Controlled heat transfer with mammalian bodies: In the 1990s Stanford University biologists Dennis Grahn and H. Craig Heller discovered a novel way of treating patients with a condition known as postanesthetic hypothermia, in which patients emerging from anesthesia are so cold that they shiver for up to an hour. The condition develops in part because anesthesia reduces the body’s ability to control its own temperature. Applying heat alone does not always help, so Grahn and Heller tried another approach: they increased the volume of blood flowing to the skin of patients’ hands and then applied heat to the same area. “These people were fine within 10 minutes,” Grahn says. “Then the question was, ‘What the heck is going on here?’”

They had stumbled on a feature of mammalian biology that can be manipulated for a wide array of other applications, including ones requiring cooling. Among these uses is increasing athletic endurance, because overheating is one of the primary factors limiting physical performance. One of the main ways the human body regulates internal temperature is by controlling the amount of blood flow through nonhairy skin areas, such as the palms, the cheeks, the nose and the soles of the feet. Underneath the skin of these areas are unique vascular structures designed to deliver large volumes of blood to the surface. When the body needs to release heat, it expands these vessels and floods the area with blood, throwing off heat through the skin. The body holds in heat by constricting blood flow to these areas.

Patent No. 7,947,068 outlines a variety of ways to manipulate these processes. One, called the Glove, is already in use by the San Francisco 49ers. Players stick their hand into the coffeepot-size device, which creates an airtight seal around the wrist. The Glove then uses a pressure differential to draw blood to the palm and rapidly cool it, which leads to an overall decrease in body temperature. The device can be used at any point during a game and takes only a few minutes to work. Tests in the lab, Grahn says, have shown that devices like the Glove can dramatically increase athletic output and reduce heat stress.