General results of the 21-day head-down bedrest study without the use of countermeasures

The paper reports the major results of an IBMP bedrest study with the emphasis on its preparation and implementation. The study involved 12 healthy males (29.8 ± 4.6 years of age, M ± SD) volunteered for a 21-d head-down bed rest at –6° (HDBR). Body length, mass and water balance were measured daily (2 days prior, during and in 2 days after HDBR). Routine checkups were performed twice a day. They included heart rate (HR), blood pressure(BP) and temperature measurements, and recording complaints, if any. Data analysis pointed to a tendency for body elongation and mass loss in the period of acute adaptation; these changes retained till the end of HDBR. Water balance was noted to be negative during HDBR but became positive on completion. HR, BP and body temperature were decreased in the early HDBR period and increased significantly on the first day after its completion. The most common complaints were about back discomfort, generally inthe lumbar region.