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  • Title: [Changes of cardiac function during 21 d head-down tilt bed rest and the effect of lower body negative pressure in the last week].
    Author: Sun XQ, Yao YJ, Wu XY, Hao WY, Jiang SZ, Qiao ZL.
    Journal: Space Med Med Eng (Beijing); 2001 Feb; 14(1):22-6. PubMed ID: 11710391.
    Abstract:
    OBJECTIVE: To investigate the change of cardiac function during 21 d head-down tilt (HDT) bed rest and the effect of lower body negative pressure (LBNP) in the last week in human. METHOD: 12 healthy male served as subjects which were randomly divided into control and LBNP groups, with 6 in each group. All of them were exposed to -6 degrees HDT for 21 d. The LBNP group received -4.0 kPa LBNP training 1 h/d in the last week of the test. The cardiac pump function and cardiac systole function were measured before, during and after HDT. RESULT: Cardiac output, cardiac index and stroke volume decreased significantly, whereas total peripheral resistance, pre-ejection period (PEP), isovolumetric contraction time/left ventricular ejection time (LVET) and PEP/LVET increased significantly during HDT in both control and LBNP groups, compared to pre-HDT values, and they returned to normal level on day 2 post HDT. PEP and PEP/LVET in LBNP group were significantly higher than those in control group on day 21 of HDT and day 2 post HDT. CONCLUSION: The reduction of cardiac pump function and cardiac systole function induced by 21 d HDT could not be prevented by LBNP training in the last week of 21 d HDT.
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