Allostasis and Physical Preparation
I just finished reading the book Allostasis, Homeostasis, and the Costs of Physiological Adaptation edited by Jay Schulkin. The book is fantastic and while it is not written specifically about physical preparation for sport the information contained inside has everything to do with physiological preparation for sport.
Homeostasis and Allostasis
Homestasis is a term most are familiar with and generally the word gets thrown around when we talk about training – “The goal of training is to disrupt homeostasis and force the body to adapt and get stronger.” There is, however, a difference between homeostasis and allostasis and understanding that difference may help us better understand the ramifications of our training program. While the authors who contributed chapters in Schulkin’s book all seem to agree there is a difference between homeostasis and allostasis they do have subtle differences in regard to how those terms are applied and the physiological processes they are applied to. Rather than getting so focused on those subtle differences I think that just grasping the basic concepts would be helpful before I try and put this into the context of physical preparation for sport.
The concept of homeostasis dates back to Walter Cannon’s work (1935) and for a broader understanding of Cannon’s work I suggest checking out his book, The Wisdom of the Body, as it is a classic in the field of physiology. Cannon used the term homeostasis to refer to the processes needed to preserve constant conditions within the body which are centered around specific set points and governed by negative feedback loops.
A common example of homeostasis often cited is the thermostat in your home. If you set the air conditioning to 80 degrees in the summertime the thermostat does not kick on until the temperature in your home rises above 80 degrees (the set point), providing negative feedback to the thermostat and requiring it to take action and regulate the temperature back to normal, achieving homeostasis. Of course, if you opened a window in the house the temperature would rise and be constantly above the set point of 80 degrees causing the theromstat to remain on for a significant period of time, as it attempts to maintain the homeostasis, until you finally either close the window or the thermostat breaks down because it has overworked itself.
One of the issues with the homeostasis model in health is that the medical community takes body set points very literally and thus we end up with a large number of medications being prescribed to help people maintain specific numbers considered to be “normal”. This issue was confronted by Sterling and Eyer in 1988 when their research led them to coin the term allostasis.
Allostasis, Allostatic State, & Allostatic Overload
Schulkin notes three distinguishable features of allostasis (pg. 7):
- Allostasis – The process by which an organism achieves internal viability through a bodily change of state
- Allostatic State – Chronic overactivation of regulatory systems and the alterations of body set points
- Allostatic Overload - The expression of pathophysiology by the chronic overactivation of regulating systems
Noted stress physiologist, Bruce McEwen, goes on to further differentiate between these features of allostasis and homeostasis by making the distinction that homeostasis applies only to a few physiological systems that are essential for life – pH levels, body temperature, and oxygen tension. These systems are so essential to human survival that slight fluctuations for a brief period of time could lead to death.
Thus, allostasis is not so much focused on constancy as homeostasis is, but rather, is able to fluctuate and alter set points in order to meet demands that are placed on the body. Additionally, rather than only being dependent on negative feedback loops, the allostasis model indicates that the body can be predictive and anticipate stress and react based on feed-forward information.
High blood pressure is a good example to use when trying to understand the difference between allostasis and homeostasis and how this has influenced the medical community, as I alluded to earlier. “Normal” blood pressure is often cited as being 120/80. If a patient presents at the doctors office with a blood pressure of 160/90 they are classified as being hypertensive and prescribed medication to try and bring their blood pressure back down to the “normal” 120/80. One of the issues with taking this homeostatic approach to blood pressure is that this individual’s blood pressure set point may have shifted for a reason. Perhaps they live an incredibly stressful life, they sleep only 4 hours a night, and they keep a poor diet. Their blood pressure is simply adjusting its set point in order to try and still be effective and get the job done. Prescribing medication means that you are not acknowledging all of those other important things going on with the individual’s health and well being and attempting to focus on the adaptation (allostatic state) that is rightfully taking place in the presence of these stressors rather than addressing the true problem – life stress, sleep, and diet. Additionally, the medication which is being used to treat their high blood pressure may do so at the consequence of other physiological systems, as there are often side effects and other systems need to adapt to the medication, placing these other systems into an allostatic state. Of course, if this allostatic state of high blood pressure goes on for a considerable period of time the individual may find themself in a state of allostatic overload – potentially life threatening.
Limitations of Selye’s General Adaptation Syndrome
Hans Selye, whom many consider to be the “Father of the Stress Response”, defined stress as a nonspecific response by the body to any demand whether it is pleasurable or non-pleasurable (eustress or distress). Selye broke stress down into three phases – alarm, resistance, and supercompensation:
The Alarm phase takes place when we encounter a stressor, causing the body to break down. The Resistance phase is our bodies attempt to combat this stressor in order to not only restore homeostasis but to actually put our body in a better position to resist that same stressor should it happen again, thus reaching a state of Supercompensation. Of course, if we continually breakdown and do not provide the body ample time or opportunity to resist the stress we are placing on it we reach a state of Exhaustion.
This model was revolutionary at the time as Selye literally discovered the stress response on accident by making some errors in his lab with the way he handled the mice he was studying. However, like most things, the picture is a bit incomplete and many stress physiologists look at adaptation in a different way. This stereotypical, non-specific response to all stressors, pleasurable or non-pleasurable, in no longer considered accurate. Rather, different situations and different stressors can mediate allostasis in different ways depending the response needed and the body’s ability to cope with the stress. Thus, there is a degree of specificity that stress has on the body and the perception that the body has to this stress will help to determine how it reacts.
Physical Preparation and Allostasis
Similar to the discussion regarding General Adaptation Syndrome, it is important to note that stress can have positive or negative outcomes depending on the amount of stress applied to the body and how the body adapts to that stress. While not discussed in the book, the term hormesis comes to mind. Hormesis is a term of biology used to explain how low levels of a toxin can produce a favorable biological adaptation to the cells while high levels of that same toxin would lead to cell death. This concept can apply to training, much like the model of allostasis discussed in the paragraph above, where a little bit of training can produce a favorable adaptation to the body – the appropriate amount allows the body to cope with the stress of the training session – but, if we push too hard and overload the individual they may achieve an allostastic state, where the biological systems become overactive as they attempt to adjust set points in response to the stress. If we then continually apply training stress we end up with a negative result and force the individual into allostatic overload – the toxin, in this case training, when applied at a low level led to favorable adaptations, however once we did too much it ended up becoming toxic and damaging to the system.
An allostatic state, where the body systems become overactive and adjust their set points in response to training stress, may not be such a bad thing. This would probably resemble a brief period of overreaching and, provided we monitor the athlete appropriately and do not push them over the edge, would lead to favorable gains as the increased set points for things like hormonal output, cardiovascular function, and central nervous system firing would result in the athlete getting stronger, faster, bigger, and more fit.
Thinking through this model of allostasis it makes me consider how training influences the three aspects of my Physiological Buffer Zone (which I discussed on the Strength In Motion DVD):
1. Good Movement
2. High Level of Stress Resistance or Stress Tolerance
3. High level of Fitness
All three aspects are governed by the same allostasis model and the amount of training that one can tolerate is highly individual. Some athletes need more focus in one area of the buffer zone than others and collectively, if we can raise each aspect as high as it possibly can be for the individual, we have a chance of developing someone that is highly resilient and able to tolerate a great amount of stress without breaking down. Essentially, their biological set points are higher and their body is able to anticipate stressors that may be applied to it – for example the psychological stress of game day, the physiological stress of the game, the stress of going into preseason where coaches usually run them into the ground, or the stress of travel from one competition to the next – and mount the appropriate stress response without becoming overactive and leading to potential allostatic overload and breakdown.
The Allostatic Model and Pain
As I read through the book I couldn’t help but think about the topic of pain when referencing this allostatic model. Pain is an output from the brain, a perception, based on all of the information coming in from the environment. When an individual suffers from chronic pain sometimes signals can get crossed and the person gets stuck in this state of protection where the brain is extremely hypervigilant and protective of the painful region. Thus, this individual finds themself first in an allostatic state where the system is hyperactive and set points – in this case perceptions of pain – are altered in order to initially protect the area from further potential damage. If this continues for a lengthy period of time the individual may then find themself in a state of allostatic overload where there is chronic overactivation of bodily systems that lead to a pathological state of chronic pain characterized by changes in the nervous system (central sensitization), changes in movement and motor programs, psychological changes (depression), and changes in behavior (fear avoidance).
The Allostatic Model and Hands on Therapies
Another place where it is interesting to consider this model is in various hands on or touch therapies (IE, massage and manual therapy). Touch may be one potential way in which we can help to influence the allostatic state and sort of “pull the person back” in an effort to preventing them from reaching a state of allostatic overload. Massage, when used appropriately, may help some cope with stress-related symptoms by decreasing anxiety and enhancing psychological well-being. Additionally, during periods of intense training or frequent competition (IE, the in season period) massage may be help to increase an athlete’s stress resistance and ability to cope with stressors when used at the right time during the week. This approach is essential during a long season to help maintain the health of the athlete and prevent them from breaking down and not being able to perform at their best during game time.
The allostasis model underpins everything that we do as strength coaches. Understanding this model can help us see the bigger picture when it comes to the training programs that we write and how different individuals may adapt to those programs. By understanding the unique ability of each athlete to adapt to the stress we place upon them we can begin to increase the athlete’s physiological buffer zone by increasing their biological set points and enhancing their bodies ability to be predictive and anticipate potential stressors.