The Three Unbreakable Laws of Healing: A First Principles Approach to Physical Therapy
- Dr. W Zach Smith
- 6 hours ago
- 5 min read
If you ask five different professionals how to fix knee pain, you might get five different answers. One says rest and ice. Another says squats. A third says your glutes are asleep, a fourth blames your posture, and a fifth wants to stick needles in you.
It’s confusing. It feels like guesswork.
Why is there so much conflicting advice in rehabilitation? Because most healthcare operates on reasoning by analogy. We do things because “that’s how it’s always been done,” or because "it worked for the last guy." We rely on methods, trends, and traditions.
But what if we stripped all that away?
Inspired by thinkers like Aristotle and Elon Musk, First Principles Thinking requires us to boil a subject down to its fundamental, irrefutable truths. The things that cannot be deduced from anything else and cannot be easily falsified by science. From that bedrock foundation, we build upward.
When we apply a rigorous scientific audit to Physical Therapy, we find that many cherished beliefs (like "perfect posture" prevents pain, or that everything is connected via a "kinetic chain") are actually just helpful rules of thumb that are sometimes wrong.
When you strip away the heuristics, you are left with only three irreducible laws of biological rehabilitation.
Here is physical therapy rebuilt from scratch, using only first principles.
The Difference Between Principles and Methods
Before we dive in, we must distinguish the foundation from the house.
A First Principle is a fundamental axiom of nature (biology or physics). It is true regardless of context. Gravity is a first principle. You cannot "hack" gravity.
A Method or Strategy is a tactic used to navigate those principles. Building an airplane, a ladder, or a parachute are all different methods of dealing with the principle of gravity.
In rehab, we often confuse the two. We think "Deadlifts" are a principle. They are not. The deadlift is just one method to apply force to the body.
If you understand the principles, you can invent your own methods. If you only know methods, you are stuck when the situation changes.
Here are the three unbreakable laws that govern all rehabilitation.
Law #1: The Principle of Tissue Tolerance (The Physics)
The First Principle: Structural failure occurs when the Applied Load > Tissue Capacity.
This is simple Newtonian physics applied to biology. Why does a bridge collapse? Because the weight of the trucks drove more force into the steel beams than the beams had the structural integrity to handle.
Why did your Achilles tendon snap? Not because you have "bad mechanics" or the wrong shoes. Those might contribute to the load, but the fundamental cause is that the force of your jump exceeded the tensile strength of your tendon at that exact moment.
The Analogy: The Body’s Bank Account
Think of every tissue in your body (muscle, bone, tendon) as having a bank account balance representing its "Capacity."
Sitting on the couch costs $1.
Walking up stairs costs $10.
Sprinting costs $100.
If your Achilles tendon currently has a balance of $150 (its capacity), and you go for a hard run that costs $200 (the load), you go into debt. In biology, "debt" means tissue failure, micro-tearing, and injury.
The Implication: To heal, you only have two levers. You must either reduce the spending (lower the load) or increase the bank balance (increase capacity). You cannot "correct" an injury with alignment if the math of Load > Capacity doesn't add up.
Law #2: The Principle of Biological Adaptation (The Mechanism)
The First Principle: Living tissue remodels its structure based strictly on the specific mechanical forces applied to it.
This is what separates a human leg from a table leg. If you repeatedly put heavy weights on a table, the table leg weakens over time.
But human tissue is "antifragile." It doesn't just resist stress; it requires stress to maintain its structure. This is known in biology as the SAID principle (Specific Adaptation to Imposed Demands) and is driven by a cellular process called mechanotransduction. Cells sense physical force and turn it into chemical signals to build new tissue.
The Analogy: The Callus
How do you get a callus on your hand?
You don't get it by resting your hand in a bucket of ice. You don't get it by wishing for it. You get it by applying friction (mechanical stress) to the skin.
If the friction is too intense, you get a blister (See Law #1: Load > Capacity). But if the friction is just right—challenging but not overwhelming—the skin cells react by laying down thicker, tougher protein layers.
The Implication: This is where traditional "rest and ice" advice often fails. Rest is necessary for the initial acute phase of healing to let the "blister" calm down. But rest never builds a callus.
Passive treatments—massage, ultrasound, heat, ice—cannot strengthen tissue because they do not provide the mechanical signal required for cellular remodeling. Only movement and load are medicine for building capacity.
Law #3: The Principle of Neuroplasticity (The Software)
The First Principle: The relationship between tissue status (input) and pain/movement (output) is modifiable by the nervous system.
Modern neuroscience has proven definitively that tissue damage $\neq$ pain. You can have terrible-looking MRIs with no pain, and you can have excruciating chronic pain long after the physical tissue has completely healed.
Pain is not a direct gauge of damage; it is an output of the brain based on its perception of threat. The nervous system can learn to be sensitive, and it can learn to be calm.
The Analogy: The Smoke Detector
Your nervous system has a built-in smoke detector designed to protect you. When you acute injure yourself (like spraining an ankle), there is a real fire, and the alarm screams (pain).
However, in chronic pain, the hardware (the tissue) might be healed, but the software is corrupted. The smoke detector has become hypersensitive. Now, it screams when you just burn toast, or even when you just turn the oven on.
The Implication: If you are treating a patient with chronic pain by only looking at their tissues (Laws #1 and #2), you are trying to put out a non-existent fire instead of fixing the faulty alarm system. Rehabilitation here requires "desensitizing" the nervous system through graded exposure to movement, proving to the brain that movement is safe.
Putting It Together: Principles vs. Methods
Once you understand these three laws, the confusing world of physical therapy methods becomes clear. You realize there are no "magic" exercises, only methods that either respect or violate these principles.
Here is how common methods map to the true fundamental principles:
The Method/Strategy | Which First Principle is it using? | Why it works (or doesn't) |
Crutches / Braces | Law #1: Tissue Tolerance | It temporarily reduces the "Load" side of the equation so it doesn't exceed current capacity. |
Heavy Resistance Training (Squats/Deadlifts) | Law #2: Adaptation | It provides a high-magnitude mechanical signal to bone and muscle cells, forcing them to build thicker structures. |
Slow, Progressive Tendon Loading | Law #2: Adaptation | Tendons hate sudden changes. Slow loading is the specific language tendon cells need to reorganize collagen. |
Pain Neuroscience Education (Talk Therapy) | Law #3: Neuroplasticity | By understanding that pain doesn't equal harm, the patient reduces fear, which recalibrates the "smoke detector." |
Ice / Heat / Massage | NONE (Mostly) |
Conclusion
If you are injured, stop looking for the "best exercise" or the newest gadget. Instead, look at your situation through the lens of these three unbreakable laws.
Are you asking your body to spend money it doesn't have? (Manage the Load)
Are you providing the right mechanical signal to tell your body to build armor? (Apply Specific Force)
Is your alarm system reacting to a fire that burned out months ago? (Retrain the Brain)
Rehabilitation is not magic. It’s just applied physics and biology.
