Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment
Grahn, D. A., Cao, V. H., & Heller, H. C. (2005). Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment. In Journal of Applied Physiology (Vol. 99, Issue 3, pp. 972–978). American Physiological Society. https://doi.org/10.1152/japplphysiol.00093.2005
Introduction: In situations where the accumulation of internal heat limits physical performance, enhanced heat extraction from the body should improve performance capacity.
Methods: The combined application of local subatmospheric pressure (35–45 mmHg) to an entire hand (to increase blood volume) and a heat sink (18–22°C) to the palmar surface were used to draw heat out of the circulating blood. Subjects walked uphill (5.63 km/h) on a treadmill in a 40°C environment. Slopes of the treadmill were held constant during paired experimental trials (with and without the device).
Results: Heat extraction attenuated the rate of esophageal temperature rise during exercise (2.1 ± 0.4° and 2.9 ± 0.5°C/h, mean ± SE, with and without the device, respectively; n = 8) and increased exercise duration (46.1 ± 3.4 and 32.3 ± 1.7 min with and without the device, respectively; n = 18). Hand cooling alone had little effect on exercise duration (34.1 ± 3.0, 38.0 ± 3.5, and 57.0 ± 6.4 min, for control, cooling only, and cooling, and subatmospheric pressure, respectively; n = 6). In a longer term study, nine subjects participated in two or four trials per week for 8 wk. The individual workloads (treadmill slope) were varied weekly. Use of the device had a beneficial effect on exercise endurance at all workloads, but the benefit proportionally decreased at higher workloads.
Conclusions: It is concluded that heat can be efficiently removed from the body by using the described technology and that such treatment can provide a substantial performance benefit in thermally stressful conditions.
Keywords: arteriovenous anastomoses, venous plexus, aerobic capacity, cardiac drift, heat stress
In Simple Terms:
This study tested a device that cools the palm while applying gentle vacuum pressure to help remove heat from the body. In a hot environment, using the device slowed down the rise in core temperature and allowed people to exercise longer (up to 46 minutes compared to 32 without it). Over 8 weeks, it consistently improved endurance during heat-stress workouts, especially at lower intensities.
Uploaded by Braeden Ostepchuk, creator of the CEU-approved course 0th Law of Physiology, co-founder of Kuhler Technologies, and inventor of Kühler.