Summary
Andrew Huberman delivers a comprehensive deep dive into the science of palmar cooling and its dramatic effects on exercise performance. He explains the role of arteriovenous anastomoses (AVAs) — specialized blood vessel networks found in the palms, soles of feet, and face — that serve as the body's primary portals for dumping heat and accepting cold. These glabrous skin regions bypass normal capillary beds, allowing rapid core temperature regulation. Huberman walks through research from Craig Heller's lab at Stanford showing that palmar cooling between sets enabled subjects to go from 100 to 600 pull-ups across sessions, and produced bench press gains that outpaced a group taking anabolic steroids. The key mechanism is that rising muscle temperature disrupts pyruvate kinase, a critical enzyme for ATP production, causing both muscular failure and a motivational shutdown via the hypothalamus. By cooling the palms between sets with a device at the right temperature (cool but not ice cold), athletes can keep core temperature in the optimal range and dramatically extend work capacity. The episode also covers practical DIY approaches — using a frozen juice can passed between hands, or cool water in a sink — and warns against common mistakes like cooling the neck (which can trick the hypothalamus into heat-preservation mode) or using ice-cold surfaces that cause vasoconstriction and block the cooling effect.
Key Points
- Palms, soles of feet, and face contain arteriovenous anastomoses (AVAs) that bypass capillaries and serve as the body's most efficient heat exchange portals
- Rising muscle temperature disrupts pyruvate kinase, a rate-limiting enzyme for ATP and muscle contraction, causing both muscular failure and motivational shutdown
- Stanford research showed palmar cooling enabled subjects to go from ~100 to 600 pull-ups over several sessions — a 6x increase in work capacity
- A 49ers player saw a 60% increase in dips in a single session using palmar cooling during 3-minute rest breaks
- The cooling group's bench press gains outpaced a group on testosterone cypionate (anabolic steroids)
- The cooling surface must be cool (not ice cold) to avoid triggering vasoconstriction, which would shut down the AVA heat-exchange pathway
- Cardiac drift — where heat increases heart rate independent of effort — is a major driver of endurance fatigue, and palmar cooling counteracts it
- DIY approach: pass a frozen juice can or cold soda between hands for 10-30 seconds between sets; avoid cooling the neck as it may signal the hypothalamus to preserve heat
Key Moments
Glabrous skin and AVAs — the body's heat exchange portals
Huberman explains the three body surfaces with specialized vasculature for temperature regulation — palms, soles of feet, and face — and introduces arteriovenous anastomoses (AVAs) that bypass capillaries for rapid heat exchange.
"You have three compartments for increasing or dumping heat in your body. One is your core. The other is your periphery. But then there's a third component, which is there are three locations on your body that are far better at passing heat out of the body and bringing cool into the body, such that you can heat up or cool your body everywhere very quickly. Those three areas are your face, the palms of your hands and the bottoms of your feet."
100 to 600 pull-ups with palmar cooling
Huberman describes the staggering Stanford data where subjects went from about 100 pull-ups to 180 on day two with cooling, and eventually to 600 pull-ups over several weeks — and could maintain gains even without cooling.
"They started cooling after every other set. The person would just hold the cold tube, cool down the body after every other set. And they found that they went to 180 pull-ups, which is incredible, it's a near doubling. And by doing this repeatedly over several sessions, over several weeks, they quickly went in the cooling group from a maximum of somewhere between 180 and 200 to 600 pull-ups in the equivalent amount of time, which is absolutely incredible."
Palmar cooling outperformed anabolic steroids
The bench press study included a control group on testosterone cypionate. The steroid group improved at about 1% per week, while the palmar cooling group dramatically outpaced them.
"The bench press study was pretty interesting because they actually had a control group that was admittedly taking specific amounts of anabolic steroids. The anabolic steroid was testosterone cipionate, which is essentially testosterone. And indeed the testosterone cipionate, the steroid group improved at a rate of about 1% per week."
Heat, willpower, and cardiac drift
Huberman explains how body heat directly reduces willpower through a physiological mechanism, and introduces cardiac drift — where rising temperature increases heart rate independent of effort, causing people to quit.
"If you are cool, if your body temperature is in a particular range, not only can you go further, but you will go further if you want to. Said differently, if you heat up too much, you will stop or you will die."
DIY palmar cooling with a frozen juice can
Huberman shares Craig Heller's recommended poor man's approach to palmar cooling — passing a frozen juice can or cold soda between hands — and explains why you must pass it back and forth to avoid vasoconstriction.
"You could take a frozen juice can, if you have one of those, or a very cold can of soda, and you would want to pass it back and forth between your two hands. The reason the passing back and forth is really important is because you don't want it to be so cold that you constrict those venous portals that will allow cold to go into the body."
