Dynamics of physical performance during long-duration space flight (first results of "Countermeasure" experiment).

The efficacy of countermeasure exercise for diminishing disturbances induced by microgravity in motor system and its visceral supply during different stages of long-duration flight was evaluated. The results of both bicycle and locomotor testing indicate that physical fitness of cosmonaut does not become worse in the course of the long-duration flight. On the contrary, the lowest fitness was recorded at the first stage of mission, just after one month of flight. The "dead period" at the beginning of space flight seems to be a manifestation of the acute decrease in physical condition on transition from 1 G to microgravity, when none of the regular countermeasure regimes is sufficiently effective and acute increase of volume and intensity of training is impossible under the conditions of space flight.