OBJECTIVES:
This experiment investigated the circadian rhythm of core temperature and the thermoregulatory and cardiovascular adaptations during rest and exercise in the course of a long-term microgravity exposure on the International Space Station (ISS). The data derived might be important not only to understand human adaptation in space in view of the thermoregulatory and cardiovascular system, but as well as associated to problems dealing with body weight loss and de-synchronization of internal rhythms which affect the overall health and performance of astronauts/cosmonauts.
Measuring core body temperature is not straightforward because a thermometer must be placed close to the heart for best results. Many types of thermometers exist, from the type that goes under the tongue to the type that goes into the ear, but unfortunately the most accurate way of reading a core temperature is inserting a thermometer in the rectum. Body temperature tends to be lower in the feet and lowest in the early morning hours between four and six.
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APPROACH:
As part of this experiment, a total of 11 astronauts took their temperatures using Thermolab, an instrument developed by Dr. Hanns-Christian Gunga, of the Center for Space Medicine and Extreme Environments in Germany. The Thermolab sensor is non-invasive, and can be read from a distance, making it a valuable tool for astronauts working in space. It makes use of two sensors — one attached to an astronaut's head, the other to his or her chest. Mission controllers on the ground were able to monitor the astronauts' temperatures as they continued working on the ISS. This experiment was performed in conjunction with the NASA sponsored VO2max study. Astronauts wore the Thermolab hardware while performing the VO2max study protocol.
RESULTS:
This experiment shows that an astronaut's temperature rises by one degree Celsius during the first two months on the ISS and remains there until it drops back to normal on return to Earth. Comparing data to other studies shows a correlation with Interleukin-1, a hormone that causes fever when sick. Raising body temperature by a degree requires 20% more energy, derived from food, so mission planners need to know more about this phenomenon in order to estimate the required food supplies for long-duration missions.