Huberman LabUsing Temperature for Performance, Brain & Body Health | Dr. Craig Heller
CHAPTERS
- 0:00 – 21:20
Introduction, Guest Background, and Sponsor Messages
Andrew Huberman introduces the episode’s focus on thermoregulation and performance, presenting guest Dr. Craig Heller, a Stanford biologist and neuroscientist. He briefly reviews Heller’s research areas and outlines the central claim that temperature control is one of the most powerful levers for mental and physical performance. Huberman then delivers sponsor reads before the main conversation begins.
- •Dr. Craig Heller studies thermoregulation, Down syndrome, and circadian rhythms at Stanford.
- •Core body temperature strongly affects neuronal and organ function, and thus performance.
- •Huberman frames temperature control as possibly the most powerful performance tool.
- •Sponsors: ROKA (eyewear), InsideTracker (blood/DNA analytics), Athletic Greens (AG1).
- 21:20 – 29:30
Cold Exposure Basics: Ice Baths, Showers, and Vasoconstriction
Heller explains the acute physiological response to first-time cold exposure, highlighting the adrenaline surge and vasoconstriction. He distinguishes between whole-body cold immersion and cold showers and introduces the concept of boundary layers of water near the skin. He emphasizes that while cold feels stimulating, it does not automatically translate into improved physiology or performance.
- •Cold shock produces a strong adrenaline spike, explaining why people feel ‘different’ after cryo chambers or ice baths.
- •Cold showers and baths trigger vasoconstriction, which can actually reduce heat loss from most of the skin.
- •In a still bath, a boundary layer of water near the skin equilibrates with body temperature, acting as insulation.
- •Moving in cold water or being under a shower breaks the boundary layer, increasing heat loss.
- 29:30 – 37:00
Pre-Cooling for Aerobic Performance and Warm-Up Strategies
The discussion turns to pre-cooling as a strategy to extend aerobic performance by increasing the body’s heat storage capacity. Heller explains how a brief cool shower or targeted cooling after warm-up can delay the onset of overheating during long runs or hot competitions. He notes that athletes can use this extra thermal ‘headroom’ either to go farther at the same pace or to go faster over the same distance.
- •For aerobic work, body heat production rises gradually and eventually impairs performance.
- •Pre-cooling after warm-up (dropping core ~0.5°C) increases the thermal buffer before hitting performance-limiting temperatures.
- •Only a few minutes of cooling are needed before core thermoregulatory mechanisms shut off additional heat loss.
- •Athletes can use the cooling-induced buffer to extend distance (pacers) or increase pace (forcers).
- 37:00 – 47:00
Muscle Overheating, Enzyme Shutdown, and the Real Cause of ‘Failure’
Heller explains that in anaerobic exercise, specific working muscles can become locally hyperthermic even when core temperature remains moderate. He describes how muscle metabolism can increase 50–60 fold while blood flow cannot match it, leading to rapid heat buildup. Key metabolic enzymes, including those feeding fuel into mitochondria, are temperature-sensitive; when muscle temperature exceeds ~39–39.5°C, these enzymes shut down, causing sudden muscle failure.
- •Humans are only ~20% efficient; ~80% of energy from food is lost as heat, much of it in working muscle.
- •Local muscle metabolism can increase 50–60x during intense anaerobic work, far exceeding the increase in blood flow.
- •Heat can’t leave contracting muscle quickly because contraction compresses blood vessels; blood is the only significant heat carrier.
- •Critical enzymes like temperature-sensitive pyruvate kinase limit output when the muscle gets too hot, producing ‘one more rep’ failure.
- •Glycogen depletion is slower than perceived failure; short rests restore performance because temperature and metabolites change, not glycogen replenishment.
- 47:00 – 1:00:00
Why Cooling Thighs, Neck, or Torso Often Backfires
Huberman and Heller dissect why popular cooling methods—ice towels on the neck, cold packs on large muscles, drinking ice water—are relatively inefficient or even harmful for performance. Heller introduces the brain’s thermostat in the preoptic/anterior hypothalamus and explains how cooling some skin areas can send misleading signals. Cooling the thermostat region can reduce perceived heat and shut down global heat-loss responses while core temperature continues to climb.
- •The preoptic anterior hypothalamus acts as a central thermostat, integrating thermal inputs from across the body.
- •Cooling the torso or neck can make you *feel* cooler by changing thermostat inputs, but may slow actual heat loss (vasoconstriction of portals).
- •Putting a cold towel on the neck cools blood heading to the brain, protecting it somewhat but also lowering perceived temperature dangerously.
- •Cold packs on big muscles like quads are blocked by layers of insulating tissue; they remove little heat compared to portal cooling.
- •Ice water ingestion helps but has limited capacity and risks overhydration; it cannot carry away heat fast enough by itself.
- 1:00:00 – 1:10:30
Discovery of Glabrous Skin Portals and AVAs
Heller introduces glabrous (hairless) skin regions—palms, soles, and upper face—as specialized heat-loss portals in mammals. He explains arterio-venous anastomoses (AVAs), shunts that connect arteries directly to veins, bypassing capillaries and enabling very high blood flow for heat exchange. These structures evolved in mammals under fur, where only hairless pads and faces could dissipate heat effectively.
- •Glabrous skin (no hair follicles) in humans is limited to palms, soles, and upper face; in other mammals, also paw pads, ears, tongue, etc.
- •AVAs in these regions connect arteries to veins directly, allowing low-resistance, high-volume blood flow for heat exchange.
- •Palms appear red and warm when vasodilated; squeezing them or cold exposure can blanch them (vasoconstriction).
- •Gripping handlebars tightly or wearing thick gloves impairs heat loss through palmar AVAs and can reduce cycling or running performance.
- •Animals instinctively use their portals—e.g., dogs standing in water—to dump heat.
- 1:10:30 – 1:25:00
Performance Experiments: Dips, Push-Ups, and Golf with Palmar Cooling
Heller recounts several key experiments where palmar cooling produced stunning gains in work capacity. An NFL tight end doubled his dip volume in one day and tripled it over a month, while naive students reached >800 push-ups in a single session. Golfers and elite military operators reported significantly improved performance and endurance in hot conditions by using the cooling devices between efforts.
- •In a controlled protocol (5 sets of dips with 3-minute intervals), palmar cooling allowed an NFL player to double total dips day-over-day and later triple his baseline across weeks.
- •Naive female students doing 10 sets of push-ups to failure with cooling achieved >800 total reps, with notable upper-body hypertrophy.
- •Delayed onset muscle soreness (DOMS) was dramatically reduced or absent in cooled conditions despite far greater volume.
- •A special operations soldier reported adding ~20 yards to every golf club when using the cooling device on the course.
- •MS patients, who are extremely heat-sensitive, were able to return to summer golfing by using palmar cooling mounted on carts.
- 1:25:00 – 1:34:20
CoolMitt Technology and Practical, Low-Tech Cooling Attempts
Heller describes the CoolMitt device: a palm-cooling system that circulates cool water at an optimal temperature to avoid vasoconstriction. He explains that too-cold stimuli like ice water shut down AVAs, making them ineffective. While the commercial device is in beta with pro teams, military, and federations, he outlines how people might experiment with crude methods like rotating cold packs or frozen items between hands, while warning about limitations.
- •CoolMitt (by Arteria) cools palmar surfaces with a controlled, comfortable temperature and circulating water to maximize heat transfer.
- •Ice-cold water or static frozen packs are counterproductive because they cause vasoconstriction in AVAs.
- •Optimal cooling appears to be in the first 2–3 minutes per interval, based on the exponential decay of heat loss rate.
- •Interim ‘poor man’s’ methods (frozen peas, frozen juice cans) might partially work if rotated between hands and monitored by touch to avoid cold palms.
- •Moving water (convection) is more effective than static cold objects due to boundary layer effects.
- 1:34:20 – 1:48:40
Hyperthermia, Hypothermia, and Updating Medical Protocols
The conversation moves to clinical applications of temperature control. Heller describes how standard hyperthermia treatment (cold packs in groin, axillae, neck) performs poorly compared to portal cooling. He also recounts how his lab developed a negative-pressure limb-heating device that dramatically accelerated rewarming and stopped shivering in post-anesthesia patients, showing the clinical potential of targeting glabrous skin.
- •Standard hyperthermia protocols place cold packs on the neck, groin, and armpits to cool blood vessels, but this is less efficient than cooling radiating surfaces (palms/soles/face).
- •Heller’s lab showed that moving identical cold packs to glabrous skin doubled the core cooling rate.
- •In recovery rooms, hypothermic patients under blankets and heat lamps took hours to stop shivering.
- •A suction-assisted limb-warming device targeting glabrous skin rewarmed patients and stopped shivering in ~8–9 minutes.
- •These findings have not yet become standard practice in hospitals, highlighting a lag between physiology research and medical protocols.
- 1:48:40 – 1:54:40
Brown Fat, Shivering, NEAT, and Misunderstood ‘Thermogenics’
Heller discusses brown adipose tissue, shivering, NEAT (non-exercise activity thermogenesis), and popular misconceptions about targeting brown fat. He notes that human brown fat is distributed and not concentrated between the shoulder blades as often claimed online. The idea of ice packs on the upper back ‘activating brown fat’ is mostly misdirected; any significant core cooling will activate sympathetic pathways, including brown fat. He also clarifies that any muscular activity—even fidgeting—produces disproportionate heat relative to movement work.
- •True hibernators like ground squirrels use localized brown fat as ‘kindling’ to rewarm before violent shivering resumes.
- •Humans have brown fat but it’s dispersed, not neatly localized between scapulae as textbooks or blogs often depict.
- •Ice on the upper back likely cools vertebral arteries and the hypothalamus more than any special brown fat depot.
- •NEAT (fidgeting, foot-tapping) can substantially raise daily energy expenditure because muscle is only ~20% efficient—80% of energy goes to heat.
- •Thermogenic energy drinks often combine caffeine, vasodilators, and sugars; their net effect on performance is unclear and may be undermined by caffeine’s antagonism of adenosine, which normally promotes local vasodilation in working muscle.
- 1:54:40 – 2:04:00
Comparing Cooling to Steroids and Final Reflections
In a provocative comparison, Heller notes that anabolic steroids in reputable bench-press studies yield roughly 1% performance improvement per week, while palmar cooling interventions can produce ~300% gains in a month for certain protocols. He emphasizes that cooling-induced adaptations (strength gains, hypertrophy) persist even when cooling is withdrawn, indicating true conditioning rather than a transient trick. The episode closes with discussion of sleep socks, thermal comfort, and Huberman’s closing remarks and resources.
- •Meta-analysis of steroid studies shows modest ~1% weekly gains in bench press capacity versus much larger gains from cooling-assisted training volume.
- •Cooling supports greater work volume with less muscle damage, enabling faster and larger physiological adaptations.
- •Gains from cooling-assisted training persist after stopping cooling, indicating real strength and hypertrophy adaptations.
- •Socks in bed may improve subjective comfort by insulating particularly temperature-sensitive toes, though they also reduce foot portal heat loss.
- •Huberman closes with instructions on supporting the podcast, following on social media, using Thorne supplements, and donating to research.
- 2:04:00
Sleep, Circadian Rhythms, and Why Cool Rooms Actually Help
Heller briefly addresses sleep hygiene and the role of temperature in sleep. He endorses behavioral strategies like consistent schedules, avoiding screens before bed, and relaxing pre-sleep routines. Crucially, he clarifies that cool sleeping environments are beneficial because they allow passive thermoregulation by exposing or covering glabrous regions—especially hands, feet, and face—consistent with the circadian drop in the body’s temperature set-point.
- •Modern sleep medicine favors cognitive behavioral therapy and sleep hygiene over pharmacology for chronic insomnia.
- •Blue-light screens before bed delay circadian signals for sleep in the hypothalamus.
- •A warm bath can promote sleep partly via subsequent cooling, aligning with the circadian drop in temperature set-point.
- •At night, the thermostat set-point in the hypothalamus decreases; people often sleep hot then wake and throw off covers.
- •In a cool room, you can regulate temperature passively by sticking hands, feet, or face out, using portal surfaces as adjustable radiators.
