Huberman LabDr. Craig Heller on Huberman Lab: How Palm Cooling Works
Glabrous skin on the palms, soles, and upper face dissipates heat through AVAs; cooling these spots between sets extends reps and delays muscular fatigue.
CHAPTERS
- 0:00 – 3:30
Cold Showers, Ice Baths, and the Real ‘Benefit’ of Cold
Huberman introduces Dr. Craig Heller and raises the popular interest in cold showers and ice baths. Heller explains that while these induce a strong adrenaline-driven shock, the perceived benefits often do not translate into meaningful improvements in physiology or performance and can sometimes hinder heat loss via vasoconstriction.
- •Cold showers and ice baths trigger a strong shock response and adrenaline surge.
- •General cold exposure can drive vasoconstriction, making it harder for the body to shed heat.
- •In full cold immersion, large surface area can still drive net heat loss despite vasoconstriction.
- •Primary evolutionary portals of heat loss are specific regions, not the whole body surface.
- 3:30 – 6:50
Heat Portals: Palms, Soles, and Upper Face Explained
Heller introduces ‘glabrous’ skin—hairless regions such as palms, soles, and upper face—as special heat-exchange portals. He describes the underlying arterio-venous shunts that allow high-volume blood flow for rapid heat transfer and contrasts these with normal capillary-based skin.
- •Glabrous skin means hairless skin without hair follicles; key areas are palms, soles, and upper face.
- •These areas contain arterio-venous shunts that bypass capillaries, allowing high blood flow.
- •Heat status can often be inferred by shaking someone’s hand (hot vs cold).
- •Most of the rest of human skin is still ‘hairy’ in structure and not optimized for rapid heat loss.
- 6:50 – 9:50
Aerobic vs Anaerobic Exercise: How Heat Limits Performance
The discussion shifts to how heat buildup limits both endurance and strength. For aerobic efforts, pre-cooling increases the body’s capacity to absorb heat, improving time to fatigue. For anaerobic work, localized muscle heating rapidly impairs enzyme function and ATP production, triggering sudden muscular failure.
- •In prolonged aerobic activity, core temperature gradually rises and eventually impairs performance.
- •A cool shower before a long run can delay sweating onset and heat stress, improving performance.
- •During anaerobic efforts, only specific active muscles heat up dramatically (local effect).
- •A temperature-sensitive enzyme shuts off above ~39–39.5°C, cutting fuel supply to mitochondria.
- 9:50 – 16:00
Why Local Cooling (Thighs, Neck, Ice Water) Often Fails
Huberman explores why simply cooling hot muscles, drinking ice water, or using neck/head ice packs doesn’t reliably fix performance-limiting heat. Heller explains that muscles are insulated, heat leaves primarily via blood, and cooling certain areas can mislead the brain’s thermostat, cause vasoconstriction, and actually slow true core cooling.
- •Muscles are insulated by skin and fascia; surface cooling doesn’t rapidly cool deep muscle tissue.
- •Heat exits muscles via blood flow, which is limited during contraction.
- •Drinking ice water absorbs some heat but is limited by volume and potential blood dilution.
- •Cooling the neck/head strongly signals the brain and can make you feel cool while core temperature remains high.
- •Cooling the torso can cause vasoconstriction in heat loss portals, reducing real heat dissipation.
- 16:00 – 20:30
Hyperthermia Risks and Misleading Sensations of Coolness
They examine the dangers of hyperthermia and why it’s tricky to self-diagnose. Heller notes that as individuals approach heat stroke, they may stop sweating and vasoconstrict, feel terrible yet keep pushing due to motivation, and that subjectively feeling better from local cooling doesn’t guarantee safe core temperatures.
- •The brain’s thermostat is in the preoptic anterior hypothalamus and relies on widespread temperature inputs.
- •Cooling the thermostat (e.g., neck, head) without cooling the core can mask danger.
- •Hyperthermia symptoms include exhaustion, feeling miserable, very high heart rate, and sometimes reduced sweating.
- •Motivated athletes can override discomfort and push into dangerous heatstroke territory.
- •Historical athletic deaths from heatstroke often occur in practice, not competition.
- 20:30 – 33:00
Glabrous Portals in Mammals and Practical Implications (Hands, Feet, Face)
Heller connects human heat portals to mammalian evolution, explaining that fur-covered animals evolved specialized non-furred regions (pads, ears, faces) for heat loss. They translate this into practical advice: don’t over-grip handlebars, avoid thick gloves and socks when possible, and understand why pouring water on the head can selectively cool the brain.
- •Other mammals use hairless pads, ears, and faces with similar vasculature for heat exchange.
- •Arterio-venous shunts in glabrous skin allow low-resistance, high-flow heat dumping.
- •Gripping handlebars tightly can compress and reduce blood flow through hand portals.
- •Thin gloves and socks allow better heat loss than thick ones when cooling is desired.
- •Facial/scalp cooling can reverse venous flow patterns and help cool the brain.
- •Brain cooling may reduce swelling after injury, but its benefits for concussion are still controversial.
- 33:00 – 37:00
Palmar Cooling Breakthrough: The Greg Clark Dips Experiment
They recount a pivotal case study with NFL tight end Greg Clark that demonstrated how palmar cooling can massively boost work volume in strength training. By cooling his palms between sets of dips using a specialized device, Clark first doubled and then eventually tripled his total dip count over several weeks.
- •Clark’s baseline: ~40 dips in set one, rapidly declining over five sets.
- •Using palmar cooling between sets (3-minute standard intervals), all sets improved over control.
- •He felt he could keep adding sets and reps, indicating heat was previously the limiting factor.
- •Within about a month of twice-weekly sessions, total dips rose to ~300 (about 3x baseline).
- •Published research shows similar effects for bench press, push-ups, and other strength tasks.
- 37:00 – 40:00
Endurance in Extreme Heat and Why Palms/Soles/Face Beat Armpits/Groin
The conversation moves to endurance studies with treadmill walking in hot environments. Continuous cooling of palms, soles, and face dramatically outperforms standard medical field protocols (cold packs in armpits, groin, neck) for lowering core temperature and extending endurance.
- •In a ~40°C lab environment, portal cooling roughly doubled time to exhaustion during treadmill walking.
- •Devices suspended from the ceiling allowed subjects to cool hands continuously while walking.
- •A controlled study showed palms/soles/face cooling provided about double the cooling rate of packs in armpits, groin, and neck.
- •Standard medical recommendations may be suboptimal compared to targeting glabrous portals.
- 40:00 – 43:00
Coolmitt Technology: Optimal Temperature, Timing, and Why Ice Water Fails
They discuss the specific device developed from Heller’s work (Coolmitt by Arteria) and why its design choices matter. The mitt provides cool—not ice-cold—convective cooling to the palms, exploiting the steep part of the heat-loss curve in short intervals while avoiding vasoconstriction.
- •Company: Arteria; product and site: Coolmitt (coolmitt.com).
- •Technology is being beta-tested by NFL, college teams, Olympic athletes, Navy SEALs, MLB, NBA, and NTA.
- •The mitt cools a surface the hand grips at an optimally cool temperature, not freezing.
- •Ice water immersion of hands is counterproductive because it causes vasoconstriction of heat portals.
- •Heat loss is an exponentially declining curve; about three minutes captures the most efficient portion.
- •Longer cooling provides more benefit but with diminishing returns.
- 43:00 – 45:00
DIY Palmar Cooling and Ensuring You Don’t Close the Portals
Huberman asks for practical at-home strategies while Coolmitt expands availability. Heller offers a simple test—whether your hands feel warm or cold after holding a frozen pack—to see if you’ve preserved or shut down blood flow, and explains limitations of static packs under feet or on the face compared with moving cooling mediums.
- •DIY approach: use frozen peas/blueberries or similar as a crude hand cooler between sets.
- •Key test: after cooling, if your palm feels cold to someone else, you’ve induced vasoconstriction; if it feels warm, blood still flows and cooling is effective.
- •Static packs under feet or on the face develop a boundary layer that reduces heat transfer compared to convective systems.
- •Surface area and fluid motion are critical to effective, fast heat exchange.
- •Hands, soles, and upper face cooled properly can double cooling rate vs traditional pack placements.
- 45:00
Lasting Adaptations: Keeping Gains After Cooling and Final Advice
In closing, Heller confirms that adaptations made under enhanced work volume with cooling are durable: increased strength and muscle size remain even when cooling is no longer used. Huberman encourages listeners to apply the principles with whatever tools they have and thanks Heller for translating rigorous lab science into actionable protocols.
- •Training with palmar cooling allows higher work volume, driving greater adaptation.
- •Gains in strength and muscle from higher work volume persist even if you later stop cooling.
- •Cooling is a performance-enhancing tool, not a crutch; it accelerates conditioning.
- •Listeners are encouraged to experiment carefully with glabrous-skin cooling using accessible means.
- •The approach is relevant for mental and physical performance, as overheating impairs both muscles and brain.
