From the football turf to high above the Earth, heat exhaustion is a life-threatening concern. Heat exhaustion, or hyperthermia, is an acute condition caused by excessive exposure to heat and dehydration. It occurs when the body can no longer dissipate heat adequately because of extreme environmental conditions or increased heat production from within. Heat exhaustion may progress to heatstroke when the body’s thermoregulatory mechanisms become overwhelmed and fail, ultimately leading to brain and organ damage or even death.
In football, heat exhaustion is a dangerous reality. Football players take the field for preseason training during the dog days of summer, frequently in full pads, when the heat index can easily exceed 100 °F. On top of all the pads and the sweltering heat—or underneath, to be more precise—are players who weigh over 300 pounds. In fact, there are more than 300 players in the National Football League (NFL) topping 300 pounds. Due to their body mass, these players, who generally serve as offensive and defensive linemen, face a high risk of suffering from heatstroke. Even players in top shape can be at high risk for a variety of reasons, including if they quickly shed pounds to meet stringent weight requirements (a practice known as “cutting weight”), or if they reach critical dehydration because they sweat out fluids without properly replenishing.
In space, astronauts on extravehicular activity assignments are constantly exerting themselves, which can cause rapid increases in body temperature. Although the space suit is insulated to keep astronauts comfortable from the extreme temperatures of space—the side of the suit facing the Sun may reach temperatures as high as 250 °F, while the opposite side, exposed to the darkness of deep space, may reach temperatures as low as -250 °F—astronauts still release body heat and humidity inside the suits, which could lead to heat exhaustion and eventually heatstroke.
In order to monitor the body temperature of astronauts during space flight, NASA teamed up with Johns Hopkins University in the late 1980s to develop an ingestible “thermometer pill” called the Ingestible Thermal Monitoring System. Incorporating a number of space technologies, including wireless telemetry (wireless signal transmission), microminiaturized circuitry, sensors, and batteries, the thermometer pill became commercially available in research, university, and military markets in 1988 (Spinoff 1994). Due to a heightened awareness of heatstroke risk among athletes, brought on by the deaths of a professional football player and a college football player just a week apart in 2001, the product is now well received as a means to detect elevated core body temperature during sporting activities.
Under a $75,000 grant from NASA, the Johns Hopkins University Applied Physics Laboratory worked closely with Goddard Space Flight Center to develop the Ingestible Thermal Monitoring System. The resulting ¾-inch capsule consisted of a silicone coating on the exterior and a telemetry system, a microbattery, and a quartz crystal temperature sensor on the interior.
Once ingested and inside the gastrointestinal tract, the quartz crystal sensor vibrates at a frequency relative to the body’s temperature, producing magnetic flux and transmitting a harmless, low-frequency signal through the body. This signal can then be retrieved by a recorder, outside of the body, that displays the core body temperature reading with an accuracy to within one-tenth of a degree, Celsius.
The temperature-reading pill was first put to use by a Johns Hopkins University veterinarian named Dr. Phillip Brown, who monitored an animal’s temperature during and immediately following surgery. Brown noted that large animals can be erratic and dangerous while coming out of anesthesia; with the capsule, “doctors can monitor animals from a safe distance.”