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Results for “WEIGHTLESSNESS”

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At least 811 records · Page 45Linked to original sources
PubMedDate not supplied

[Comparative analysis of the effect of weightlessness and its model on the velocity-strength properties and tonus of human skeletal muscles].

The effect of various types of support elimination (actual zero-g, water immersion, and head-down tilt) on the strength-velocity properties and tone of leg muscles was investigated. With all the exposures used, there was a high correlation between the tone decrease and the strength potential of antigravitational muscles, as well as the degree of support elimination (immersion and bed rest). This suggests that the tonic changes associated with the decrease of the support input are the major factor responsible for motor disorders during short-term exposures to zero-g.

Action Potentials↗
PubMed1983

Cardiovascular adaptation to weightlessness.

Exposure to actual and simulated O g causes a significant central or cephalad shift of intravascular and interstitial fluid that triggers a complex set of cardiovascular and systemic adaptations. These adaptations are, in turn, directly responsible for the cardiovascular dysfunction that is apparent after return to normal gravity. However, critical information on several important adaptive mechanisms is incomplete or lacking. An attempt will be made to resolve these problems during a future dedicated Life Sciences Space Shuttle flight. A series of cardiovascular experiments will utilize direct measurements of central venous pressures, cross-sectional echocardiography, and noninvasive measurements of systemic and peripheral blood flow at rest and during stress. Autonomic control mechanisms will be studies in detail.

Adaptation, Physiological↗
PubMedDate not supplied

[Changes in several indicators of blood rheology in experiments simulating weightlessness].

Changes in blood rheological parameters of 21 male volunteers, aged 25-37 years, were studied. The test subjects were subdivided into three groups. Nine subjects of Group 1 were exposed to head-down tilting (-8 degrees) for 14 days, six subjects of Group 2 were exposed to 7-day continuous immersion, and six subjects of Group 3 to intermittent immersion. During head-down tilting the apparent viscosity and hematocrit and then caisson viscosity increased. By day 7 the coefficient of red blood cell aggregation decreased significantly. These changes persisted till the end of the tilt study. The above rheological parameters returned to normal three days after the exposure. During continuous immersion the apparent viscosity showed the largest changes. Other specific changes included a moderate decrease of hematocrit, lack of significant changes in the yield limit of blood and a tendency towards an increase in the erythrocyte aggregation coefficient. Three days after the exposure the blood viscosity was much higher than before the study. During intermittent immersion rheological changes were induced by the first 36-hour exposure when shifts in blood viscosity and other parameters were most significant. It should be noted that following this exposure 72 hours of normal motor activity did not result in the normalization of the above rheological parameters.

Adolescent↗
PubMed1983

Effect of weightlessness on the function of rat skeletal muscles on the biosatellite "Cosmos-1129".

Isometric tension of glycerinated fibrils of different skeletal muscles was studied in white rats carried in the biosatellite "Cosmos-1129" for 18.5 days. Expression and trends of the changes in contractile properties of muscle preparations depend on their functional specialization. The most sensitive reaction was displayed by the soleus muscle which consists predominantly of slow fibres.

Adaptation, Physiological↗
PubMed1983

[Effect of water immersion as a model of weightlessness on lung closing volume].

The effect of 7-day water immersion combined at night with head-down (6 degrees) tilting on the volumes of lung expiratory closing was examined in 6 healthy male test subjects, aged 25-35. During immersion they showed, along with a stable reduction of the lung vital and functional residual capacity (by 4.2 and 14.8%, respectively), an increase in the fraction parameters of the expiratory closing volumes. The increase in the closing volume (up to 40%) (P less than 0.05) was particularly distinct on immersion day 2. Subsequent changes indicated gradual recovery of the closing volumes and a decline in regional nonuniformity of lung ventilation. The time-course variations in the closing volumes may be attributed to an increase in the intrapulmonary blood volume at the early stage of adaptation to immersion and to a decrease in the nonuniformity of the ventilation-perfusion ratios.

Adult↗