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This paper presents the results of studying the vestibular function before and after space flight in response to separate and combined vestibular, optokinetic, proprioceptive and postural tests as well as cerebellar coordination tests. After prolonged space flights most crewmembers showed spontaneous, position and positional nystagmus that pointed to vestibular dysfunction. This integrated procedure made it possible to differentiate mechanisms of vestibular dysfunctions seen after flight: some subjects showed nystagmus responses only during tilt table tests while others displayed them in response to additional proprioceptive and optovestibular stimulation as well as cerebellar coordination tests. Different patterns and types of vestibular adaptation to gravity were identified.

The objective of medical investigations during and after the 366-day manned mission was to accumulate information about human responses to long-term effects of microgravity. To do this, cardiovascular and other systems were examined in detail during and after exposure. The results gave evidence that the crewmembers well adapted to the long-term flight effects. Their good health condition and high work capacity were supported by adequate medical procedures. Postflight readaptation developed similarly to what was seen after previous flights of shorter duration (6-11 months). No qualitatively new changes in the physiological systems were detected during or after this mission.

In 1987, the USSR cosmonauts Y. V. Romanenko (326 days), A. I. Laveikin (approximately 176 days), and A. P. Alexandrov (approximately 160 days) made a space mission on Mir. (A. I. Laveikin showed specific cardiovascular responses to exercise tests and was therefore replaced with A. P. Alexandrov). The most important medical result of this mission was that Yu. V. Romanenko, who remained in orbit for 3 months longer than anyone before, working intensively, did not exhibit any changes that were qualitatively different from those observed in previous long-duration space flights. The health status and work performance of other crewmembers were also good, although each of them showed individual responses. The postflight recovery period went smooth.

The influence of space flight factors on optomotor reactions and optokinetic resistance of 17 cosmonauts after prolonged (75 and 185 days) and short-term (4, 7, 14 days) flights is discussed.

A summary of the incidence of Space Motion Sickness (SMS) in 27 Soviet cosmonauts who flew on missions varying from 2-185 d in the Salyut-6/Soyuz vehicle complex is presented. A questionnaire indicated that 88% (24) of the cosmonauts developed some type of "illusionary sensations" while 44% (12) presented some degree of SMS. The SMS countermeasures used in flight included an antihistaminic drug, pneumatic cuffs applied to the thigh region, application of lower body negative pressure, a head cap that restricted head movement while simultaneously providing force stimulus to the cervical antigravity muscles, and finally the use of an insole counterpressure device that added pressure to the sole of the foot.