Every Impact Is a Message: Stay Alive, Stay Strong, Stay in Motion

 By Thom Hartmann, Wisdom School

As Louise and I have aged (our 54th wedding anniversary is in two weeks), we’ve noticed that one of the biggest challenges is keeping our posture straight and our bones from getting brittle. There’s science behind this challenge, and it gives us all suggestions for “keeping young.” 

Bone is one of the few tissues in the human body that remains alive and dynamic from birth to death. It’s not the rigid, inert structure most people imagine when they think of skeletons. In fact, it’s constantly growing, dying, dissolving, and rebuilding itself through a delicate dance between two main kinds of cells—osteoblasts and osteoclasts. 

This balance is what keeps us upright, protects our organs, and allows our muscles to move us through life. But as we get older, the harmony between building and breaking begins to shift, and the results can be devastating. Understanding how that process happens—and how we might slow or reverse it—is one of the quiet frontiers of aging science.

Bone is built primarily by osteoblasts, the construction workers of our skeleton. They take raw materials—calcium, phosphate, and collagen—and create new bone matrix. This matrix starts out soft, like scaffolding, then mineralizes into the hard tissue we recognize as bone. Opposing them are osteoclasts, which act more like demolition crews. They dissolve old or damaged bone so it can be replaced. 

In a healthy adult, these two systems are in balance: every bit of bone that’s broken down is replaced by new bone. But that balance depends on a complex interplay of hormones, mechanical stress, and nutrients that becomes harder to maintain with age.

When we’re young, our bodies prioritize growth and repair. Hormones like growth hormone, estrogen, and testosterone all signal bone-building cells to stay active and reproduce. Even the act of moving—walking, climbing stairs, carrying groceries—tells our bones to stay strong. 

Osteoblasts thrive on impact; they literally sense mechanical stress and respond by building more bone where it’s needed. That’s why astronauts lose bone density in zero gravity and bedridden patients lose it quickly in immobilized limbs. Bones are designed for stress. They grow from it, adapt to it, and depend on it.

But aging quietly changes the equation. By the time most people reach their 40s or 50s, osteoblasts start slowing down while osteoclasts keep right on working. Estrogen and testosterone, which protect against bone loss, begin to drop. In women, the sharp decline in estrogen during menopause often leads to an acceleration of bone loss so dramatic it can reach one to two percent per year. 

The result is a net thinning of the bones that can culminate in osteopenia or osteoporosis. What’s more, osteoblasts themselves become less responsive to mechanical stress and less efficient at mineralizing new bone, while their numbers dwindle with each passing decade.

Yet, there’s another layer to this story that is both hopeful and cautionary. Bone cells are not fixed in number; they arise from progenitor cells—stem-like precursors in the bone marrow and periosteum (the thin tissue surrounding bones). These progenitor cells can, under the right conditions, become new osteoblasts. 

Exercise, especially high-impact weight-bearing exercise, stimulates their differentiation. Nutrients like vitamin D, calcium, and magnesium fuel the process. Even exposure to sunlight, through its effect on vitamin D synthesis, plays a critical role in signaling these cells to mature. In a very real sense, every step we take outdoors in the sunshine is a small act of bone regeneration.

On the other hand, disuse and a sedentary lifestyle send the opposite message. When bones aren’t stressed, the progenitor cells shift toward becoming fat cells instead of bone cells, and osteoclasts take over the stage. 

This explains why modern sedentary living, coupled with diets low in essential minerals, has created an epidemic of bone fragility even among people who think of themselves as healthy. 

It also explains why impact—whether from walking, jumping, or resistance training—isn’t just good for muscle tone; it’s a direct message to your bones to stay alive.

There’s a growing body of research exploring how bone regeneration might be enhanced as we age. Some of it focuses on pharmacological ways to stimulate osteoblast activity or block osteoclast overactivity, like the bisphosphonate drugs or parathyroid hormone analogs now used for osteoporosis. Others look at stem cell therapies that could replenish the aging pool of bone-forming cells. 

But many of the most effective tools we already possess are natural. Regular resistance training, adequate protein intake, and maintaining proper levels of vitamin D and K2 can have profound effects on bone density. The simple act of impact—bones striking the ground, muscles tugging on tendons, joints bearing weight—remains the single most powerful way to keep bones young.

The idea that bone “knows” when it’s being used and responds accordingly is one of nature’s most elegant feedback loops. It means that our skeleton is not a fixed thing but a living organ that senses and adapts to our behavior. 

When we stop moving, bones interpret it as a signal that they’re no longer needed and begin to fade away. When we challenge them, they thicken, harden, and renew themselves. Even in old age, this feedback loop can be reawakened, though the gains are slower and more fragile than in youth.

In the larger metaphor of life, bone regeneration is a quiet but powerful reminder of resilience. Every day, millions of microscopic breaks form in our skeleton, and every day they are healed. It’s a never-ending cycle of destruction and renewal that mirrors our emotional and spiritual lives. The same principle applies: stress and impact, handled well, make us stronger. Avoiding stress entirely—physical or emotional—leads to a kind of decay. Growth comes from the right kind of pressure.

So while supplements and science continue to explore the biochemical angles of bone regeneration, the most profound lesson may be a behavioral one. Move every day. Load your bones. Walk, climb, stretch, lift, push. 

Feel the impact of your feet on the ground, because your bones are listening. They respond to every signal of life you send them, even late into old age. They want to grow. They’re built to grow. But they require our participation—the literal weight of our will—to keep doing it. 

In the end, strong bones are not just the foundation of our physical structure but the embodiment of our relationship with gravity, effort, and resilience itself.

—Thom Hartmann, educator and commentator, is the author of many respected books. Reprinted with permission. To receive new posts you can become a free or paid subscriber of this reader-supported digital publication, The Wisdom School: What it Means to be Human, where all articles are free and available to everyone. Copyright: Thom Hartmann, 2025.