--- canonical_name: Palm Cooling alternate_names: Palmar Cooling, Hand Cooling, Glabrous Skin Cooling, Interset Palm Cooling, Rapid Thermal Exchanger, RTX, CoreControl, CoolMitt canonical_topic: Palm Cooling to Improve Exercise Performance short_topic_lc: palm_cooling_exercise creation_date: 2026-0927-1253 creator_ai_fullname: Opus 5.5 ep_keywords: Cooling Therapy, Thermoregulation, Precooling --- # Palm Cooling to Improve Exercise Performance
Evidence Review created on 09/27/2026 using [AI4L](https://github.com/forever-healthy/AI4L) / Opus 5.5 **Also known as:** Palmar Cooling, Hand Cooling, Glabrous Skin Cooling, Interset Palm Cooling, Rapid Thermal Exchanger, RTX, CoreControl, CoolMitt ## Motivation Palm cooling (also called palmar cooling) means resting the palms against a cool surface or holding them in cool water for a few minutes, usually between sets or intervals of exercise. The palms contain special blood vessels that carry large amounts of warm blood close to the skin, so cooling them is proposed as a quick way to pull heat out of the body. The interest comes from the idea that rising body heat is one of the things that ends hard efforts early. For adults who train to stay strong and fit over the long term, a simple way to get more from each session would matter. The method grew out of university research on how the body controls its temperature and later spread through sports podcasts, professional teams and consumer cooling gloves. It drew attention when its inventors began testing it on endurance in the heat and on repeated weight-training sets, and independent laboratories have since tested the same uses. This review examines whether palm cooling improves endurance and strength-training performance, how large and how reliable any effect is, what risks it carries, and how the source of the research shapes the overall picture. **[Benefits](#expected-benefits) - [Risks](#potential-risks--side-effects) - [Protocol](#therapeutic-protocol) - [Conclusion](#conclusion)** ## Recommended Reading This section lists high-level expert and research sources that discuss palm cooling for exercise performance in depth. - [Dr. Craig Heller: Using Temperature for Performance, Brain & Body Health](https://www.hubermanlab.com/episode/dr-craig-heller-using-temperature-for-performance-brain-and-body-health) - Andrew Huberman Stanford biologist Craig Heller, co-inventor of palm-cooling devices, explains palm blood-vessel physiology, why ice-cold surfaces backfire, and his reported training gains; his commercial interest in the CoolMitt device is relevant context. - [Effects of heat removal through the hand on metabolism and performance during cycling exercise in the heat](https://pubmed.ncbi.nlm.nih.gov/15855685/) - Hsu et al., 2005 Cyclists using a palm heat-extraction device in 32 °C heat finished a 30-km time trial about 6% faster, with a smaller ear-temperature rise and lower oxygen use and lactate (a muscle-work by-product). - [Palm cooling delays fatigue during high-intensity bench press exercise](https://pubmed.ncbi.nlm.nih.gov/20139781/) - Kwon et al., 2010 The most-cited independent resistance-training trial: cooling the palms between bench press (lying barbell press) sets raised total lifting volume in trained men and lowered perceived effort. - [Cool in theory, not in practice: Effects of interset palm cooling on resistance exercise performance and psychophysiology responses](https://pubmed.ncbi.nlm.nih.gov/42472446/) - Piñero et al., 2026 A randomized crossover trial (each person tested under every condition) in 25 trained adults found interset (between-set) palm cooling unlikely to change repetitions, volume, effort ratings or lactate (a muscle-work by-product). - [Arterio-venous anastomoses in the human skin and their role in temperature control](https://pubmed.ncbi.nlm.nih.gov/27227081/) - Walløe, 2016 Explains arteriovenous anastomoses (direct shunts between small arteries and veins) in the palms and soles, the heat-releasing vessels that palm cooling targets, and when they open or close. No relevant content on palm cooling was found from Peter Attia, Rhonda Patrick, Chris Kresser or Lifespan.io; their site searches and web searches returned nothing on the topic. The Life Extension site search could not be retrieved, and web searches found no Life Extension Magazine article on palm cooling. ## Grokipedia - [Palm cooling](https://grokipedia.com/page/Palm_cooling) A dedicated overview of palm-cooling physiology, typical 10–16 °C protocols and reported training gains; it leans heavily on Stanford-group findings and gives little weight to the null trials. ## Examine No Examine article on palm cooling exists; the site's search returns only unrelated supplement pages. ## ConsumerLab No ConsumerLab article on palm cooling exists; the site's search returns only unrelated product reviews. ## Systematic Reviews This section lists systematic reviews and meta-analyses that pool palm or hand cooling with other cooling methods, since none is dedicated to palm cooling alone. - [Cooling during exercise enhances performances, but the cooled body areas matter: A systematic review with meta-analyses](https://pubmed.ncbi.nlm.nih.gov/31340407/) - Douzi et al., 2019 Pooling 45 cooling-during-exercise studies, benefits depended on body site; internal, face, neck and torso cooling ranked highest, not the hands. - [Effects of different external cooling placements prior to and during exercise on athletic performance in the heat: A systematic review and meta-analysis](https://pubmed.ncbi.nlm.nih.gov/36703929/) - Jiang et al., 2022 Across 60 studies including palm-cooling devices and gloves, limb and hand cooling gave the smallest performance gain of the three cooling-site groups. - [Practical Cooling Strategies During Continuous Exercise in Hot Environments: A Systematic Review and Meta-Analysis](https://pubmed.ncbi.nlm.nih.gov/27480762/) - Ruddock et al., 2017 Fourteen trials; cooling eased perceived effort and heat perception without lowering core temperature. Only one trial used a palm cold pack. - [Effect of Interset Strategies on Acute Resistance Training Performance and Physiological Responses: A Systematic Review](https://pubmed.ncbi.nlm.nih.gov/30946261/) - Latella et al., 2019 Among 26 studies of between-set strategies, cooling (including palm cooling) was one of the more effective methods for repetitions, amid heterogeneous designs. No systematic review or meta-analysis addresses the principal risks of palm cooling (cold pain and performance loss when cooling is too cold); that side of the trade-off is unrepresented. ## Mechanism of Action As a physical intervention, palm cooling has no half-life or drug metabolism. The palms, soles and upper face are covered by glabrous (hairless) skin rich in arteriovenous anastomoses (AVAs, direct shunts between small arteries and veins). When the body is warm, AVAs open and send large volumes of blood through venous plexuses (networks of small veins) just under the skin, making these areas the body's main radiators ([review by Walløe, 2016](https://pubmed.ncbi.nlm.nih.gov/27227081/)). Palm cooling places this surface against a cool object or water, usually 10–16 °C. Blood cooled in the palm returns to the core, so heat is drawn from the circulating blood. Early Stanford devices added mild subatmospheric pressure (a gentle vacuum around the hand) to hold these vessels open ([Grahn et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15879169/)). A surface that is too cold triggers vasoconstriction (narrowing of blood vessels) and pain, which closes the shunts; protocols therefore avoid ice-cold contact. Competing explanations exist: - **Thermal:** lower core and muscle temperature delays heat-related fatigue; the Stanford group links rising core temperature to earlier lifting fatigue ([Grahn et al., 2012](https://pubmed.ncbi.nlm.nih.gov/22076097/)). - **Perceptual and arousal:** palm heating also raised lifting volume in women ([Kwon et al., 2015](https://pubmed.ncbi.nlm.nih.gov/23722108/)), and a sham immersion (fake treatment in neutral water) reproduced part of the gain ([Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)), pointing to sensory, arousal or placebo effects. - **Skeptical view:** measured heat extraction at rest is only about 42 W, modest next to other cooling methods ([Kuennen et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20033702/)), and several trials saw no core-temperature change during exercise. ## Historical Context & Evolution Palm cooling began as a clinical tool. Stanford biologists H. Craig Heller and Dennis Grahn, studying how mammals shed and conserve heat, built a hand chamber combining mild vacuum with a warm or cool surface. Its original intended use was rewarming people after anesthesia or cold exposure ([Grahn et al., 1998](https://pubmed.ncbi.nlm.nih.gov/9804564/)); an early independent test in surgical patients found no faster rewarming ([Smith et al., 1999](https://pubmed.ncbi.nlm.nih.gov/10589645/)). The same principle was then applied in reverse to relieve heat strain in soldiers and workers wearing insulating protective gear ([Grahn et al., 2009](https://pubmed.ncbi.nlm.nih.gov/19640130/)). Interest in health and performance optimization followed a 2005 report that heat extraction through one palm extended walking time in 40 °C heat ([Grahn et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15879169/)) and later claims of large gains in lifting volume and strength ([Grahn et al., 2012](https://pubmed.ncbi.nlm.nih.gov/22076097/)). The technology was patented and sold as CoreControl and later CoolMitt, and podcasts carried it to athletes and teams. Independent laboratories produced mixed findings. One group reproduced higher bench press volume ([Kwon et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20139781/)) yet saw no slowing of overheating during walking ([Amorim et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20725114/)); a commercial device did not help interval running ([Walker et al., 2009](https://pubmed.ncbi.nlm.nih.gov/19910808/)). Since 2023, better-controlled trials have split: a double-blind trial found no effect ([McMahon & Kennedy, 2023](https://pubmed.ncbi.nlm.nih.gov/37399240/)), while a sham-controlled trial still reported gains, part of them also seen with the sham ([Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)). What changed is trial design rather than a decisive new finding; the question remains open on both sides. ## Expected Benefits ### High 🟩 🟩 🟩 #### Lower perceived heat during exercise in the heat ⭕️ Not Central to Improve Exercise Performance Cooling the palms makes people feel cooler and more comfortable while exercising or resting in hot conditions, a benefit for thermal comfort rather than output. Bilateral palm cooling at 12 °C or 0 °C improved thermal sensation and comfort during cycling at 33 °C ([Iwata et al., 2024](https://pubmed.ncbi.nlm.nih.gov/38382413/)), and a cooling glove lowered heat ratings before a simulated race ([Maroni et al., 2019](https://pubmed.ncbi.nlm.nih.gov/33015244/)). Neither trial found a change in core temperature, sweating or performance, so the benefit is perceptual comfort rather than proven output. **Magnitude:** Thermal sensation ratings were lower than with no cooling, with standardized effect sizes (Cohen's d, the difference in standard-deviation units) of 1.0–2.19 across cooled conditions that included the glove alone ([Maroni et al., 2019](https://pubmed.ncbi.nlm.nih.gov/33015244/)). ### Medium 🟩 🟩 #### Less delayed-onset muscle soreness ⭕️ Not Central to Improve Exercise Performance This bears on post-exercise recovery, not output. Delayed-onset muscle soreness (muscle pain peaking one to two days after hard exercise) was lower after repeated sprints when palmar cooling was used during rest periods. The evidence is a single small placebo-controlled randomized trial in 15 graduate students, with several participants excluded from analyses ([Brown et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40292933/)). The mechanism is unknown; no other trial has measured soreness. **Magnitude:** Soreness ratings 48 hours later averaged 1.83 points lower with cooling than with placebo ([Brown et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40292933/)). ### Low 🟩 #### Faster core-temperature recovery between heat-stress bouts ⚠️ Conflicted ⭕️ Not Central to Improve Exercise Performance It bears on thermal recovery. Resting hand cooling sped core cooling in patent-holding Stanford-group ([Grahn et al., 2009](https://pubmed.ncbi.nlm.nih.gov/19640130/)) and independent ([Kuennen et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20033702/)) trials, as did palm-sole-cheek cooling ([Lissoway et al., 2015](https://pubmed.ncbi.nlm.nih.gov/25771030/)), not others ([Seeley & Sherman, 2021](https://pubmed.ncbi.nlm.nih.gov/33997780/); [Maroni et al., 2018](https://pubmed.ncbi.nlm.nih.gov/29364083/)). On balance, benefit is modest and inconsistent. **Magnitude:** One-hand cooling roughly doubled the rate of core-temperature recovery (0.8 versus 0.4 °C per hour without cooling) ([Grahn et al., 2009](https://pubmed.ncbi.nlm.nih.gov/19640130/)); palm cooling at 10 °C lowered core temperature by 0.38 °C over 50 minutes ([Kuennen et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20033702/)); the null trials found no significant difference in cooling rate versus no cooling. #### Greater resistance-training volume ⚠️ Conflicted Some crossover trials found more repetitions with 1–3 minutes of palm cooling between sets ([Kwon et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20139781/); [Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)); two trials, one double-blind, found none ([McMahon & Kennedy, 2023](https://pubmed.ncbi.nlm.nih.gov/37399240/); [Piñero et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42472446/)). On balance, any effect is inconsistent and partly placebo. **Magnitude:** The two positive trials cited report 22–26% more lifting volume (2,480 versus 1,972 kg, [Kwon et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20139781/)); null trials report no difference. #### Longer endurance ⚠️ Conflicted In crossover trials, a vacuum device extended walking in heat ([Grahn et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15879169/)), hand cooling sped cycling time trials ([Hsu et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15855685/)) and gloves added rowing distance ([O'Brien et al., 2021](https://pubmed.ncbi.nlm.nih.gov/33629973/)); a palm gel pack did not help running ([Scheadler et al., 2013](https://pubmed.ncbi.nlm.nih.gov/23444094/)). Net benefit depends on setting. **Magnitude:** Walking time rose from 32.3 to 46.1 minutes with the vacuum device ([Grahn et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15879169/)); a 30-km cycling time trial was 6% faster ([Hsu et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15855685/)). #### Better repeated sprint and throwing output ⚠️ Conflicted In small crossover trials, palm cooling between bouts increased successful sprints in female athletes ([Wrabley et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40486285/)) and throwing speed in pain-free baseball players ([Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/)), but not interval running ([Walker et al., 2009](https://pubmed.ncbi.nlm.nih.gov/19910808/)). On balance, the signal is small and inconsistent. **Magnitude:** Successful sprints rose from 6.0 to 10.3 per test ([Wrabley et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40486285/)); interval running distance was unchanged ([Walker et al., 2009](https://pubmed.ncbi.nlm.nih.gov/19910808/)). #### Lower heart rate during exercise ⚠️ Conflicted ⭕️ Not Central to Improve Exercise Performance This bears on cardiovascular strain, not output. Palm cooling lowered heart rate after sprints ([Brown et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40292933/)) and during cycling in heat ([Ruddock, Tew & Purvis, 2017](https://pubmed.ncbi.nlm.nih.gov/27494595/)); other trials found no change ([Iwata et al., 2024](https://pubmed.ncbi.nlm.nih.gov/38382413/); [Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)). On balance, any cardiovascular relief is small and inconsistent. **Magnitude:** Heart rate after the second rest interval was about 14 beats per minute lower with cooling than with placebo ([Brown et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40292933/)); other trials found no difference. #### Lower blood lactate ⚠️ Conflicted ⭕️ Not Central to Improve Exercise Performance It bears on metabolic strain. Cooling lowered lactate in hot cycling ([Hsu et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15855685/)) and rowing ([O'Brien et al., 2021](https://pubmed.ncbi.nlm.nih.gov/33629973/)) and sped clearance after leg press ([Caruso et al., 2015](https://pubmed.ncbi.nlm.nih.gov/26038879/)); two trials, one double-blind, found none ([McMahon & Kennedy, 2023](https://pubmed.ncbi.nlm.nih.gov/37399240/); [Piñero et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42472446/)). On balance, effects are inconsistent. **Magnitude:** Blood lactate during submaximal (below maximum effort) cycling in heat was 1.7 versus 2.2 mmol/L with and without cooling ([Hsu et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15855685/)); the double-blind and full-body trials found no difference. #### Lower perceived exertion ⚠️ Conflicted Several crossover trials found lower perceived exertion with palm cooling between sets or throws ([Kwon et al., 2010](https://pubmed.ncbi.nlm.nih.gov/20139781/); [Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/); [Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)); blinded and full-body trials found none ([McMahon & Kennedy, 2023](https://pubmed.ncbi.nlm.nih.gov/37399240/); [Piñero et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42472446/)). On balance, any effect is modest and inconsistent. **Magnitude:** Perceived exertion was lower with 10 °C palm cooling than without in both pain-free and pain-reporting baseball players, with large effect sizes of about 0.75 ([Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/)); the double-blind and full-body palm-cooling trials found no difference. #### Larger long-term strength gains Over weeks of training, palm cooling between sets was linked to large gains in pull-up volume and bench press strength ([Grahn et al., 2012](https://pubmed.ncbi.nlm.nih.gov/22076097/)). The design compared later cooled weeks with earlier uncooled weeks, without a parallel control group, and came from the inventors' laboratory. **Magnitude:** One-repetition maximum (heaviest single lift) rose 22% over 10 weeks, and pull-up volume rose 144% over 6 weeks ([Grahn et al., 2012](https://pubmed.ncbi.nlm.nih.gov/22076097/)). ### Speculative 🟨 #### Protection of muscle from heat-related enzyme failure A proposed mechanism is that cooling keeps working muscle below a temperature at which a key energy enzyme loses activity. The basis is mechanistic and laboratory reasoning only; no human trial has measured it. ## Benefit-Modifying Factors - **Genetic polymorphisms:** No gene variant has been studied as a modifier of palm-cooling response; inherited differences in cold sensitivity or blood-vessel reactivity are plausible but untested. - **Baseline heat strain:** Benefits appear largest when core temperature is already high, as in hot environments or insulating clothing ([Grahn et al., 2009](https://pubmed.ncbi.nlm.nih.gov/19640130/)); in cool rooms and short sets, several trials found no effect. - **Sex:** Women increased bench press volume with both palm cooling and palm heating ([Kwon et al., 2015](https://pubmed.ncbi.nlm.nih.gov/23722108/)) and female athletes completed more sprints ([Wrabley et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40486285/)); most other trials enrolled only men. - **Pre-existing conditions:** In heat-sensitive multiple sclerosis (an autoimmune nerve disease worsened by heat), hand cooling lengthened walking time by about a third ([Grahn et al., 2008](https://pubmed.ncbi.nlm.nih.gov/18474113/)) and lowered heart rate during cycling ([Maguire et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42367317/)). - **Body fat:** Fat insulates the body and speeds overheating, so heat removal through the palms is proposed to matter more in obesity; no PubMed-indexed trial has tested palm cooling in people with obesity. - **Age:** Performance trials enrolled adults mostly under 40. In adults aged 65–89 at rest in heat, hand-and-forearm immersion in 20 °C water eased thermal and heart strain ([Cottle et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40621864/)); performance effects at older ages are untested. - **Cold tolerance:** Baseball players who felt pain during 10 °C cooling threw slower, while pain-free players threw faster ([Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/)). - **Expectation:** A sham immersion raised lifting volume versus control ([Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)), so belief in the method can amplify apparent benefit. ## Potential Risks & Side Effects ### High 🟥 🟥 🟥 #### Cold-induced hand pain and discomfort Cold water or cold surfaces on the hands can cause pain, and pain rises steeply as temperature drops. In baseball players, more than half reported mild-to-moderate pain after 10 °C palm cooling ([Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/)). In a large hand-immersion trial, colder water produced more pain and women tolerated it for less time ([Goreis et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40740425/)). Pain is transient and resolves on rewarming. **Magnitude:** 12 of 22 players (55%) reported pain at 10 °C ([Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/)); at 1 °C only 19% of women tolerated 3 minutes ([Goreis et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40740425/)). ### Medium 🟥 🟥 No risk reaches Medium: the remaining signals rest on post-hoc subgroups (groupings chosen after the data were collected), indirect data from prolonged hand cold exposure or cold pressor testing (hand immersion in ice water that triggers a reflex rise in blood pressure), or pooled general cooling trials, not on consistent palm-cooling trials that recorded the adverse outcome. ### Low 🟥 #### Performance loss when cooling is poorly tolerated In crossover trials, players who felt cooling pain threw more slowly ([Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/)), cooling cut pull-up repetitions in one of three protocols ([Kenville et al., 2024](https://pubmed.ncbi.nlm.nih.gov/39453247/)) and a palm gel pack shortened running time to exhaustion ([Scheadler et al., 2013](https://pubmed.ncbi.nlm.nih.gov/23444094/)). Pain appears to cancel cooling's arousal boost. **Magnitude:** Mean throwing speed fell 4% (101.0 versus 105.2 km/h) in players with cooling pain ([Lin et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40837506/)); running time to exhaustion fell from 46.7 to 41.3 minutes ([Scheadler et al., 2013](https://pubmed.ncbi.nlm.nih.gov/23444094/)). #### Masked heat strain Cooling can make exercisers feel cooler without lowering core temperature, which may encourage pushing harder while overheating continues. Palm or hand cooling alone produced this mismatch in two trials ([Iwata et al., 2024](https://pubmed.ncbi.nlm.nih.gov/38382413/); [Maroni et al., 2019](https://pubmed.ncbi.nlm.nih.gov/33015244/)), consistent with pooled trials of other cooling methods ([Ruddock et al., 2017](https://pubmed.ncbi.nlm.nih.gov/27480762/)). **Magnitude:** Across cooled conditions including a hand-cooling glove alone, thermal sensation ratings were lower than with no cooling (Cohen's d 1.0–2.19) while core temperature did not differ ([Maroni et al., 2019](https://pubmed.ncbi.nlm.nih.gov/33015244/)). #### Reduced hand dexterity and grip control Cold hands lose fine dexterity and over-grip objects, relevant to barbell, racket and throwing tasks. Evidence comes from prolonged immersion studies ([Chen et al., 2010](https://pubmed.ncbi.nlm.nih.gov/21077564/); [Cheung et al., 2008](https://pubmed.ncbi.nlm.nih.gov/18205008/)), not brief palm cooling. **Magnitude:** Finger cooling below 8 °C impaired pegboard dexterity and raised grip force by about 5 N ([Cheung et al., 2008](https://pubmed.ncbi.nlm.nih.gov/18205008/)); the literature reports no outcome figure for 1–3 minute palm-cooling bouts. #### Blood-pressure surge in heart disease Strong hand cold triggers a cold pressor response (reflex rise in blood pressure and heart workload); in coronary artery disease (narrowed heart arteries), cold also cuts heart oxygen supply and can provoke chest pain ([review by Ikäheimo, 2018](https://pubmed.ncbi.nlm.nih.gov/30377633/)). Data come from ice-water tests, not 10–15 °C palm cooling. **Magnitude:** Blood pressure and cardiac workload rise during ice-water hand immersion, and heart oxygen supply falls in coronary artery disease; the literature reports no outcome figure for palm cooling at 10–15 °C. ### Speculative 🟨 #### Cold-sensitivity flares and nonfreezing cold injury Repeated cooling could trigger Raynaud's phenomenon (cold-induced finger blanching) or nonfreezing cold injury (nerve and vessel damage from prolonged cold). No palm-cooling cases exist; the basis is isolated prolonged-cold reports. #### Skin or vessel effects of vacuum devices Subatmospheric pressure around the hand could, in theory, cause swelling or skin marks. No adverse events are reported; the basis is mechanistic only. ## Risk-Modifying Factors - **Genetic polymorphisms:** No gene variant has been studied for palm-cooling risk; familial Raynaud's phenomenon suggests inherited cold sensitivity that could raise pain risk. - **Baseline blood pressure:** Higher resting blood pressure predicts a larger cold pressor rise ([review by Ikäheimo, 2018](https://pubmed.ncbi.nlm.nih.gov/30377633/)), relevant when water is colder than 10 °C. - **Sex:** Women tolerate cold-water hand pain for shorter periods ([Goreis et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40740425/)) and carry higher risk of cold intolerance after cold injury ([Oakley et al., 2022](https://pubmed.ncbi.nlm.nih.gov/35501230/)). - **Pre-existing conditions:** Raynaud's phenomenon, prior nerve injury and smoking raised cold-intolerance risk in cold-exposed athletes ([Oakley et al., 2022](https://pubmed.ncbi.nlm.nih.gov/35501230/)); coronary disease increases cold-related cardiac strain. - **Age:** Older adults have blunted skin blood-flow and cold sensation, so cold injury may go unnoticed; brief 20 °C hand immersion was well tolerated at ages 65–89 ([Cottle et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40621864/)). - **Hot environment:** Exercising in heat raises the stakes of masked heat strain, since feeling cooler does not mean core temperature has fallen ([Iwata et al., 2024](https://pubmed.ncbi.nlm.nih.gov/38382413/)). ## Key Interactions & Contraindications - **Nonselective beta-blockers (heart-rate and blood-pressure drugs; propranolol, nadolol):** Caution. They reduce skin blood flow and cause cold hands, blunting heat exchange and increasing cold pain. Mitigation: the warmer end of the range (14–16 °C), with bouts ended if fingers blanch. - **Anticholinergic drugs (which block sweat-gland nerve signals) and diuretics (which increase urine output) (oxybutynin, amitriptyline, furosemide):** Monitor. They impair sweating or fluid balance, raising heat strain that palm cooling can mask as comfort. Mitigation: heart rate or core temperature tracking. - **Vasoconstricting drugs (sumatriptan, ergotamine, methylphenidate):** Caution. Additive narrowing of hand vessels increases cold pain and reduces heat transfer. Mitigation: no cooling within a few hours of dosing, or water at 14–16 °C. - **Decongestants (pseudoephedrine, phenylephrine):** Caution. Over-the-counter vasoconstrictors raise blood pressure and chill the hands, adding to the cold pressor response. Mitigation: no water colder than 10 °C on dosing days. - **Sedating antihistamines (drowsiness-causing allergy drugs; diphenhydramine, doxylamine):** Monitor. Over-the-counter anticholinergic effects reduce sweating, raising heat strain that cooling may hide. Mitigation: heart rate monitoring in hot sessions. - **Topical anesthetics (numbing creams; lidocaine, benzocaine) on the hands:** Caution. Numbing removes the pain warning, raising cold-injury risk. Mitigation: no application before palm cooling. - **Stimulant pre-workout supplements (synephrine, yohimbine, high-dose caffeine above 400 mg):** Monitor. They raise heat production, heart rate and blood pressure and may constrict skin vessels, adding to heat and cold-pressor strain. Mitigation: moderate doses on hot training days. - **Menthol products (topical gels, menthol mouth rinses):** Monitor. Additive perceptual cooling without core cooling ([meta-analysis by Jeffries & Waldron, 2019](https://pubmed.ncbi.nlm.nih.gov/30554924/)) deepens masked heat strain. Mitigation: objective heat monitoring. - **Nicotine (cigarettes, pouches, vaping):** Caution. Constricts hand vessels and raises cold-intolerance risk ([Oakley et al., 2022](https://pubmed.ncbi.nlm.nih.gov/35501230/)). Mitigation: no nicotine around cooling sessions. - **Other cooling methods (ice vests, neck collars, ice slurry drinks):** Monitor. Effects may add, but combined central and limb cooling was not clearly better than single methods ([meta-analysis by Jiang et al., 2022](https://pubmed.ncbi.nlm.nih.gov/36703929/)). Mitigation: combinations trialled in training before competition. - **Heat acclimation training (repeated heat exposure that builds heat tolerance):** Monitor. Cooling during acclimation sessions lowers the heat stimulus that drives adaptation, possibly slowing it. Mitigation: palm cooling paused during deliberate acclimation blocks. - **Ischemic preconditioning (cuff occlusion before training):** Monitor. Combined with interset palm cooling it raised volume more than preconditioning alone ([Wu et al., 2026](https://pubmed.ncbi.nlm.nih.gov/41668937/)). Mitigation: none needed beyond standard cuff precautions. **Populations who should avoid Palm Cooling:** - Raynaud's phenomenon, primary or secondary (for example with systemic sclerosis, an autoimmune disease that hardens skin and vessels) - Cold urticaria (hives on cold exposure) or cryoglobulinemia (blood proteins that clump in cold) - Peripheral neuropathy (nerve damage that dulls feeling in the hands or feet) with loss of protective sensation (inability to feel a 10-g monofilament, a thin nylon test filament) - Unstable angina (chest pain at rest or rapidly worsening), myocardial infarction (heart attack) within the past 90 days, or uncontrolled hypertension (180/110 mmHg or higher), for water colder than 10 °C - Open wounds, recent hand surgery, or prior frostbite or nonfreezing cold injury of the hands ## Risk Mitigation Strategies - **Temperature control:** Protocols hold the cooling medium at 10–15 °C, checked with a thermometer each session, which prevents cold pain and vasoconstriction-related performance loss. - **Pain stop rule:** Bouts are ended if hand pain exceeds 3 on a 0–10 scale or numbness appears, preventing the performance decrements seen in players with cooling pain. - **Short bouts:** Applications of 1–3 minutes, with total cooling of about 20 minutes per session, reduce dexterity loss and cold-injury risk. - **Rewarm grip before skilled lifts:** Drying the hands and moving the fingers for 10–20 seconds before barbell or throwing sets limits dexterity loss and over-gripping. - **Objective heat monitoring:** In heat, heart rate or core temperature tracking with planned stop criteria guards against masked heat strain, since feeling cooler does not rule it out. - **Cardiovascular screening:** Resting blood pressure below 140/90 mmHg and absence of chest symptoms are checked before water colder than 10 °C is used, reducing cold pressor risk. - **Barrier layer for gel packs:** Freezer gel packs placed inside a glove pouch or thin cloth and allowed to warm to about 10 °C prevent sub-zero skin contact and cold injury. ## Therapeutic Protocol - **Stanford interset protocol:** Palm on a 10–15 °C surface for 2–3 minutes between sets, originally with a vacuum device, now CoolMitt; popularized by Craig Heller ([Grahn et al., 2012](https://pubmed.ncbi.nlm.nih.gov/22076097/)). - **Simple water immersion:** Both hands in 10–15 °C water for 60–180 seconds between sets, as in independent resistance trials ([McMahon & Kennedy, 2023](https://pubmed.ncbi.nlm.nih.gov/37399240/); [Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)). - **Glove gel-pack protocol:** Gloves holding gel packs near 10–11 °C, applied intermittently during rowing intervals; developed by John Caruso's Louisville laboratory ([Soltysiak et al., 2022](https://pubmed.ncbi.nlm.nih.gov/36463544/)). - **Continuous endurance cooling:** Hands immersed in 8–14 °C water during cycling in heat ([Ruddock, Tew & Purvis, 2017](https://pubmed.ncbi.nlm.nih.gov/27494595/)) or a handheld device during walking ([Grahn et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15879169/)). - **Central cooling alternative:** Neck collars, ice vests and cold drinks target the torso and head; a meta-analysis ranks them at least as effective ([Jiang et al., 2022](https://pubmed.ncbi.nlm.nih.gov/36703929/)), and they are an equal-standing alternative. - **Time of day:** No circadian effect is known; timing is set by the session, with cooling during rest intervals and in the hottest part of training. - **Duration of effect:** Not a compound, so no half-life; palm temperature recovers within minutes and any core effect is small and short-lived. - **Single versus split application:** Repeated short bouts between sets or intervals are used rather than one long bout, which risks pain and vasoconstriction. - **Genetic polymorphisms:** No variant is known to change protocol or temperature choice. - **Sex:** Women responded in two trials ([Kwon et al., 2015](https://pubmed.ncbi.nlm.nih.gov/23722108/); [Wrabley et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40486285/)) but tolerate cold pain for shorter periods ([Goreis et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40740425/)), so protocols often start near 15 °C. - **Age:** Older adults tolerated 20 °C hand-and-forearm immersion ([Cottle et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40621864/)); warmer water suits reduced cold sensation. - **Baseline biomarkers:** Higher heat strain (hot room, rising heart rate) predicts more heat to remove; resting blood pressure guides use of water below 10 °C. - **Pre-existing conditions:** Heat-sensitive multiple sclerosis protocols used 18–22 °C surfaces during walking ([Grahn et al., 2008](https://pubmed.ncbi.nlm.nih.gov/18474113/)); Raynaud's phenomenon excludes use. ## Discontinuation & Cycling - **Short-term or ongoing use:** Palm cooling is an acute, session-by-session tool; it can be used indefinitely, seasonally in hot months, or only for key sessions. - **Withdrawal effects:** None are reported; stopping simply returns performance to the uncooled level. - **Tapering:** Not applicable, as there is no physiological dependence to taper. - **Cycling for efficacy:** No tolerance has been documented, so cycling is not needed; alternating cooled and uncooled sessions helps test personal response. - **Heat acclimation blocks:** Pausing cooling during deliberate heat-acclimation sessions preserves the heat stimulus that drives adaptation. ## Sourcing and Quality - **Active vacuum devices:** The Stanford-derived Rapid Thermal Exchanger and CoreControl used circulating cool water with mild vacuum; they were used in early trials and are largely research or legacy equipment. - **Active non-vacuum devices:** CoolMitt, linked to Heller's group, circulates temperature-controlled water; manufacturer performance claims derive from the inventors' own research. - **Passive gloves and packs:** Products such as Tempsicle gloves and NICE Recovery cooling systems use gel inserts or chilled water; starting temperature varies and can fall below 0 °C if frozen. - **Water and thermometer:** A cooler or bucket with water, ice and a digital thermometer reproduces the independent-trial protocols at minimal cost. - **What to look for:** A way to hold 10–15 °C, full palm contact, easy cleaning between users, and no metal or gel surface colder than 0 °C. - **Third-party testing:** Supplement-style testing does not apply; no independent body certifies cooling performance, so thermometer checks are the practical quality control. ## Practical Considerations - **Time to effect:** Any acute effect appears within the same session; claimed strength and volume gains built over 3–10 weeks in uncontrolled data ([Grahn et al., 2012](https://pubmed.ncbi.nlm.nih.gov/22076097/)). - **Common pitfalls:** Using ice water or frozen packs, cooling too long, expecting core cooling during short sets in cool rooms, and judging effect without comparing cooled and uncooled sessions. - **Placebo and expectation:** Sham immersion improved volume in one trial ([Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)), so unblinded personal trials overstate effect. - **Regulatory status:** Consumer cooling devices are sold as general sports products without regulatory review of performance claims; cooling is not a prohibited method under World Anti-Doping Agency rules. - **Cost and accessibility:** Powered devices cost far more than a water container and thermometer, which reproduce most studied protocols. ## Interaction with Foundational Habits - **Sleep:** None direct. No study links palm cooling to sleep; indirectly, lowering heat strain in evening sessions could ease the post-exercise temperature decline before bed. Practical consideration: evening users can monitor sleep quality when adding cooling. - **Nutrition:** Indirect and potentiating. Cold fluids and ice slurry also cool from inside, and dehydration raises heat strain that palm cooling cannot offset. Practical considerations: fluid intake that limits body-mass loss to below 2% per session; cold drinks combined with palm cooling in heat. - **Exercise:** Direct. Cooling is applied during rest intervals; if it raises volume, total training stress and recovery needs rise too. Mechanism is thermal, perceptual or placebo ([Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)). Practical consideration: logging volume and soreness helps match recovery to the added load. - **Stress management:** Indirect. Cold on the hands is a mild stressor that raises arousal and blood pressure ([review by Ikäheimo, 2018](https://pubmed.ncbi.nlm.nih.gov/30377633/)); interset cooling increased arousal markers ([Wu et al., 2026](https://pubmed.ncbi.nlm.nih.gov/41668937/)). Practical consideration: people prone to anxiety may prefer the warmer 15 °C end. ## Monitoring Protocol & Defining Success Baseline testing before starting involves no blood tests. A resting blood pressure reading, a check for Raynaud's phenomenon or reduced hand sensation, and two to three uncooled reference sessions establish the comparison point: repetitions or distance at a fixed load, heart rate at the end of rest intervals, perceived exertion and 48-hour soreness. In hot conditions, a baseline core or ear temperature rise per 10 minutes adds a heat-strain reference. Ongoing monitoring follows a set cadence: the cooling-medium temperature is recorded at every session, and cooled and uncooled sessions are compared at 2 weeks and again at 6 weeks, then every 3 months or at each change of season. Success means a repeatable gain over the uncooled reference without pain; no change after 6 weeks suggests non-response. | Biomarker | Optimal Functional Range | Why Measure It? | Context/Notes | |---|---|---|---| | Cooling-medium temperature | 10–15 °C | Too cold closes palm vessels and causes pain | Digital thermometer each session; frozen gel packs can start below 0 °C, far colder than ice-bath practice suggests | | Resting blood pressure | Below 120/80 mmHg | Cold raises blood pressure | Conventional reference below 130/80 mmHg; seated after 5 minutes of rest, morning, before training | | Core or ear temperature in heat | No established target; track rise per 10 minutes against own uncooled baseline | Shows whether cooling reduces heat strain | Ear readings underestimate core temperature; ingestible sensors are more accurate; best paired with heart rate | | Heart rate at end of rest interval | No established target; compare with own uncooled sessions at the same load | Marks cardiovascular strain | Chest-strap monitor; heat and dehydration raise heart rate | | Training volume load (sets × repetitions × load) | No established target; compare with matched uncooled sessions | Main performance outcome | Alternating cooled and uncooled sessions separates cooling from normal training progress | | Body-mass change across session | Loss below 2% of body mass | Dehydration worsens heat performance | Weighed before and after training, minimally clothed; best paired with urine color | Qualitative markers: - Perceived heat and thermal comfort during sessions - Perceived exertion during sets or intervals - Hand pain, numbness or finger blanching during and after cooling - Muscle soreness 48 hours after hard sessions - Motivation and enjoyment of training ## Emerging Research - **Upcoming heat-strain trial:** [NCT07617649](https://clinicaltrials.gov/study/NCT07617649), a not-yet-recruiting Stanford crossover trial of 30 adults funded by the US National Institutes of Health, will test a hand-cooling table for 10 minutes after treadmill exercise against a cooling bandana, with core body temperature as primary outcome. - **Immune response after exercise:** [NCT07215338](https://clinicaltrials.gov/study/NCT07215338), a completed Stanford trial in 22 participants, tested palmar cooling on immune-cell signaling and delayed-onset soreness after hard exercise; peer-reviewed results are pending, and the sponsor is the inventors' institution. - **Heat acclimation:** [NCT04053465](https://clinicaltrials.gov/study/NCT04053465), a completed University of Connecticut study in 34 participants, examined hand-cooling efficacy across a heat-acclimation period, with internal body temperature as primary outcome. The same group reported that hand cooling sped post-exercise core cooling before, but not after, heat acclimation ([Adams et al., 2017](https://pubmed.ncbi.nlm.nih.gov/27268072/)); trials during exercise could confirm this. - **Repeated sprints:** [NCT06356142](https://clinicaltrials.gov/study/NCT06356142), a completed placebo-controlled pilot of 15 participants measuring sprint times, produced the soreness finding ([Brown et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40292933/)); larger replications could strengthen or overturn it. - **Placebo-controlled designs:** Sham-controlled work found a partial placebo effect ([Wang et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42089765/)); more blinded trials could weaken the case if gains track expectation. - **Null trials in trained lifters:** Full-body training in 25 trained adults showed no benefit ([Piñero et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42472446/)), nor did moderate-intensity bench press ([McMahon, 2024](https://pubmed.ncbi.nlm.nih.gov/38900171/)), challenging the resistance-training claims. - **Clinical and aging populations:** A pilot in multiple sclerosis lowered heart rate during cycling ([Maguire et al., 2026](https://pubmed.ncbi.nlm.nih.gov/42367317/)), and older adults showed less heat strain with hand-and-forearm immersion ([Cottle et al., 2025](https://pubmed.ncbi.nlm.nih.gov/40621864/)); exercise-performance trials in older adults are lacking. - **Spaceflight exercise:** A review proposes palm cooling to limit heat build-up during in-flight exercise on long missions ([Maguire et al., 2025](https://pubmed.ncbi.nlm.nih.gov/39853286/)). - **Combined strategies:** Ischemic preconditioning plus interset palm cooling outperformed sham ([Wu et al., 2026](https://pubmed.ncbi.nlm.nih.gov/41668937/)), opening combination research. ## Conclusion Palm cooling is a simple physical technique: cooling the palms, which hold special heat-releasing blood vessels, during breaks in exercise to draw heat from the body. For health- and performance-minded adults willing to add a small routine to training, the simplest version costs little: a container of cool water and a thermometer. The clearest effect is on how exercise feels: people reliably feel cooler. Trials disagree on whether an overheated body cools faster through the hands at rest. A single small trial suggests less muscle soreness afterward. Claims of large gains in strength-training volume, endurance in the heat and repeated sprints are where the evidence splits: some trials report sizeable improvements, others find none, including one in which neither participants nor researchers knew which treatment was given, and part of the effect appears to come from expectation. The main risks are modest and short-lived: hand pain when the water is too cold, and worse performance in people who find the cold unpleasant. Feeling cooler without actually being cooler can hide a rising body temperature, and strong cold is a concern for people with heart disease or cold-sensitive circulation. The evidence base consists of many small, short studies. Many of the most positive findings come from the Stanford inventors of the patented devices, who have a financial interest in the technology, while independent laboratories report more mixed results. Palm cooling remains a low-risk, low-cost option whose performance benefit is uncertain and appears to vary strongly between people and conditions. **[Top](#top) - [Benefits](#expected-benefits) - [Risks](#potential-risks--side-effects) - [Protocol](#therapeutic-protocol)**