General Adaptation Syndrome: The Complete Guide

If you were to survey a group of people, the majority of the individuals would likely assert that stress is bad. After all, stress has been associated with a number of adverse physical and mental health consequences.

However, some amount of stress can be healthy, and even desirable, for the body. Your body has the ability to adapt to stress, which can lead to increases in strength and fitness, better stress and pain tolerance, etc. 

The physiological adaptations to stress have been described by general adaptation syndrome.

But, what is the general adaptation syndrome definition? What are the features of general adaptation syndrome? And what are the general adaptation syndrome stages?

In this article, we will discuss what general adaptation syndrome entails, the general adaptation syndrome definition, the general adaptation syndrome stages, and how to use the GAS psychology and physiology framework to manage stress appropriately in your own life.

We will cover the following: 

  • What Is General Adaptation Syndrome?
  • What Are the Stages of General Adaptation Syndrome?
  • Dealing With Stress

Let’s dive in! 

A notebook page that says general adaptation syndrome.

What Is General Adaptation Syndrome?

General adaptation syndrome (GAS) refers to a series of defined stages of physiological adaptations or changes your body goes through in response to chronically-applied stress. 

The stress attributable to GAS is often exercise training, but it’s also possible to see general adaptation syndrome in the context of other forms of physiological or even psychosocial stress.

We often think of various stresses, whether exercise training, financial stress, work stress, or chronic illness, occurring in some sort of a vacuum.

For example, if you are a distance runner, you might envision your training and workouts as only temporarily fatiguing your body within the 24-hour period surrounding the workout. 

Then, if you have a recovery day or rest day, or even a relatively easier run the next day, you might think that the body will immediately bounce back, and any result of the stress from training the day before will be all but erased.

A person stressed out at work with people pushing things in his face.

However, there’s an extensive body of research to show that chronic stress has numerous physical and mental sequelae that take place both during and potentially after the stress has resolved.

Stress mounts in the body, and the body adapts accordingly.

This isn’t to say that all stress is bad; in fact, you need the stress to trigger the positive physiological adaptations you are seeking through exercise training.

In this way, stress can be described as “positive stress“ or “negative stress.“

However, when the magnitude or duration of the stress exceeds your physical and mental capacity to respond and adapt quickly enough, or there is not enough rest and recovery to balance out the stress subjected to your body or brain, stress can induce deleterious effects.

A person stressed out at work with people pushing things in her face.

What Are the Stages of General Adaptation Syndrome?

As mentioned, the physiological changes that are seen with GAS psychology are typically described to occur in stages that play out in a predictable fashion.

The general adaptation stages were defined in the 1950s by Hans Selye, who first identified and named general adaptation syndrome in 1936. 

Upon further research and fleshing out of his GAS theory, Hans Selye added the GAS stages for a more concrete model of general adaptation syndrome.

The three stages of general adaptation syndrome are the Alarm Reaction stage, the Resistance stage, and the Exhaustion stage.

Let’s look more closely at each of these general adaptation syndrome stages:

People working out on rowing machines.

#1: Alarm Reaction Stage 

The first GAS stage is called the Alarm Reaction stage. This stage involves your body‘s initial response to a stressor.

When the body encounters some type of physical or psycho-social stress, the sympathetic nervous system is activated. This is the “fight-or-flight” branch of the autonomic nervous system designed to help your body handle some type of perceived threat. 

Even “positive stress“ is a perceived threat to the body. 

For example, a good run or a vigorous workout will activate the sympathetic nervous system as you are putting your body under physiological stress relative to rest. 

When the sympathetic nervous system is activated, it triggers various physiological responses, one of which is stimulating the adrenal glands to secrete hormones such as epinephrine (adrenaline) and norepinephrine.

These hormones set off a cascade of reactions in your body, such as an increase in your heart rate and breathing rate, an increase in blood pressure, and heightened attention.

Thus, the alarm reaction stage of the general adaptation syndrome is evidenced by physical symptoms such as elevated heart rate, dilated pupils, faster breathing rate, flushed skin, trembling or muscle twitching, and heightened senses.

According to the general adaptation syndrome model, these symptoms disappear during GAS stage two but reappear in the final GAS stage.

A person exhausted from working out.

#2: Resistance Stage

After the initial “alarm bells“ go off when your body is keyed into stress, your body tries to repair itself from the shock or stress that has occurred. This is the resistance stage of GAS.

As long as the stress was acute, the resistance stage will see all of the physical symptoms of the sympathetic nervous system activation revert back to homeostasis.

However, if the stress persists, the sympathetic nervous system will remain active, which will continue to elevate blood pressure because the same stimulating hormones are being released. 

Your body will continue to fight to restore homeostasis by continuing to “fight or flight“ distress until it is gone.

However, prolonged chronic stress will begin to manifest as other symptoms such as headaches, difficulty sleeping, anxiety or depression, chronic fatigue, etc. 

Additionally, prolonged stress will lead to chronic elevation of cortisol, the primary stress hormone.

There are various consequences of high cortisol levels.

For example, there are several chronic illnesses that have been shown to be associated with chronically elevated cortisol. High cortisol levels can increase the risk of hypertension, type 2 diabetes, heart disease, osteoporosis, and obesity.

A person hunched over, exhausted.

Numerous research studies have shown an association between high cortisol levels and weight gain, particularly in the abdominal region.

Moreover, if your body continues to fight unresolved stress and cortisol remains elevated, you can experience difficulty sleeping. This can lead to lethargy and lack of energy, which will further compromise your physical, mental, and emotional ability to deal with stress.

Ultimately, according to the theory of general adaptation syndrome, if the stress persists too long or your “resources“ or your body‘s ability to continue to mount a “resistance to the stress,” you will enter the final general adaptation syndrome stage.

#3: Exhaustion Stage

The exhaustion stage of general adaptation syndrome occurs when your body and mind are drained to the point that you no longer have adequate physical, mental, and emotional resources to fight the persistent stress.

According to research, symptoms of the exhaustion stage of GAS include overwhelming fatigue, physical or mental burnout, reduced stress tolerance, depressed immunity, insomnia, and an increased risk of chronic diseases such as heart disease, hypertension, type 2 diabetes, depression, and anxiety.

A person meditating outside.

Dealing With Stress

The best way to prevent escalating through the stages of the general adaptation syndrome model is to support your physical, emotional, and mental recovery from acute stress.

Even positive stress, termed eustress, requires sufficient rest and recovery, such as a rest day after a high-intensity workout or a nutritious meal and warm shower after shivering in the cold and rain at your child’s soccer game for hours.

When you are going to be under more chronic stress, such as changing jobs or moving to a new home, it is important to incorporate stress-reducing activities such as daily exercise, meditation, yoga or tai chi, a nutritious diet, and getting plenty of sleep. 

It’s important to keep in mind that although regular exercise can help improve stress tolerance and reduce stress, excessive exercise with insufficient recovery will lead to overtraining.

Studies have found that when you are training too intensely and not giving your body adequate rest and recovery, levels of cortisol rise significantly, and you will increase the risk of hitting the exhaustion stage of the general adaptation syndrome.

A person meditating in their room.

If you are feeling depleted or tired from your exercise routine, and it seems like recovery isn’t as fast or complete as it was previously, it is likely a sign that you need extra rest or a sign of high cortisol.

You should take days off until you are feeling better and then readjust your training moving forward to include more rest days per week.

If you have concerns about your ability to manage stress, you should speak with your healthcare provider or a licensed therapist.

For more information about how to reduce stress in your body, check out our guide for decreasing cortisol levels here.

The word cortisol written on a notepad.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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