapt to that is important, not the load you can perform.
As such performing a similar load when less adaptive reserve is present, or you’re less able to tolerate load, may be less than ideal from both an adaptation and an injury risk standpoint.
Perfectionism
One specific area that seems to impact allostatic load as a confounder and force multiplier at times is perfectionism (hello my fellow Type A personalities). This is closely tied to the above discussed concept of ‘net’ outcomes of behaviours. It is also something I have discussed previously in this newsletter.
In short, there is the potential stress or stress relief of the behaviour in question; exercise (or not), diet and sleep (or lack thereof) for instance. But our perfectionistic want to optimise, or feelings of guilt around not being perfect, can be their own negative stressor. For example, stressing around not exercising perfectly, or having to make a dietary compromise, is probably worse than making an even worse decision from an exercise or nutrition standpoint but not stressing about it.
There is no firm quantification here, and everyone is different, but the concept should make sense. In short; the enemy of good is better, so don’t compound things with your stress about them.
Hormesis
The simplest explanation of hormesis may be “what doesn’t kill us makes us stronger.” This is not necessarily always the case, but it certainly applies in physiology fairly often. Some examples include exercise, heat and aspects of diet (specifically plant polyphenols).
An article focussed on allostatic load is incomplete without a consideration of the role that hormesis plays in allostatic load. There is the reductionist temptation to suggest that stress that is imposed with the goal of hormesis should be avoided, but like most things this isn’t an black and white situation, it is more a shade of grey. It is about when and how, not dissimilar in many ways to my recent article discussing novelty vs stability.
In a world where we are more connected and stressed out (in many ways) than ever, considering our goals in the health and performance realms and our allostatic load is crucial. Appropriate stress dosing can be the difference between increasing capacity over time rather than issues such as burnout.
As always, it is the dose that makes the poison.
After having drafted this piece, I found this great illustration of allostatic load as it applies to most readers see below from Phil Learney (Co-Founder of HMN24):
References
McEwen, B. Allostasis and Allostatic Load: Implications for Neuropsychopharmacology. Neuropsychopharmacol 22, 108–124 (2000). https://doi.org/10.1016/S0893-133X(99)00129-3
Jenny Guidi, Marcella Lucente, Nicoletta Sonino, Giovanni A. Fava; Allostatic Load and Its Impact on Health: A Systematic Review. Psychother Psychosom 15 December 2020; 90 (1): 11–27. https://doi.org/10.1159/000510696
McEwen BS. Stressed or stressed out: what is the difference? J Psychiatry Neurosci. 2005 Sep;30(5):315-8. PMID: 16151535; PMCID: PMC1197275.
Word KR, Austin SH and Wingfield JC (2022) Allostasis revisited: A perception, variation, and risk framework. Front. Ecol. Evol. 10:954708. doi: 10.3389/fevo.2022.954708
Mann, J. Bryan1,2; Bryant, Kirk R.3; Johnstone, Brick3; Ivey, Patrick A.2; Sayers, Stephen P.1. Effect of Physical and Academic Stress on Illness and Injury in Division 1 College Football Players. Journal of Strength and Conditioning Research 30(1):p 20-25, January 2016. | DOI: 10.1519/JSC.0000000000001055
Calabrese, E.J., Mattson, M.P. How does hormesis impact biology, toxicology, and medicine?. npj Aging Mech Dis 3, 13 (2017). https://doi.org/10.1038/s41514-017-0013-z
Scheffer M, Bolhuis JE, Borsboom D, Buchman TG, Gijzel SMW, Goulson D, Kammenga JE, Kemp B, van de Leemput IA, Levin S, Martin CM, Melis RJF, van Nes EH, Romero LM, Olde Rikkert MGM. Quantifying resilience of humans and other animals. Proc Natl Acad Sci U S A. 2018 Nov 20;115(47):11883-11890. doi: 10.1073/pnas.1810630115. Epub 2018 Oct 29. PMID: 30373844; PMCID: PMC6255191.
Hard science translated v well. Bravo.