The Principles of Adaptation
17 Oct

The Principles of Adaptation


“What doesn’t kill you makes you stronger”—or in the eyes of strength and conditioning coaches around the world, specific adaptations result from imposed demand, also known as the SAID principle.

The SAID principle (specific adaptation to imposed demand) explains that when the body is placed under any form of stress, it starts to make adaptations that allow the body to improve at withstanding that specific form of stress in the future. This even explains the massive benefits of continual sauna and cold water exposure. The acute stress causes the body to adapt, thus responding in a way that promotes many health benefits ranging from increased cardiovascular health to strong immune function and more.


Regarding resistance training, the mechanical stress of lifting external loads will cause a specific stress on tendons and ligaments, causing them to thicken and strengthen. But in order for the body to respond and adapt, it’s important to ensure that the right amount of stress is elicited and that there is enough specificity to ensure carryover. There is a huge difference between showing up to work out and just “moving,” versus training in a way that elicits a purposeful stressor that causes a metabolic or hypertrophic response.

Although this principle can be used with any sport or skill from soccer to piano and motor learning, let’s stick to adaptations specifically in regard to resistance training to build muscle (hypertrophy) and/or improve strength.

Chris Beardsley explains the perfect dose response in order to utilize the SAID principle and adapt to a resistance training program.

“Muscle growth is not determined by the degree of motor unit recruitment,

but by the mechanical loading experience of each muscle fiber.

To achieve the necessary level of mechanical loading, contraction velocity

must be both maximal and slow, because only this combination

leads to enough simultaneous cross bridges forming

in the muscle fibers controlled by high-threshold motor units.

This state can be achieved by either (1) lifting heavy weights or

(2) lifting light weights to muscular failure.”

Sure, anyone can lift weights but if the specific dose response is not elicited, there will not be enough stress to the ligaments and tendons of the muscle to create an adaptation. And the desired adaptation will depend on the type of stress placed upon the musculoskeletal system.

In other words, it’s less about the amount of muscle fibers that are recruited during a single lift and more about the amount of stress imposed on each muscle fiber. For example, the trap bar deadlift is a great multi-joint exercise that utilizes every muscle of the posterior chain including the hamstrings, spinal erectors, traps and posterior delts, etc; but if the movement is not conducted in a way that recruits high-threshold motor units, there will not be an adequate amount of stress to create adaptation. For those looking for strength adaptations, lifting around 80% or higher of your max is necessary with an intent of using progressive overload week-to-week in order to continue applying stress to the system. Whereas, for those looking for a hypertrophic response in the body, lifting lighter weights to maximal contraction will be sufficient. More simply put, if it feels easy, your body is most likely not in a state to elicit an adaptation.

The SAID principle (again, specific adaptation to imposed demand) is not confined solely to biomechanical adaptations. Even as someone learns physical skills through repeated practice, there are actually physical changes to the structure of the brain. Therefore as it relates to skills, if you want to get better you need to expose yourself to that particular skill frequently, and specificity is extremely important to consider. It doesn’t matter how bad you want to improve your double-unders or handstand walks; if you don’t spend adequate time practicing, you will not get better. And, as it relates to more specific goals such as improvements in rock climbing, water skiing, gymnastics, etc - specialized strength training will be beneficial to some degree but more importantly, getting on the rocks, in the water and on the gymnastics floor to practice is where the greatest adaptations will be made.

If you feel stuck in your ability to adapt and are looking for a more progressive and personalized training plan that supports your health and fitness goals, schedule a free strategy session with a Central Athlete coach today to learn how Central Athlete utilizes a holistic approach to ensure you move objectively towards your unique goals.



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