The SIRIUS-21 study was designed as a 240-day isolation of healthy volunteers in controlled environment simulating a piloted mission to the Moon including operator's activities in lunar orbit and on the surface. The investigation involved an international crew of two women and 3 men at the age of 29 to 44 years. The object was metabolic reactions of healthy bodies to the simulated conditions. Crew members demonstrated a moderate stress reaction characterized by inhibition of the gastrointestinal tract secretory activity, reduction of glycolysis intensity, persistent hypercalcemia, a more intensive creatine kinase system functioning as a buffer, deficit of macroergic compounds, magnesium and essential microelements. On day 7 post isolation, the stress symptoms showed a partial leveling. Hard physical training had both the positive and negative effects on metabolism dynamics. The preventive purpose of training was to normalize the content of essential microelements in blood and suppress atherogenesis; however, training had also the negative effect of inducing hypohydration. In future isolation studies it would be appropriate to optimize training protocols and enhance the program of countermeasures to the negative effects of simulated factors.