The SAID Principle Will Transform Your Fitness

The SAID principle stands for Specific Adaptations to Imposed Demands. It is THE fundamental concept in exercise science that explains how the human body responds and adapts to different types of physical stress.

There are two main parts to the SAID principle:
- Specific Adaptations: This means that the body will adapt specifically to the type of stress that is placed upon it. For example, if you want to improve your running endurance, you need to do activities that specifically target cardiovascular and muscular endurance.

- Imposed Demands: The adaptations are a result of the type and intensity of the stress placed on the body. If you challenge your muscles with resistance training, they will respond by becoming stronger. If you push yourself during cardio workouts, your cardiovascular system will improve.

Generally, we think of adaptations as falling within two categories: Structural and Neural.

Structural adaptations involve changes in tissue and muscle thickness or size. Neural adaptations involve your nervous system's ability to communicate and recruit your muscles -- a key capability for speed, power and strength.

This is all fine and well. But what are the practical implications for you?

1. If you don't use it, you lose it -- Spend all your exercise time running? Cool. Expect to see a loss in strength, power and mobility unless you invest in those as well. Spend all week lifting? It won't come as a surprise that you'll struggle on endurance events.

2. If you do the same thing all the time, it will gradually work less effectively -- if you squatted 2x/week, every week, and always loaded the same weight on the bar, within a few weeks your body will have adapted to that resistance and will no longer make the same improvements if any. The same applies to always running the same distance at the same pace, or knocking out 50 pushups every day.

The answer: a training program that comprehensively targets your goals (we recommend resistance + cardio), AND that progressively challenges you (which means loads, distances, speeds increase over time in a safe manner).

As long as you fuel and recover, your body will do what you ask it to do.