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This paper presents medical results obtained in a Salyut-7 8-month manned mission in which a physician-cosmonaut took part. The results include body mass and height measurements, vestibular studies, cardiovascular studies at rest and in response to staged functional loads (with echocardiographic examinations accentuated), metabolic and hormonal studies. The paper also gives information about medical aspects of extravehicular activities. It is emphasized that during the mission both old and new methods of research were used and medical results of preceding flights were considered.

Before and after 24-hour water immersion test subjects performed a submaximal workload on a bicycle ergometer. Changes in their hematocrit, circulating plasma volume and fluid balance were compared with those during immersion. As a result, the test subjects were subdivided into two groups. For one group the workload was very hard; adaptation to immersion was accompanied by significant renal losses of fluid from the intra- and extravascular space. The bicycle ergometry test after immersion demonstrated a decrease of exercise tolerance combined with circulatory disorders. The other group showed a higher exercise tolerance; after immersion exercise tolerance remained high at the expense of the reserves that maintained optimal blood supply to the working muscles.

The cardiovascular function of four test subjects exposed to 28-day "dry" immersion was examined before and after 6-day cycles of rotation in a short-arm centrifuge to provide 1-2 Gz, bicycle ergometer exercise, and their combination. An exposure to acceleration of 3 Gz in a 7.25 m arm centrifuge was used as a provocative test. The above countermeasures reduced but not eliminated entirely immersion-induced cardiovascular deconditioning. From this study a combined use of acceleration of 1-2 Gz in a short-arm centrifuge and bicycle ergometer exercise can be recommended as a countermeasure against cardiovascular deconditioning in weightlessness.

The effect of intermittent immersion on orthostatic tolerance, fluid-electrolyte metabolism and neuromuscular system was investigated. Control and experimental immersions were used. Experimental immersion was preceded by 12-hour exposure to immersion at night for three times. Experimental immersion was accompanied by reduced renal excretion of fluid, sodium and potassium and normalization of the muscle tone. After experimental immersion orthostatic tolerance approached the control level. The difference in the physiological effects of control and experimental immersions seem to be associated with the capacity of the human body to adapt to immersion, if it is applied intermittently.

Healthy male test subjects, aged 20 to 45, were exposed to acceleration of +6 Gx for 1200 sec and of +10 Gx for 60 sec. Three gradients of the centrifuge acceleration were used in the latter case. In every experimental run the test subjects were exposed to accelerations while breathing air or a helium-oxygen atmosphere. The positive effect of the helium-oxygen atmosphere was seen in an increase of the respiration intensity and in an elevation of pulmonary ventilation and gas exchange. This may be associated with a decline of the aerodynamic resistance to breathing. The positive effect of the helium-oxygen atmosphere was more pronounced during accelerations of +4 to 8 Gx and depended on the total exposure time.

It was demonstrated that renal excretion of fluid, osmotically active substances and electrolytes could be reduced, using low gravitational exposures (+GZ). The degree and duration of water and electrolyte retention were different with respect to the experimental time. The major physiological mechanisms of the changes in fluid-electrolyte metabolism were: a decrease in the glomerular filtration rate and a change in water and ion transport in renal tubules.

As a result of 370 experiments in a 2 m-arm centrifuge, high human tolerance to acceleration of +0.8, 1.2 and 1.6 Gz (at the level of feet) was demonstrated. Cardiovascular reactions depended on the value, duration and frequency of acceleration exposures. Cardiovascular responses included, primarily, changes in regional circulation of the legs.

The frequency and pattern of cardiac arrhythmias were studied during an exposure to acceleration +3 Gz for 5 min before and after 3- and 13-day dry immersion. Following immersion the frequency of extrasystolic arrhythmias increased four-fold and more severe arrhythmias--group and systemic extrasystoles--developed as compared with control exposures. The following factors--increased in the parasympathetic tone, disorders in the systemic and regional circulation and fluid-electrolyte balance--seemed to be mainly responsible for distrubed regulation of the cardiovasucular rhythm during a post-immersion exposure to acceleration.

Test subjects were exposed to 13-day water immersion per se or combined with centrifugation. The immersion did not influence the state of ventilation and gas exchange at rest, diminished significantly the functional capabilities of external respiration. An exposure of the test subjects to acceleration during the second half of water immersion resulted in the normalization of the functional reserves of external respiration. This may be a consequence of an increase in the total physical tone of the body.

The activity of the sympathoadrenal system (SAS) of 12 volunteers exposed to water immersion for 7 days was studied. Before and after water immersion six of the test subjects were exposed to acceleration of +3 Gz for 15 min. It was demonstrated that water immersion increased the hormonal activity and decreased the transmitter activity of the SAS. Exposure to acceleration stimulated the SAS, thus increasing immersion tolerance.

Orthostatic tolerance after 7-day dry immersion and head-to-feet acceleration was investigated on test subjects with and without an antigravity suit of bladderless type. With the suit on, the 20 min tilt test at 70 degrees prior to immersion induced less marked changes than without the suit. When the suit was on, cardiovascular reactions to tilt tests after immersion and acceleration improved. The maximum heart rate decreased from 135 +/- 4 to 101 +/- 5 beats/min (p less than 0.01), minimum stroke volume increased from 29 +/- 2 to 41 +/- 3 ml (p less than 0.05), and pulse pressure grew. Thus, an antigravity suit may help increase initial orthostatic tolerance and maintain it after the combined effect of simulated hypogravity and acceleration.

Exposure to simulated weightlessness (7-day water immersion and 7-day head-down tilt) caused a decrease in the activity of malate (MDH) and isocitrate dehydrogenase (ICDH), and creatine phosphokinase dehydrogenase (ICDH), and creatine phosphokinase (CPK) at the expense of its MM isoform whereas the activity of alanine (ALT) and aspartate aminotransferase (AST) and pattern of distribution of MDH isoforms remained unchanged. Exposure to acceleration of +3 Gz before and after simulated weightlessness revealed similar changes in the activity of MDH, ICDH, ALT, AST and MDH cytoplasmic fractions. However, the higher increase in the enzyme activity after simulated weightlessness may give evidence for a greater change in cell membrane permeability during acceleration effects that followed simulated weightlessness.