Aspen Physical Therapist Explains How to Adapt to Altitude

The air in the Upper Roaring Fork Valley doesn’t just feel thinner; it feels like a physical weight lifting off your chest only to be replaced by a sudden, heavy fatigue in your lungs. You’re standing on a trailhead near Basalt or maybe just outside of Aspen, lacing up shoes that felt perfect at sea level, and suddenly, that familiar five-mile pace feels like a slog. The obvious reaction? Try harder. Push through the burn. Ignore the fact that your heart is hammering against your ribs like a trapped bird.

That’s the trap locals and visitors alike fall into every time the temperature drops and the altitude climbs above 7,000 feet. But according to Bill Fabrocini, a clinical specialist in orthopedic physical therapy at Ajax Fitness in Aspen, the answer isn’t brute force. It’s biology. And it’s a lot more complex than simply "trying harder."

"Everything is about oxygen. It’s living energy," Fabrocini said. He’s spent over 30 years coaching athletes and treating injuries, so he’s seen the difference between a runner who respects the altitude and one who fights it. The common misconception here is that there’s less oxygen in the air at high elevation. Not exactly. The percentage of oxygen stays the same, but the atmospheric pressure drops, meaning those oxygen molecules are spaced further apart. You inhale less of them with every breath.

This triggers a state called hypoxia — low oxygen levels in the body. In response, your kidneys release a hormone called erythropoietin, or EPO. This hormone tells your bone marrow to produce more red blood cells. Fabrocini puts it simply: "Think of red blood cells as buses. The oxygen is the passenger that goes on the bus, and the more buses you have carrying oxygen molecules, the better the transfer of oxygen."

It takes two to three weeks for that bus fleet to grow large enough to handle the load. During that window, your usual pace becomes a lie. If you try to maintain your lower-elevation speed, you’re essentially trying to run on empty. "If you’re just focusing on trying to match your pace, it can be a disastrous result," Fabrocini warned. "If you’re trying to run without as much oxygen utilization, you can run low on energy very quickly and burn out."

So, what do you do? You don’t just power through. You adapt. Fabrocini points to hydration — critical in our dry climate, and nutrition. You need iron-rich foods like red meat, spinach, and lentils to support that red blood cell production. You need carbohydrates for fuel and high-quality protein for recovery. And you need to watch the alcohol, which dehydrates you further.

Alex Olson, a local runner and member of the Roaring Fork Valley Tuesday Trails group, echoes this. He’s out there every week, feeling the same burn. "It’s important to slow it down and take it easy," Olson said. "Let your body tell you what it’s capable of."

It’s a simple instruction, but it’s one that gets ignored when you’re chasing a personal best or trying to impress a tourist crowd. The science is clear: your body is building a new transport system for your oxygen. It needs time. It needs rest. It needs the right fuel. If you ignore it, you don’t just get tired; you get injured.

Picture this: It’s 6:00 PM in early November. The sun is dipping behind the Elk Mountains, casting long shadows across the Roaring Fork River. A runner jogs past the local coffee shop, not at a sprint, but at a steady, conversational pace. They’re not slowing down because they’re weak. They’re slowing down because they’re smart. They know the buses are still being built, and they’re willing to wait for the fleet to arrive.