G.A.S (General Adaptive Syndrome) – broken down

When it comes to exercising and lifting weights the biggest mistake people make is that they rarely give a thought towards a rest and recovery day. The best time for to you grow is when you are actually sleeping, and not in the gym.

This is where the G.A.S (General Adaptive Syndrome) by Hans Selye comes in to play. Hans Selye was a pioneering Hungarian-Canadian Endocrinologist. He has done extensive work and is considered by many to be the first to demonstrate the existence of biological stress. Throughout his work he developed the three (3) stages of General Adaptive Syndrome.

Practical Programming Strength Training by Mark Rippetoe

General Adaptive Syndrome is a 3 stage process. Being an engineer my job is to reverse engineer how things work so I can fix them. During my studies for my NASM-CPT I covered the Endocrine system, and how the effects of exercise trigger certain responses in the body. This article was a great way for me to break it down and tie each component together with the hopes to understand it better.

Stage 1 -The Action Stage – (Known as the Fight or Flight response)

Let’s say someone is in the gym on the flat bench and they want to work on a new PR of  365 pounds for 1 rep. Let’s say for argument sake they have already warmed up with their initial 8-10 reps, and have already worked up to their last set for the max repetition. At this point the body has been put under a decent amount of stress which has caused some changes at a neuromuscular and cellular level. Eventually (ATP) – Adenosine_triphosphate levels will be lowered as the workout progresses. There will be a tipping point where the straw breaks the camels back (so to speak).  As the lifter prepares to lift the bar off of the rack with assistance from the spotter this will start the eccentric portion of the exercise by starting to lower the bar to their chest. At this point the body gets shocked due to the extreme load on the bar and CNS monitors and responds by trying to generate enough force to overcome the imposed demand as the weight comes down.

This is a moment of clarity when the lifter thinks to themselves “Oh <insert your expletive>, this is really heavy” and might even panic. This moment is when the fight or flight response kicks in.

Let’s actually analyze what is happening here.

  1. The lifter unracks the weight and starts to bring the weight down to chest level.
  2. The CNS (Central Nervous System) monitors the load via sensory receptors (afferent nerves), processes that information and responds via (efferent nerves). The result is the CNS & PNS working together to recruit all of the necessary forced-coupled muscle relationships in order to respond to the imposing load.
  3. This will trigger the HPA Axis (Hypothalamus, Pituitary Gland and Adrenal Glands) to become stimulated.
  4. The Hypothalamus upon simulation will signal the Adrenal Cortical System and will release CRF (Corticotropin Releasing Factor hormone).
  5. The Pituitary Gland (Anterior Lobe) will get signaled and will secrete the ACTH (Adenocorticotropic hormone). This will signal the Adrenal Glands to release the Cortisol steroid which is the main stress hormone.

  1. The Hypothalamus will also signal the (SNS) Sympathetic Nervous System and activate the Adrenal Medulla which release the Adrenaline and noradrenaline hormones.

Once this occurs the body will start to feel the physiological effects such as:

  • An increase in the heart rate and possible elevated blood pressure
  • An increase in (BGL) blood glucose levels
  • Increased blood flow to the muscles
  • Increased mental state of awareness
  • Increased muscle tension
  • Pupils can become dilated
  • The immune system may become suppressed by the elevated levels of cortisol and cortisone steroids release.

NOTE: Cortisol is the main stress hormone, and this is very catabolic to the body. If hormone levels do not return back to normal and stay elevated for prolong periods of time the body will feel the negative effects such as:

This is what is referred to as the action stage. Following this the body goes right in to stage 2.

Stage 2 – The Resistance  or Adaption Stage

Now that the stressor has been introduced, the body tries to protect itself by adapting to the load of the weight and stress being put on the muscular, skeletal, and metabolic systems. Clearly no one wants to drop 365 pounds on themselves and the body will have some sort of response. Once the repetition has been completed and the bar has been re-racked the only job now is for the body is to try to return to a normal state of homeostasis. This means reversing everything that just happened above and dropping blood pressure and levels, restoring breathing patterns, etc. Below is a visual to give you an idea of what this looks like.

See the source image

In the terms of working out if an individual keeps putting enough stress either via working out, work, etc these external stress factors will bring on these physiological changes. If one doesn’t allow for sufficient rest the bodies hormones are being forced to stay out of balance and they will enter stage 3. Over sessions of working out the Central Nervous System is processing all of this information and integrating it so when the next workout comes it will know how to respond appropriately. In short, this is where the body learns how to integrate what it just went through and adapts in which over each session the lifter will get stronger. In order to grow you need rest for recovery. This is a fine line and if one pushes too far and doesn’t listen to the bodies warnings signs (muscle soreness, DOMS, muscle inflammation, etc) they will start to work towards stage 3.

Stage 3 – The Exhaustion Stage 

Once a person has entered the Exhaustion stage the body can no longer keep up with the demands placed on it, and all of the bodies resources needed have been depleted. There are several things that will happen at this point that will have negative consequences.

  1. Injury – stressed or torn muscles from over stressing and lack of stretching to restore muscle lengths.
  2. Mental Depression
  3. Suppressed Blood Glucose Levels which results in reduced energy levels.
  4. Fatigue and possible chronic fatigue from over stressing the Adrenal Glands which keeps producing Cortisol.
  5. Blood Pressure levels can remain elevated

And lastly the most important and the entire reason you exercise is to make gains and get in shape. Make sure you take a break from time to time to treat your body that way it deserves to be treated!


  1. Wikiepedia.com
  2. NASM-CPT Study Guide
  3. Practical Programming Strength Training by Mark Rippetoe
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