Effects of an 18-day flight on the human body

During their flight on board the Soyuz 9 A.G. Nikolayev and V.I. Sevastyanov adapted to weightlessness by the 3rd-4th day and stabilized their physiological functions by the end of the mission. During flight both cosmonauts maintained normal performance, sleep and appetite; they readily developed a new stereotype of movements and exhibited no noticeable increase of the circulatory function in response to a standard physical load. In contrast to the effects of shorter term flights, this mission "used unusual and distressing feelings in the crew members aggravated by distinct changes in the major- physiological systems during the first day of recovery. In the immediate postflight hours the transition from the recumbent to the sitting position brought about circulation disorders; 24 hours later the cosmonauts still walked with uncertainty and kept the erect position at rest on account of a significant elevation of their centre of gravity. Weight losses, shifts of water and mineral metabolism, bone tissue demineralization and symptoms of orthostatic intolerance observed in this flight were similar to those resulting from earlier short-term missions. Of importance was a dysbacteriotic change in the skin and nasal microflora. Physiological changes in the Soyuz 9 crew members were functional and reversible, being on the whole in agreement with predicted effects. These results call for the development of specific measures facilitating the post-flight adaptation of space pilots in view of future long duration space flights.