Human sensorimotor coordination following space flights.
Studies have been carried out 18-30 days before the flight and on the second day after landing. The recovery kinetics of cosmonauts who completed the 18-day space flight was followed for 30 days after their return. Muscle tone, indices of muscle strength and parameters of the functions of the extremities were examined, and the ability to maintain vertical posture was studied (stabilography). Flights of short duration did not cause any serious disturbances in the neuromuscular system. Together with this fact, the analysis of the results revealed a certain regularity in the physiological effects as reflected by a decrease in the strength of the torso extensors and the muscle tone of the lower extremities, The tone and strength of the arms altered insignificantly, and the alterations were not an indication of muscular atrophy. Stabilographic studies showed a decrement in the stability of the vertical posture of the cosmonauts. The above alterations were particularly pronounced in the crew members of Soyuz 9. As distinct from the previous flights of the Soyuz spaceships the crew members of Soyuz 9 showed normality in the regulation of vertical posture only on the tenth day after the flight. One of the reasons for the above alterations in postural regulation may be the decrease in muscle tone noted repeatedly after both of the previous space flights and in experiments with simulation of separate effects of weightlessness. Another reason for the deterioration in postural regulation is probably the changes in interaction between the neutral analysers. A possible reason for the apparent defects in stability may be the disturbance of the interaction between various muscle groups, i.e. the disturbance in synergism which is required for the maintenance of vertical posture. Similar alterations were observed in people who had been subjected to bed rest for a long time. Readaptation to the ground environment appeared to proceed in stages. The comparative evaluation of post-flight findings showed that prolonged periods of flights up to 18 days resulted in more pronounced alterations in human sensomotor coordination.