Lactate and the burn from exercise is not what you think. Dr Jared Rutter top scientist on the topics of metabolism and mitochondria on the Huberman Lab podcast out now.

Full episode

Jared is such a good guy and incredible scientist. I'm delighted to see him on the podcast.

Hydrogen ions piling up cause the burn, and lactate is what muscle makes while soaking them up. Heart and brain then pull that lactate from the blood and burn it as fuel, which is why you can still think mid-sprint. The molecule blamed for fatigue is the cleanup crew.

Thanks Andrew, I will listen to it. My daughter loves your podcasts. she’s 8, and we listened to the episode with Joe Liemandt together. We got some beautiful insights from it. We’re from Argentina, living in the US. Thanks for spreading good things.

lactate finally getting its apology after decades of lactic acid slander

It's fascinating how our perceptions of exercise physiology can change.Interesting!

Lactate & brain as well

Crazy how thirty years of gym folklore branded lactate as toxic waste. Turns out the myocardium and brain actively prefer lactate over glucose when demand spikes. The burn isn't cellular damage. It is high-octane metabolic currency being shuttled directly to the engine room. Brilliant closed-loop recycling system that fitness culture completely misinterpreted for decades.

copenhagen put numbers on this. once blood lactate climbed, the brain covered about a quarter of its energy with it and pulled in less sugar.

The lactate-as-fuel vs. “waste product” distinction still gets muddled—does the episode address how much the answer depends on exercise intensity and tissue? I’ve been digging into this with Sci-Quest:

Lactate burn isn’t the enemy — it’s a signal. Most people quit the session the second it shows up. Sit one more minute in zone 2 after it hits and the adaptation actually sticks.

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Lactate burn isn’t failure. It’s feedback. If you bail the second it shows up, you never teach the system to clear it. Stay one more easy minute.

The lactate to BDNF signal is real work, with one caveat: the direct evidence is rodent hippocampus, not human trials. Very low certainty in our grading. We checked all 50 claims in the episode, each with its sources:

I wish less people felt like scientists after mentioning the mythical “lactic acid”. The burn is from a buildup of protons, lactate actually helps buffer the burn you feel. That’s exactly why sodium bicarbonate can be used in training, it acts as a buffer as your cells become more acidic. Would be interesting to see what Dr. Jared has to say.

The “lactate is just waste” idea refuses to die. This clip should help.

thought that was edward norton for half a second

Lactate binds histones directly. The mark is called H3K18la, and it switches on inflammation-resolving genes like Arg1 hours after the effort ends. 28 of these sites exist on core histones alone. Does Dr. Rutter's mitochondrial work connect to this, exercise lactylation driving part of training's anti-inflammatory effect?

Excellent discussion. Lactate is far more than a waste product. It serves as an important fuel and signaling molecule during exercise. Dr. Jared Rutter’s work connecting metabolism, mitochondria, and human health makes this a must-listen episode.

That podcast interview highlights a vital physiological fact that mainstream fitness culture completely misinterprets. In my clinical biochemistry and human performance work, it is well-established that lactate is not a waste product responsible for muscle fatigue or the acute burning sensation during intense exercise. Lactate is actually a highly efficient, preferred fuel source that mitochondria eagerly pull from the circulation to rapidly generate cellular energy when oxygen demands spike. The actual burning sensation is triggered by an accumulation of excess hydrogen ions that lower muscular pH, creating an acidic environment that temporarily disrupts cell signaling. Shifting the public narrative from viewing lactate as a toxic byproduct to recognizing it as a critical metabolic resource is a major step toward optimizing elite athletic training.

Lactate is an active metabolic signaling molecule and preferred cellular fuel for the brain and heart during stress, not just metabolic waste. When you shift the perspective from managing exhaustion to optimizing mitochondrial energy transport, metabolic flexibility becomes the real target.