PAST EXPERIENCE INDICATES THAT HUMAN STAY IN WEIGHTLESSNESS DURING SPACE FLIGHT INDUCES SOME CHANGES IN THE ASTRONAUT'S BODY FUNCTIONS. THESE CHANGES BECOME ESPECIALLY NOTICEABLE AFTER RETURN TO EARTH GRAVITY CONDITIONS. HOWEVER, THESE CHANGES ARE REVERSIBLE. IN ORDER TO PREVENT THE DECONDITIONING OF THE ORGANISM IN ZERO GRAVITY, CERTAIN COUNTERMEASURES ARE TAKEN. CERTAIN PROTECTIVE TECHNIQUES CAN BE USED TO FACILITATE THE READAPTATION OF THE HUMAN BODY AFTER LANDING ON EARTH.