It was hypothesized that heat balance, thermoregulation and circadian temperature rhythms were altered in humans during long-term space flights because of changes in i) the natural convective heat transfer from the body surface to the environment, ii) fluid shifts along the body axis from peripheral to central parts, iii) the cardiovascular and iv) the autonomous nervous system as well as v) due to changes of body composition (fat mass, muscle mass, body water).
Since these factors were particularly cross-linked with each other during exercise, an integrative study of the topic under microgravity conditions is mandatory. However, such integrative studies combining exercise performance (NASA’s VO2max experiment) and thermoregulatory adaptations of humans in space have been very limited to date or even missing for long-term space flights due to methodological constraints. Therefore, this proposal aimed to investigate the core temperature and heart rate during rest and exercise to determine the physiological strain index (PSI) in the course of a long-term bed rest.
For this purpose a newly developed thermo-sensor (Double Sensor™, Draegerwerk AG) for core temperature was applied. This technical device would study non-invasive and very convenient to the subject the core temperatures during rest and exercise under long-term bed rest conditions.
As an outlook, these technological developments would be used for daily life applications on Earth (“spin-offs”) such as the core temperature monitoring devices for humans working in extreme environments (fire fighters, Special Forces) and newborns.
During space flight, crewmembers are (1) frequently exposed to hot or cold environments, (2) have to perform high physical workloads (3) must wear heavy armor protective clothing against cold stress or radiation during EVA’s. Under these conditions the body core temperature can change rapidly, eventually reaching deleterious levels. Until now, body core temperatures measurements were quite difficult to achieve, and required insertion of a thermo sensor into the body. The Double Sensor™ hardware would allow the first time to monitor body core temperature during long-duration space flight, and will lead to a better understanding of heat transfer in humans under microgravity conditions.
The information obtained by this study should lead to a better basic understanding of heat transfer and thermal regulation in humans during long-term bed rest and serves as a comparative study in regard to the Thermolab experiment which is performed during long-term ISS missions.
This experiment has concluded in ground-based studies sponsored by the National Aeronautics and Space Administration's Human Adaptation and Countermeasures Division. This experiment was conducted during the Head Down Tilt 30 Day (HDT30) Study. LSDA does not expect to receive results from this study.
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