Whether you’re planning a short day hike or a multi-day backpacking trip, one challenge you will always face is how to regulate your body temperature. If you’re too cold, you’ll be miserable and could even be at risk for hypothermia. If you’re too hot, you’ll sweat excessively and risk dehydration, as well as hypothermia from your wet clothes once you stop moving. Often, we utilize layered insulation, wind shirts, and other gear to help with this problem. We also increase our fitness and decrease our exertion rate to avoid sweating. Some situations even call for vapor barriers to mitigate sweat soaking our clothing. In this article, we’ll explore a novel strategy for managing body heat: using your palms.
Craig Heller, a professor of biology at Stanford University, has studied the effects of cooling the palms on athletic performance. His work has shown that cooling the palms can help reduce core body temperature and improve performance in hot environments. When we are exposed to heat, the blood flow in glabrous skin (hairless areas of our skin such as the face, the palms of our hands, and the soles of our feet) can be up to 10 times higher than in other areas. The palms have the added advantage of being easily accessible, even when bundled up. Dr Heller has researched how to use this fact to cool off people in heavy, insulating clothing1, such as firefighting gear, body armor, and COVID-19 personal protective equipment. His lab has also researched how cooling the palms during exercise in a hot environment can help us reduce how quickly our body temperature increases and help us perform better physically.
While most of our concern about high body temperature comes from trying to limit sweating, high temperature in a muscle reduces that muscle’s ability to produce force. As we exercise, our muscles heat up, and our body disperses that heat throughout the body by circulating our blood. The unique blood flow of our glabrous skin allows cooling of the palms to lower the temperature of the circulating blood much faster than cooling any other part of the body.
Of course, cooling too fast can be very dangerous. The blood vessels so vital to radiating excess heat out of the body will rapidly constrict if in contact with something pulling heat out of the body too quickly. Therefore, plunging your hand in ice water has significantly less of a cooling effect than submerging your palm in cool water, between 45 and 60 degrees fahrenheit. Heller and his colleagues have developed a device and protocol to efficiently cool the palms, which shows striking performance enhancement capabilities.