The SAID Principle Always Applies

The SAID principle is an old acronym from the strength and conditioning world that many professionals refer to with a knowing nod. I’m not sure who first came up with the adage, but some attribute it to the great Franklin Henry back in 1958 so, it’s not new. The beauty of it is in its simplicity: “Specific Adaptation to Imposed Demand” (SAID). It is self-explanatory, but essentially it says that the body will adapt specifically to the demands placed upon it.

Now, like most good and simple foundational concepts, this falls under the heading of “No duh”. Other related ideas that also fall under the same heading include the fact that time and recovery are factors here as well. In other words, if you throw too much demand too fast and too intense, you’re doing it wrong.

The funny thing about the SAID principle is how quickly health care providers seem to forget about it when dealing with athletes.


First let’s talk about the limitations of the principle. I think the biggest one is that the demand required for adaptation seems to be logarithmic and therefore non-linear. I know those are some big words for such a little guy, but it just says that change gets a lot harder as you get further along. An example of this would be the quick adaptations that are achieved when starting an exercise program (going from 65lbs deadlift max to 135lbs deadlift max), contrasted with the slow adaptations (GAINZ) that come after years of training (going from 495lbs deadlift max to 505lbs deadlift max). Again, this falls under “No duh”.

And there is a limit to the ability to progress. I’m not going so far as to say that there is a true ceiling to the adaptations achievable, world records continue to get broken, but I do think that there is a functional ceiling that is determined by genetics, age, health, etc. When close to that ceiling, the amount of work and time that it would take to make even incremental change is just not realistic. It’s not that I could never lift 600lbs, it is that I only have so much time, effort, desire, etc. to devote to such endeavors. If my genetics require 32 hours a day of work to get to a 600lbs lift, then it has entered the realm of absolutely impossible. So yeah, there are limits.

Applying to athletic injuries

Something that I see way too often in managing orthopedic injuries in athletes is this idea of resting an injured area until it “heals”. I think too many providers miss the absurdity of this way of thinking about managing an injury. It actually completely fails to consider the SAID principle.

Now let’s stop for a minute because I have the feeling that you are already misunderstanding me. You are probably thinking “Yeah I know, we need to load an injury for it to heal. Load is treatment.” Not exactly. The first thing I need to do is get this idea of “healing” out of your head. The principle is the “specific adaptation to imposed demand” – Not “specific healing to imposed treatment”.

It’s the SAID principle, not the SHIT principle.

People often think of “healing” as the injured part restoring to what it was before the injury. What we actually need is for the injured area to adapt to something that is functionally able to handle force – we actually don’t care if it “heals” but if it can handle the required loads of sport without getting pissed off (it is common for an old injury to still show up on MRI with no residual deficits). Rest alone won’t achieve that.

I know what you are thinking. “But Erik, we have patients rest in the early days after surgery for the initial phase of healing – and it works.” I want you to think about that differently.

First, surgery (or any acute injury) is one huge demand that will cause its own adaptive process. Let’s think less of that process as “healing” the area and more of it as “adapting to its new normal”. The early days after such an event is the time when that initial adaptation is occurring as a response to that initial demand. The inflammatory process helps drive adaptations. Things are so tenuous right after a serious injury that it is very easy to overload and damage the area, so pain comes in to keep you from doing too much too fast. As long as you rest it, the area will calm down and finish that initial adaptation, but the body has not yet received any feedback for how much more adaptation needs to occur.

Remember that logarithmic thing that goes on with the SAID principle? After the initial adaptation to the injury itself, the initial amount of demand required to drive continued adaptation is tiny. Even if you have the area completely immobilized and non-weight bearing, the little wiggles inside the brace are plenty of demand to drive early additional adaptation to more load. The rest is allowing that adaptation, not driving it.

Let me state that again more clearly:

Rest allows early adaptation, but neither causes nor drives it

And here is where our view of this process goes off the rails. We think that the rest is causing the adaptation (“healing”) and more rest will cause more “healing”. They may even look to an MRI to see if it looks pretty in there and therefore “healed”. All this rest will do is allow the inflammatory process to settle down as those initial adaptations conclude, and it will “feel strong”. At least until it gets overloaded again. And that is something I see all the time. They rested the athlete until it didn’t hurt anymore, then put them back to sport only to get “reinjured”. They forgot that it goes demand-adaptation-demand-adaptation-demand-adaptation-and so on. It’s a continuous process.

Some providers accidentally do get them back successfully. After it “healed” with rest the athlete does a gradual return to sport, achieving those more advanced adaptations through simple graded activity – which is great! Or, unfortunately, often times they just allowed the athlete the time to figure out strategies to stress shield that area until they are presented with a specific sporting situation and blammo – which is a conversation for another post.

Be purposeful

In my opinion, this works very well for the general population just trying to get back to basic activity (we tend to overtreat these people). “Once it calms down, gradually get back to your activities and let me know if you are having any issues.” But for athletes returning to higher level sport (or general population that needs more help), I think the better way to do this would be to target the injured area as soon as possible with a force gauge (dynamometer, force plate, etc.) to see how much adaptation has taken place – and still needs to go. Then deliberately apply the appropriate demands to drive the desired adaptation. You know, load it. Purposefully. And measure that change.

You see, the SAID principle is always at play. It applies during conditioning for injury prevention. It applies at the moment of injury. And it continues to apply all the way to return to play. There is no “healing phase” and “loading phase”.

It’s just SAID.


In summary…

  • Specific Adaptation to Imposed Demand (SAID) is always going on
  • Demand required for adaptation is logarithmic
  • It’s the SAID principle not the SHIT principle
  • Rest allows early adaptation, but neither causes nor drives it
  • Be purposeful