I was sitting in a sauna in Helsinki when the master told me to stop. Not the typical sit-and-relax sauna. This was the old kind — löyly, the steam that hits you when you pour water on the rocks and the temperature jumps to 100 degrees Celsius. I’d been inside for about five minutes. My skin was flushing. My breathing had shifted into something controlled, almost rhythmic. He told me to step outside into the cold. Minus fifteen degrees. I walked into the snow barefoot.
What happened next was not metaphorical. My core temperature didn’t drop. It climbed. My body began generating heat in a way I could feel distinctly in my chest and torso. My breathing had automatically shifted to something even more controlled. I was shivering, but underneath the shiver was something that felt like internal combustion.
That’s tapas. That’s what five thousand years of Vedic texts are describing.
What the yogis were actually documenting
The Sanskrit word tapas means heat. Fire. Not poetically. Physiologically. The ancient practitioners observed that if you expose your body to controlled thermal stress — alternating heat and cold, or sustained intensity in a posture, or specific breathing patterns — something activates inside you. A kind of internal fire that produces heat, strengthens the nervous system, clarifies the mind, and builds the capacity to sustain attention. They refined the protocol over centuries. They documented what conditions ignite this fire and what extinguishes it.
The Vedic texts describe tapas as generated through specific practices: pranayama (breath control that forces your system to adapt to lower oxygen and higher carbon dioxide), held postures at the edge of physical capacity, fasting that forces your metabolism to switch sources, heat exposure, cold exposure. The texts also describe what happens if the fire burns too hot — depletion, burnout, nervous system breakdown. Or if it burns too low — stagnation, lethargy, the capacity to practice dissolving. You need the right temperature.
This is diagnostic language. Not poetry.
When I teach students and watch who progresses, it’s always the ones who’ve addressed their tapas first. The ones who breathe deliberately. Who expose themselves to temperature stress regularly. Who are disciplined with food and fasting. Who push their bodies to genuine effort. Those students’ minds stabilize faster. Their meditation deepens. Their capacity to work with trauma and integration expands. It’s not mysterious. It’s mechanical. Their cellular engine is finally working.
The cellular machinery: mitochondrial hormesis
Mitochondria are the power plants in every cell. They produce ATP through a process called oxidative phosphorylation. Your physical endurance, your mental clarity, your resilience in stress, your capacity to adapt — all of these depend on how many mitochondria you have and how efficiently they function.
Here’s what matters: mitochondria respond to a very specific kind of stress by multiplying and strengthening.
When you expose yourself to controlled challenge — your breath restricted, your body temperature elevated, your muscle tissue demanding more oxygen than you’re getting, your body forced to fast — your cells interpret this as survivable pressure. They don’t interpret it as damage. They interpret it as a signal to build more energy-producing capacity. This is called hormetic stress. Hormesis. The stimulus is real. The challenge is genuine. But your system survives it and adapts by building a stronger mitochondrial network.
This is why people who regularly expose themselves to heat, cold, breathwork, and fasting have significantly higher mitochondrial density than people who avoid these stresses. It’s measurable. You can track it.
The Vedic tapas practices activate this response. Every single one of them. Pranayama increases carbon dioxide tolerance and forces hypoxic adaptation. Held postures create sustained ATP demand that forces mitochondria to proliferate. Fasting switches your metabolism from glucose oxidation to fat oxidation — a metabolic state that strengthens the mitochondrial system. Heat exposure triggers heat shock protein cascades that repair and reinforce mitochondrial proteins. Cold exposure activates brown fat and stimulates mitochondrial biogenesis. The classical yoga sequences cycle the nervous system between intense sympathetic activation and deep parasympathetic recovery. This cycling is exactly the pattern that optimizes mitochondrial function.
Five thousand years before mitochondrial biology existed as a field, the Vedic tradition had encoded a precise protocol for strengthening the exact cellular machinery that modern research is now validating.
What the data shows
I don’t expect you to take this on my word. The evidence is worth attention.
Chris Palmer is a psychiatrist at Harvard Medical School. He’s spent the last decade documenting that psychiatric disorders — depression, bipolar disorder, schizophrenia, anxiety, PTSD — correlate not just with neurotransmitter dysfunction but with mitochondrial dysfunction. When mitochondria fail, the brain starves for energy. Mental illness is a symptom of cellular starvation.
What’s remarkable: when he restores mitochondrial function through dietary intervention — particularly protocols that force fat oxidation — patients who’ve been resistant to pharmaceutical treatment for decades sometimes recover completely. Full recovery. Return to baseline.
Bessel van der Kolk documented how trauma disrupts cellular energy regulation. Trauma locks the body in a stress response that systematically depletes mitochondrial function. This is why talk therapy alone often fails for PTSD. You cannot verbally convince a cell to function.
Michael Levin at Tufts discovered that bioelectric patterns — the electrical communication between cells — guide development and regeneration in ways that mirror what the Vedic texts called prana: the vital force flowing through specific channels, carrying information and energy.
And Bernardo Kastrup argues from analytical idealism that consciousness is not produced by the brain but is fundamental to the fabric of reality. If that’s true, then the cellular fire is not just fuel. It’s the medium through which consciousness operates. The body and mind are not separate systems. They are one system operating at different scales.
Why this matters practically
Most contemporary wellness culture has gotten this backwards. The assumption is: heal your mind, and your body will follow. Your beliefs create your reality. Your thoughts determine your health.
I think it’s the opposite. Your mitochondria determine your thoughts.
If the fire in your cells is what determines your mental clarity, your emotional resilience, your capacity to think and perceive and integrate — then the path to freedom is metabolic. You cannot reason your way out of a broken engine.
This means the basics matter more than Instagram admits. How you breathe. How often you deliberately push your body into cold. How often you expose yourself to heat. What you eat and when. Whether you do physical practice that actually demands something from you. Whether you spend time without food.
The sophisticated practices — the meditation, the philosophy, the psychological work — these all sit on top of a foundation. That foundation is a functioning mitochondrial system. The Vedic system called this purification: the practices that heat and strengthen the cellular fire so that the higher practices become possible.
In the students I work with, I see this principle repeatedly. The ones who address their tapas first progress faster. Not because they’re trying harder. Because they’ve built the engine.
The ancient texts say it clearly: first purification, then awakening. First tapas, then samadhi. This makes strict biological sense. You’re building a nervous system and a mitochondrial system capable of handling the intensity of awakening. You cannot reach enlightenment on a broken engine.
But here’s what I don’t know yet. I don’t know if the Vedic texts are describing something more than biology. I don’t know if the “fire” they describe is only mitochondrial heat, or if consciousness itself has a thermal dimension we haven’t yet measured. I don’t know if the deepest practices in the Vedic system depend on mitochondrial adaptation, or if mitochondrial adaptation is just the entry point to something else entirely.
What I know is this: the map was drawn long before we had the instruments to verify it. And now that we’re building the instruments, the map keeps being right.
Frequently asked questions
What is tapas in yoga and how does it relate to mitochondria?
Tapas means heat. The Vedic tradition describes it as the internal fire generated through disciplined practice — specific breathing techniques, held postures, fasting, heat and cold exposure. The texts treat it as physiological, not symbolic. When tapas is strong, energy is stable, mind is clear, the capacity for sustained attention increases. When tapas diminishes, everything fails. Modern cellular biology now describes this same process through the lens of mitochondrial hormesis: controlled stress stimulates mitochondria to multiply and function more efficiently. Both systems are describing the same phenomenon — deliberate challenge strengthens the cellular power plants. The difference is language and timespan.
How does mitochondrial hormesis work and what activates it?
Mitochondrial hormesis is the adaptive stress response: controlled challenges signal the cell to build more mitochondrial capacity. The stimulus must be real — there must be genuine stress — but it must also be survivable. Your cells read the signal and respond by multiplying mitochondria and strengthening the ones you have. Heat stress triggers heat shock proteins that repair mitochondrial proteins. Cold stress activates brown fat and stimulates mitochondrial biogenesis. Restricted breathing forces hypoxic adaptation. Sustained physical effort creates ATP demand that forces proliferation. Fasting forces metabolic switching from glucose to fat oxidation, which strengthens the system. The Vedic tapas practices activate all of these. Every classical yoga sequence is a protocol for triggering mitochondrial hormesis.
Can ancient Vedic practices actually strengthen mitochondria?
Yes. Pranayama increases carbon dioxide tolerance and hypoxic stress. Held postures create sustained ATP demand. Fasting forces metabolic switching. Heat exposure triggers heat shock responses. Cold exposure activates brown fat. Sustained physical practice cycles the nervous system through sympathetic and parasympathetic states in exactly the pattern that optimizes mitochondrial function. These weren’t designed by accident. The traditions refined them through five thousand years of direct observation. Modern research is now validating what they encoded.
Miska Käppi is the founder of Ancient Science and creator of The Path. He spent 20+ years studying wisdom traditions across four continents. Learn more about his work →