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Alterations of Steroidogenesis by Exercise Countermeasures during Bed Rest (BEDREST0046)
Principal Investigator
Research Area:
Bone and calcium physiology
Muscle physiology
Species Studied
Scientific Name: Homo sapiens Species: Human

The employment of countermeasures specific to the prevention of a set of symptoms resulting from space flight can yield secondary responses that may be deleterious. Heavy exercise has been demonstrated to in part attenuate the adverse effects of space flight on the musculoskeletal and cardiovascular systems. However, heavy exercise can result in alterations in endocrine homeostasis and energy balance. Reports of altered energy balance and endocrine status during space flight have been inconsistent. The investigators have found the incidence of a negative energy balance to be highly space flight mission dependent. The reduction of norepinephrine excretion was also related to mission and was influenced by the gender of the astronaut. These types of inconsistencies are suggested to be due to the excessive workloads during a mission particularly the high levels of exercise required for countermeasures. In physically fit male subjects, investigators have demonstrated a decrease in testosterone levels with excessive exercise. A similar finding of a decrease in testosterone has at times been observed in male astronauts. Females undergoing heavy exercise may develop amenorrhea, the absence of menstruation, associated with a decrease in reproductive steroids. Cessation of exercise rectifies this condition. Reductions in the reproductive hormone estrogen in females and testosterone in male may adversely affect musculoskeletal health and reproductive competence.

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Data Information
Data Availability
Archive is complete. No data sets are available for this experiment. Please Contact LSDA if you know of available data for this investigation.

Body composition
Body mass
Body temperature
Bone mass
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
Campaign 1 08/29/2004 11/21/2004 84 days

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Aeronautics and Space Administration (NASA)
Proposal Source