Module 2: Why Impact Matters
This is a very important module to understand and it lays the foundation for what follows.
If Module 1 challenged the idea that the human body is inherently fragile, today’s module takes that idea one step further. It examines one of the most misunderstood, avoided, and biologically necessary forms of stress: impact.
ICYMI:
Our first Module
Module 1: You Are Not Fragile
These modules are designed to help people build fitness, resilience, and long-term capacity. Strength, aerobic health, impact, and intensity all matter, and we will cover them all. But decades of clinical experience have taught me that outcomes are often decided long before any formal training ever begins—by beliefs.
I was a guest on the Science of Maximal Athletic Development Podcast the other day. I joined both Alan Couzens and Iñaki de la Parra. I was honored to be their guest. This was a great conversation about healthspan and longevity in the athletic development space. Enjoy.
For many people, impact has become synonymous with danger. Jumping is risky. Running is harmful. Landing is something to avoid. Even the word itself—impact—carries a sense of threat. And so, as people age, they are often advised to remove it entirely from their lives, as if it were an optional feature rather than a foundational one.
But that framing is not neutral. It changes how people move, how they train, and what their tissues are ever asked to tolerate.
Impact is not just a mechanical event. It is truly a fundamentally necessary biological signal.
It tells bones how dense they need to be.
It tells tendons how stiff and elastic they must become.
It tells muscles how quickly they must generate force.
It tells the nervous system how to coordinate and stabilize under load.
When that signal disappears, those systems do not remain unchanged. They adapt downward.
What impact really is
Impact is not simply “hard landings” or “dangerous forces.” It is any rapid exchange of force between the body and the ground or an external object. It occurs when you step off a curb, descend stairs, catch yourself from a stumble, or change direction quickly. These are not athletic acts. They are acts of daily living. And you require training to withstand and tolerate these forces.
What makes them feel dangerous is not the presence of impact itself, but the absence of preparation for it!!
In physics, force is a product of mass and acceleration. In biology, force becomes meaningful only in relation to the tissue’s capacity to tolerate it. A force that is trivial for one person may be injurious for another—not because the force is inherently dangerous, but because the system receiving it is underprepared.
This is the part that is often missed. And this is a source of fear for far too many.
Risk is not absolute. It is relative.
A low-capacity system experiences everyday forces as high-stress events. A higher-capacity system experiences the same forces as a routine one. The difference is not bravery. It is biology.
Why bones, tendons, and cartilage need impact
Bone is not static. It is a metabolically active tissue that responds to mechanical strain. When exposed to dynamic loading—particularly loading that includes rapid changes in force—bone increases its mineral density and improves its structural architecture. This is why impact has such a strong effect on skeletal health, particularly in relation to osteoporosis and fracture risk.
When that loading disappears, bone does not maintain its structure out of loyalty. It downregulates. It becomes lighter, less dense, and less able to withstand force.
Tendons behave similarly. They are not just passive ropes connecting muscle to bone. They are viscoelastic tissues designed to store and release energy. That property—elasticity—is built and maintained through dynamic loading. Without it, tendons become “stiffer”, less tolerant of rapid force, and more vulnerable to injury when those forces inevitably appear.
Cartilage, too, depends on movement and cyclical loading to maintain its health. It has no direct blood supply. Its nutrition comes from compression and decompression, which drive fluid exchange. Removing dynamic load does not protect cartilage. It deprives it.
These systems do not deteriorate because people age. They deteriorate because they are underused.
Age modifies the rate of adaptation, not its existence. Yes, we adapt more slowly.
