Human thermohomeostasis onboard "Mir" and in simulated microgravity studies

Area of Science:

• Space physiology
• Human thermoregulation
• Environmental medicine

Background:

• Ground-based simulations like bed rest and suit immersion (SI) are used to study microgravity effects.
• These simulations showed a downward trend in rectal temperature.
• Previous studies indicated potential changes in thermoregulation during spaceflight.

Purpose of the Study:

• To investigate the effects of microgravity on human thermoregulation.
• To compare in-flight body temperature changes with ground-based simulations.
• To determine if thermoregulation is significantly altered during long-duration space missions.

Main Methods:

• Autothermometric measurements were conducted onboard the
• Mir
• space station over 2-174 flight days.
• Two flight engineers participated, with prior testing using suit immersion (SI).
• Thermotopometric methods were employed to simulate microgravity effects.

Main Results:

• In-flight rectal temperature was higher compared to normal terrestrial conditions.
• Microgravity was identified as the key factor for increased human body surface temperature.
• The external/internal temperature gradient was abolished in spaceflight.
• Thermoregulation (T-homeostasis) remained largely unchanged, suggesting an acute microgravity effect.

Conclusions:

• Microgravity causes an increase in body surface temperature and eliminates the temperature gradient.
• Rectal temperature is expected to be higher in spaceflight than on Earth.
• Thermoregulatory homeostasis is maintained, but exhibits acute responses to microgravity.
• Further consideration of excess entropy in the human body is warranted.