Summary
Dr. Andrew Fix interviews Kyle Sela, a physical therapist, strength coach, and founder of AVA Cooling Technology, about the science and practical application of palmar cooling for exercise performance. Kyle shares how he first heard about palmar cooling on the Joe Rogan podcast featuring Andrew Huberman, which led him down a rabbit hole into Craig Heller's research at Stanford on glabrous skin and arteriovenous anastomoses (AVAs). Kyle explains the two primary ways heat causes exercise fatigue: at the muscle cell level where rising temperature changes enzyme configurations and reduces contractile efficiency, and at the brain level where the hypothalamus decreases motivation to continue training as a built-in protective mechanism. He describes how Heller's early research with 49ers players showed a 60% improvement in bodyweight dips when athletes used palmar cooling during 3-minute rest breaks. Inspired by these results, Kyle built his own prototype using aluminum with high specific heat capacity and conductivity, consulting Facebook engineering groups for material science advice. His self-experiments showed an 18% improvement in seated shoulder press reps (7 sets to failure) with 3-minute rest breaks, and a 28% improvement in cable rows with just 60-second rest breaks. He discusses how the shorter rest intervals showed even larger benefits, making the technology particularly exciting for sports like basketball with frequent built-in breaks.
Key Points
- Heat causes fatigue through two pathways: enzyme configuration changes at the muscle cell level and motivational shutdown via the hypothalamus
- Glabrous skin (palms, soles, hairless face) contains AVAs — direct artery-to-vein circuits without capillaries — specialized for temperature regulation
- Stanford research with NFL players showed 60% more dips when using palmar cooling during 3-minute rest breaks
- Kyle's self-experiments showed 18% more reps in shoulder press with 3-minute rests, and 28% more in cable rows with 60-second rests
- The device uses aluminum with high specific heat capacity and conductivity to absorb heat without quickly changing temperature
- Shorter rest periods showed larger cooling benefits because the body has less time to naturally dissipate heat
- The cooling effect works both physically (muscle efficiency) and mentally (removing the brain's shutdown signal)
- Training clients naturally gravitated toward the device, picking it up between sets without being prompted
Key Moments
Why we fatigue — heat at the muscle and brain level
Kyle Sela explains the two primary mechanisms of heat-induced fatigue: rising muscle temperature changes enzyme configurations reducing contractile ability, and the hypothalamus decreases motivation to continue training as a protective mechanism.
"Kind of the why behind this, like, so why do, why do we fatigue? Right. So I think that's always a good question to start with. You know, there's, there's nutrition aspects, there's recovery aspects, as far as like sleep and all that stuff goes. But I think something that I underestimated or maybe I never really considered well enough was as we exercise, there's byproducts of exercise. And one of those byproducts of exercise is that our body temperature will rise and we"
The 60% dip improvement at Stanford
Kyle describes Heller's classic dip study with 49ers players where palmar cooling during 3-minute rest breaks produced a 60% improvement in total reps, because athletes got both more reps per set and didn't receive the neurological signal to stop training.
"And let's say that that athlete got 100 reps over seven sets. Five days later, they bring the athlete back in, repeat the same study. And during that three minute rest interval, they have them using their device is that they have the athlete Palmer cool during that three minute rest break. Yeah. And"
Kyle's self-experiment — 18% improvement day after day
Kyle describes his first controlled test with his prototype — 7 sets of seated shoulder press to failure. Day one without cooling: ~128 reps. Day two with cooling (despite being sore): ~150 reps, an 18% improvement.
"I use my device for the Palmer cooling during the three minutes and I got like 150 something reps. So it was actually, I think it calculated out to like an 18% bump in performance, which, you know, as a strength coach or physical or anybody like that's a pretty awesome improvement on that very next day."
28% improvement with shorter rest periods
Kyle's second test using cable rows with added jumping lunges and only 60-second rest breaks showed an even larger 28% improvement — suggesting palmar cooling has a bigger effect when natural recovery time is shorter.
"I threw in like a jumping lunge exercise to jack my heart rate up just to get some temperature going. And then I only did a 60 second rest break. And the comparison was a 30%, like a 28% bump in reps to failure."
