Microgravity: an ideal environment for cardiac force measuring

In the article main principles of ballistocardiography are considered. Special attention is paid to registration of the spatial ballistocardiogramm. There exist two principles of ballistocardiography: dynamic and seismic. In the event of dynamic ballistocardiography body displacements align to an extent with shifting of the general center of body gravity. Ideal conditions for ballistocardiogram acquisition could be reached if rigidity of internal body relations had an infinitely large value, while rigidity of external relations was nearing the zero. Then displacements of the entire body would depend only on the forces imparted by the cardiovascular system. Microgravity is the only environment providing these ideal conditions for ballistocardiography. Microgravity allows effective application of the dynamic BCG principle to recording pulse-induced body movements corresponding to the center of mass displacements. This kindled interest of the first researchers in space medicine in ballistocardiographic investigations during space flight. Since free flying requires enough space, the investigations became possible only with construction of orbital stations. The first in-space ballistocardiogram was recorded on December 26, 1977 from Yu. Romanenko, commander of the first expedition to the Russian OS Salyut-6. The data about ballistocardiographic researches at orbital stations Salyut and MIR which were conducted to 70-90th years is presented. The first attempt the spatial ballistocardiogramm registration has been made in 1984 during the Soviet - Indian flight on OS Salyut-7. The first records spatial ballistocardiogramm have been made during space experiment "Vector" on OS the MIR in 1990. New experiment "Cardiovector" on the ISS is being prepared for 2014-16.