The article is devoted to the assessment of force and energy characteristics of the heart muscle in microgravity using the method of spatial ballistocardiography. The studies were conducted with the participation of Russian cosmonauts who performed space flights of various durations. Physiological signals were recorded using the Cardiovector device. The experiment was carried out twice before the flight, monthly during the flight, and also on days +3–4 and +7–8 after return to Earth. It has been shown that the force of cardiac contraction does not change significantly, but the energy decreases, which can be explained by the principle of economizing the work of the heart under space flight conditions. Mission extension does not lead to significant energy reduction to levels that could indicate possible signs and risks of energy deficiency. [ABSTRACT FROM AUTHOR]