Fitness Education: The GAS Principle

When creating your own exercise or workout program, you first have to think about your SMART goals then you have to apply the FITT Principle. When thinking about the longevity of your plan and how you want to progress, you now have to apply the GAS Principle.

GAS stands for General Adaptation Syndrome. Coined by a Canadian endocrinologist, Hans Selye, when applied to human physiology, the concept of GAS is it is the body’s response to a new stimulus (such as physical stress). Stress causes the body to reduce performance, however, the body reacts to adapt to the new stress it has been introduced to, leading to increased performance, muscle adaptation, etc.

The General Adaptation Phase has 3 phases

Alarm (or Shock) Phase

The phase where new stress/stimulus/change has been introduced to the body (examples: increase resistance, heavier weight, faster speed, longer distances, lower recovery times, etc.).

It May last several days to several weeks.

Excessive soreness, excessive stiffness, and decreased performance can be expected.

Resistance (or Overcompensation) Phase

The phase where the body begins to biologically change (changes include: neurological, muscle tissue, biochemical, structural, and mechanical adaptations) to adapt to new stimuli.

It may also last several days to several weeks.

The body returns to normal function and increased performance.

Exhaustion Phase

The phase that must be avoided when signs and symptoms arise. If the stimulus continues to be applied, the negative effects of the exhaustion phase begin excessive soreness, excessive stiffness, decreased performance, irritability, excessive tiredness, other  symptoms of “overtraining.” These symptoms are the same negative symptoms as described in the Alarm Phase, however, the body is unable to continue to adapt.

Risk of injury during this phase increases.

Keys to understanding General Adaptation Syndrome

Stay consistent – the Alarm phase can last up to several weeks and can easily cause frustration and discouragement when starting a new program. Understand that the first few weeks are difficult, but that the consistency will eventually be rewarded. Continue the program and if you are still not seeing results within 4-5 weeks, then it may be time for a change.

Stay cognizant – be aware of how you are feeling; you will feel those negative effects but should also see positive results. If you are not seeing the results you wanted, take a step back and reevaluate the program or speak with a professional on how you can tweak or change your program based on your needs and goals.

Avoid injury – listen to your body and learn the symptoms of the Exhaustion Phase and of Overtraining. If you have pain: stop and consult with your doctor. Adaptations do not come without change, but you have to be careful about how and what you are changing and stressing. Avoid Exhaustion and Overtraining to greatly reduce your risk of reinjury.

If you have any questions about the GAS Principle or would like to speak with a member from Home Base’s Warrior Health & Fitness team, click here or call 617-724-5202 to speak with a team member directly.


1.Essentials of Strength Training and Conditioning Third Edition by Baechle and Earle
2. The National Strength and Conditioning Association’s (NSCA) Basics of Strength and Conditioning Manual by Sands, Wurth, and Hewit

About the Author: Christopher is an Athletic Trainer and a Certified Strength and Conditioning Specialist with Home Base’s Warrior Health and Fitness Program. He joins Home Base after spending the past two years as an athletic trainer at Long Island University Brooklyn, working with the school’s NCAA Division-I Men’s Soccer and Men’s and Women’s Track and Field teams. Additionally, to fully understand the physical and mental challenges the “tactical athlete” faces, Christopher joined the Garden City Fire Department on Long Island, NY with the added benefit of serving his local community. The San Diego, CA native is a member of the National Athletic Trainers’ Association, National Strength and Conditioning Association, Armed Forces Athletic Trainers’ Society, and Public Safety Athletic Trainers’ Society. Manzano is a board-certified athletic trainer, certified strength and conditioning specialist, and tactical strength and conditioning facilitator.