Summary
Andrew Huberman explains how temperature regulation is the most powerful variable for improving physical performance and recovery. He details the three compartments of body temperature regulation — core, periphery, and glabrous skin surfaces (palms, soles of feet, and face) — and how arteriovenous anastomoses (AVAs) in these regions allow rapid heat transfer. Research from Craig Heller's lab at Stanford showed that palmar cooling between sets nearly doubled pull-up output (from 100 to 180 in a session) and significantly extended endurance performance.
The episode covers the mechanism behind exercise fatigue: muscle heating disrupts pyruvate kinase and ATP function, while cardiac drift from elevated body temperature triggers quitting. Huberman provides practical protocols for cooling during workouts using cool (not ice-cold) water on palms, feet, or face, and explains why full-body ice bath immersion after training can block mTOR-mediated muscle growth adaptations. Instead, he recommends targeted glabrous skin cooling for recovery to restore baseline temperature without interfering with hypertrophy signaling.
Key Points
- Palmar cooling between sets nearly doubled pull-up capacity in Stanford research (100 to 180 pull-ups per session)
- Three glabrous skin portals — palms, soles of feet, face — are the most effective sites for dumping or absorbing heat due to arteriovenous anastomoses (AVAs)
- Muscle overheating disrupts pyruvate kinase, shutting down ATP-driven muscle contraction
- Cardiac drift: heat increases heart rate independent of effort, causing earlier quitting during exercise
- Cool water (not ice-cold) is optimal — too-cold water causes vasoconstriction and blocks heat transfer through the palms
- Full-body ice bath after strength training can block mTOR and hypertrophy adaptations — use targeted palmar/plantar cooling instead
- NSAIDs lower body temperature pharmacologically but carry liver and kidney risks during exercise
Key Moments
Palmar cooling for performance: cool the palms between sets to extend exercise capacity
Glabrous skin on palms, soles, and face has special blood vessels for rapid heat exchange. Cooling palms between sets prevents core overheating, the real limiter of performance, extending work capacity dramatically.
"What's special about those areas of your body and the glabrous skin is that the arrangement of vasculature of blood vessels, capillaries, and arteries that serve those regions is very different."
Why cooling the core before exercise backfires -- cool the palms instead
Ice baths before training cool the core and clamp down the vascular system, reducing performance. Instead, cool the palms to extract heat without shutting down blood flow to muscles.
"Here's what you don't want to do. You don't want to cool the core if you want to cool the body, right? If it's a very hot day and you're going to train, getting into an ice bath first, sure, it will cool you down, but that's not going to be as effective as cooling the palms, the bottoms of the feet, and the face. The one that I've tried, because in anticipation of this episode, was the dips where then I would cool my hands. I actually decided to cool the bottoms of my feet as well because it just feels good and it's particularly hot out lately. So no shoes or socks on, put my feet into the bottoms of my feet, just kind of hovering about a centimeter or two below the surface of a bucket of water that was just slightly, it felt cool, slightly cooler than body temperature or so. It just basically what came out of the spigot after I let it run for a little bit. And indeed, I saw a 60% increase in the number of dips that I can do in a single session. So it's actually a quite significant effect and you don't have to be perfectly precise in order to do it. I'd like to take a quick break and acknowledge one of our sponsors, Function. Last year, I became a Function member after searching for the most comprehensive approach to lab testing. Function provides over 100 advanced lab tests that give you a key snapshot of your entire bodily health. This snapshot offers you with insights on your heart health, hormone health, immune functioning, nutrient levels, and much more. They've also recently added tests for toxins, such as BPA exposure from harmful plastics, and tests for PFASs, or forever chemicals. Function not only provides testing of over 100 biomarkers key to your physical and mental health, but it also analyzes these results and provides insights from top doctors who are expert in the relevant areas. For example, in one of my first tests with Function, I learned that I had elevated levels of mercury in my blood. Function not only helped me detect that, but offered insights into how best to reduce my mercury levels, which included limiting my tuna consumption. I'd been eating a lot of tuna, while also making an effort to eat more leafy greens and supplementing with NAC and acetylcysteine, both of which can support glutathione production and detoxification."
