Comparison of actual and imagined execution of whole-body movements after a long exposure to microgravity.

Five cosmonauts were tested 30 days before a six-month space flight and also on the 2nd and the 6th day after their return to Earth. Cosmonauts performed and imagined a task that involved climbing two stairs to step onto a platform, jumping down with both feet and walking normally for a distance of 4 m. Durations of actual and imagined movements were measured by an electronic stopwatch. Results indicated that cosmonauts performed actual and imagined movements with similar durations before and after the space flight. However, the 2nd day after their return to Earth, cosmonauts significantly increased the durations of both actual and imagined movements. The durations of the imagined and actual movements returned to approximate pre-flight values 6 days after landing. Our results provide evidence that motor imagery process accurately replicates the neural and mechanical modifications which occur during the re-adaptation of the motor system on Earth's gravito-inertial environment after a long space flight.