Dr. Craig Heller on Huberman Lab: How Palm Cooling Works

During anaerobic exercise, active muscles can increase metabolism—and thus heat production—by 50–60x, while blood flow to those muscles cannot increase nearly as much. Once muscle temperature exceeds ~39–39.5°C, a key temperature-sensitive enzyme that allows fuel to enter mitochondria shuts off, effectively cutting off ATP supply and causing sudden muscular failure. This means that heat, not just metabolic waste or neural fatigue, is a major immediate cause of “I can’t do one more rep.”

Cold towels or ice vests on the torso, neck, or head can trick the brain’s thermostat (in the preoptic anterior hypothalamus) into thinking the body is cooler than it is. This can reflexively cause vasoconstriction in the very vessels needed for heat loss, slowing cooling and allowing core temperature to keep rising, even as you feel better. You can subjectively feel refreshed yet remain or become dangerously hyperthermic.

These areas are underlain by specialized arterio-venous shunts that let blood flow directly from arteries to veins, bypassing high-resistance capillaries. Because arteries and veins are low-resistance, they can carry large volumes of blood quickly to the skin surface, making these regions high-throughput heat exchangers. Cooling these areas efficiently cools blood returning to the heart and, in the case of the face and scalp, can directly help cool the brain via venous pathways through the skull.

Plunging hands into ice water or gripping an ice-cold object causes reflex vasoconstriction in the glabrous vessels, closing the very shunts you want open for heat loss. The hand may feel cold afterward because blood flow has been reduced, effectively ‘sealing in’ heat rather than venting it. The optimal strategy is moderate cooling (feels cool, not painfully cold) combined with convective flow (moving fluid or surface) to avoid boundary layers and maintain heat transfer.

In controlled experiments, cooling the palms between sets (about three minutes per rest interval) allowed athletes to maintain performance and add sets rather than dropping off. A notable case: NFL tight end Greg Clark, already in peak condition, went from about five sets totaling ~100–120 dips to performing roughly 300 dips after several weeks of cooling between sets—tripling total work. Crucially, these gains persist; once adaptations occur (more contractile elements, hypertrophy), performance stays elevated even without cooling.