Figure 3: Hypothetical mechanism for the development of adaptive responses of skeletal muscle fibres and cardiomyocytes to the change in mechanical conditions. An increase in the external mechanical load on the cardiomyocytes in early stages of antiorthostatic disuse in rats should naturally cause an increase in the cell’s ability to resist it, that is, an increase in cell stiffness and development of the cytoskeleton, in addition to an intensification of the cell respiration. Decrease of the load on the rat skeletal muscle fibres during antiorthostatic disuse does not require the development of the cortical cytoskeleton, and as a result the cell’s stiffness should decrease. Hypothetical links are shown by dashed arrowheads and contours. −/+: decrease/increase in protein content, from the left/to right—for load/disuse.