Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment.
Level 3 - non-randomized controlled study
Controlled crossover laboratory trial with unstated randomization in abstract
PubMed 15879169 · doi:10.1152/japplphysiol.00093.2005
What was done
Subjects performed uphill treadmill walking (5.63 km/h) in a 40 °C environment under paired conditions with and without a palm-cooling device combining local subatmospheric pressure (35–45 mmHg) and a palmar heat sink (18–22 °C). Sub-experiments measured esophageal temperature rise (n = 8), exercise duration (n = 18), cooling alone versus combined cooling and negative pressure (n = 6), and an 8-week protocol with varied weekly workloads across 2 to 4 trials per week (n = 9).
What was found
Palmar heat extraction with subatmospheric pressure reduced the esophageal temperature rise rate compared to control (2.1 ± 0.4 vs. 2.9 ± 0.5 °C/h, n = 8) and extended exercise duration from 32.3 ± 1.7 to 46.1 ± 3.4 minutes (n = 18). Hand cooling alone had little effect on duration compared to control (38.0 ± 3.5 vs. 34.1 ± 3.0 min), whereas combined cooling and subatmospheric pressure increased duration to 57.0 ± 6.4 minutes (n = 6). In the 8-week protocol (n = 9), performance improved across all workloads, but the proportional benefit decreased at higher workloads.
Why it matters
This study shows that applying negative pressure alongside palmar cooling enhances heat extraction from circulating blood, attenuating core temperature rise and extending exercise endurance in extreme heat.
Limits
Sample sizes across the sub-experiments were small (n = 6 to 18). The abstract does not indicate whether trial order was randomized or blinded, does not report participant demographics, and only tested treadmill walking.
Cited by
- supports Palmar cooling lowers core body temperature before exercise as a method to increase and prolong exercise effort.