Palmar Cooling Research

This study investigated the effects of intermittent palm cooling (PC) and sole cooling (SC) on acute training volume during resistance exercise. Three separate randomized crossover protocols were conducted with 41 healthy, physically active adults (12 female, mean age 23.9 years). The protocols tested commonly practiced bodyweight and machine exercises: pullups, pushups, and leg extensions.

Contrary to the proposed ergogenic benefits of palmar cooling, the results were largely null. Palm cooling actually led to significantly fewer total repetitions during pullups compared to no cooling (p < 0.001). Neither pushups nor leg extensions showed any benefit from palm or sole cooling. Additional measurements during the leg extension protocol — tympanic temperature, rate of perceived exertion, and quadriceps EMG — were also unaffected by sole cooling.

The authors conclude that intermittent palm and sole cooling have limited effectiveness for enhancing training volume during resistance exercise in physically active adults, and call for future research under more controlled conditions with comprehensive physiological measurements.

This study examined whether interset palm cooling could enhance performance during moderate-intensity resistance exercise. Nine healthy, resistance-trained subjects (7 male, 2 female, mean age 22 years) performed 4 sets of bench press to failure at 60% of their 1 repetition maximum with 3-minute passive recovery between sets.

In a randomized crossover design, subjects completed either a cooling condition (2 minutes of palm cooling at 10°C between sets) or a control condition (passive rest) separated by one week. While the cooling intervention successfully reduced palm temperature compared to control (p < 0.001), it failed to translate into any performance or physiological benefits.

No significant differences were found between conditions for volume load, repetitions, barbell velocity, muscle activation, blood lactate, or rate of perceived exertion (all p > 0.05). The authors conclude that palm cooling does not enhance acute moderate-intensity resistance exercise, suggesting its proposed ergogenic effects may be limited to high-intensity or heat-stress contexts.

This study investigated whether bilateral palm cooling before and during exercise in a hot environment (33°C, 60% relative humidity) could improve thermoregulatory and subjective indicators. Ten active men (mean age 21 years) completed three randomized trials: palm cooling at 12°C (ICE12°C), palm cooling at 0°C (ICE0°C), and a control condition with no cooling.

After 30 minutes of rest at ambient temperature, participants exercised for 20 minutes in the hot environment. The key finding was that palm cooling at both temperatures significantly improved thermal sensation and thermal comfort compared to the control condition. The 0°C cooling produced a longer duration of cold sensation than the 12°C cooling, suggesting a dose-response relationship with temperature.

However, none of the objective physiological measures — rectal temperature, skin temperature, heart rate, local sweat rate, oxygen uptake, carbon dioxide production, or respiratory exchange ratio — differed between conditions. This suggests palm cooling primarily acts on perceptual rather than physiological pathways during moderate exercise in heat, and that even very cold temperatures (0°C) can be safely applied to the palms without adverse vasoconstriction effects on comfort.

This study extended palm cooling research to women, testing whether cooling (10°C) or heating (45°C) the palms between sets of resistance exercise could delay fatigue. Eight trained women (6±2 years experience) performed 4 sets of bench press at 85% 1RM to failure with 3-minute rest intervals under three conditions.

Both cooling and heating increased total volume load compared to thermoneutral control. The cooling condition produced 1,387±358 kg total volume vs 1,187±262 kg for control — a 17% increase. Palm cooling specifically outperformed control during set 2, while heating showed benefit in set 4.

The authors interpret the results through central governor theory: thermal input from the palms may modify the brain's perception of fatigue risk, allowing greater motor unit recruitment regardless of the direction of temperature change.

This study tested whether a commercial palm cooling device could improve running performance in hot conditions. 12 subjects ran at 75% VO2max in 30°C/50% humidity until exhaustion, with and without the BEX Runner device.

Palm cooling did not help — and actually slightly hurt performance. Control runs lasted 46.7 minutes vs 41.3 minutes with cooling (significantly worse). Core temperature rise was virtually identical between conditions (0.047 vs 0.048°C/min), meaning the device failed to extract meaningful heat during running.

This contrasts with Grahn's positive findings and likely reflects a device limitation: the BEX Runner may not apply adequate contact pressure or cooling power compared to the Stanford lab's subatmospheric pressure device. The result highlights that not all palm cooling approaches are equal — the mechanism requires maintaining blood flow through the palm's AVAs, which cheap devices may not achieve during the motion of running.

This Stanford study demonstrated the remarkable effects of palm cooling on training capacity. Subjects who used palm cooling between sets of pull-ups were able to perform dramatically more volume over a 6-week training program.

The cooling group increased their total pull-up volume by 144% compared to a passive rest control group. More importantly, this increased training volume translated to greater strength gains - the cooling group nearly tripled their initial pull-up capacity while controls only doubled theirs.

This study established that heat is often the limiting factor in training and that cooling the palms is an efficient way to extract core heat.

This foundational study from the Stanford palm cooling lab quantified heat extraction rates through glabrous (hairless) skin surfaces — the palms, soles of the feet, and face. These regions contain specialized blood vessels called arteriovenous anastomoses (AVAs) that allow rapid heat transfer between core blood and the environment.

Subjects exercised in 41.5°C heat wearing insulating gear until core temperature exceeded 39°C, then recovered for 60 minutes with various cooling treatments. Without cooling, temperature dropped 0.4°C/h. Cooling one hand achieved 0.8°C/h, and adding subatmospheric pressure improved it to 1.0°C/h. Cooling multiple glabrous surfaces was additive — face + feet + hands together achieved a 1.6°C drop.

The study clarified that subatmospheric pressure doesn't increase heat transfer per se, but maintains blood flow through the AVAs by preventing local vasoconstriction from the cold stimulus. This is why simply holding an ice cube doesn't work as well — the cold causes vasoconstriction, reducing blood flow and heat exchange.

This Stanford study tested whether extracting heat through the palm could improve aerobic endurance in hot conditions. Subjects walked uphill on a treadmill at 5.63 km/h in a 40°C environment with and without a palm cooling device that applied mild subatmospheric pressure (35-45 mmHg) combined with a cold surface (18-22°C).

With palm cooling, subjects lasted 46.1 minutes vs 32.3 minutes without — a 43% improvement. Core temperature rise was significantly reduced (2.1 vs 2.9°C/h). The subatmospheric pressure was critical: cooling the hand alone without negative pressure provided minimal benefit, because the pressure is needed to keep blood flowing through the glabrous skin of the palm.

An 8-week follow-up with 9 subjects confirmed the benefit was consistent across sessions and workloads, with proportionally greater effects at lower exercise intensities.