Key Takeaway
Bilateral palm cooling at 12°C and 0°C improved thermal sensation and comfort during exercise at 33°C but had no effect on core temperature, sweating, or cardiorespiratory function in 10 active men.
Summary
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.
Methods
Randomized crossover design with 10 active men. Three conditions: bilateral palm cooling at 12°C, bilateral palm cooling at 0°C, and control (no cooling). Cooling was applied before and during 20 minutes of exercise at 33°C, 60% relative humidity. Measurements included rectal temperature, skin temperature, heart rate, local sweat rate, oxygen uptake, CO2 production, respiratory exchange ratio, RPE, thermal sensation, and thermal comfort.
Key Results
Thermal sensation and thermal comfort were significantly improved in both ICE12°C and ICE0°C conditions compared to control. ICE0°C produced longer duration of cold sensation than ICE12°C. No significant differences between conditions for rectal temperature, skin temperature, heart rate, local sweat rate, oxygen uptake, CO2 production, or respiratory exchange ratio.
Limitations
Small sample size (n=10) with only male participants. Short exercise duration (20 minutes) may not capture effects during prolonged endurance exercise. Moderate exercise intensity may not generate sufficient thermal strain. No performance outcome measures were assessed (only physiological and perceptual). Laboratory setting may not fully replicate real-world hot environment conditions.