During ballistic descent from the International Space Station, cosmonauts are subjected to overloads of up to 8 g, which means that at certain moments the human body feels a weight approximately eight times greater than normal.
Such loads are considered acceptable, but they require strict training and medical supervision. An important factor is not only the magnitude of the overload, but also its direction: transverse loads from chest to back and longitudinal loads from head to pelvis affect blood circulation, the functioning of internal organs, and overall well-being in different ways.
To test the crew's resilience to such conditions, cosmonauts are examined annually on centrifuges. In the chest-to-back mode, overloads of 4 g for 60 seconds and 8 g for 30 seconds are simulated; in the head-to-pelvis direction, 3 g and 5 g are simulated for 30 seconds each.
The total duration of the procedure reaches one hour and makes it possible to ensure that cosmonauts are ready for extreme return-to-Earth scenarios.