Key Takeaway
A commercial palm cooling device (BEX Runner) failed to reduce core temperature rise or improve running time to exhaustion in hot conditions, suggesting palm cooling may not benefit steady-state aerobic exercise.
Summary
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.
Methods
- 12 subjects, randomized crossover design
- Time-to-exhaustion runs at 75% VO2max
- 30°C, 50% humidity environment
- BEX Runner palm cooling device vs no device
- Core temperature warmed to 37.5°C before starting
- Heart rate, RPE, mood, and core temp recorded every 2 minutes
Key Results
- Control: 46.7 ± 31.1 min to exhaustion
- Palm cooling: 41.3 ± 26.3 min (significantly worse, p<0.05)
- Core temp rise: 0.047 vs 0.048°C/min (no difference)
- No attenuation of core temperature rise with device
Limitations
- Used a commercial device (BEX Runner) rather than lab-grade equipment with subatmospheric pressure
- Running involves arm swing which may reduce palm contact with the device
- Does not disprove the palm cooling mechanism, only this specific implementation