Changes of cardiac function during 60-day head-down tilt bed rest and effects of vibration exercise and Chinese medicine as countermeasures

AIM: To observe and compare the effects of vibration exercise and Chinese medicine on cardiac function during 60 d head-down tilt (HDT) bed rest. METHODS: Twenty one healthy, male subjects were randomly divided into control, vibration and Chinese medicinegroups (seven subjects in each group). All subjects were exposed to -6° HDT for 60 d. Control group received placebo, vibration group received vibration training and the Chinese medicine group received taikong yangxin pill. Cardiac systolic and pump functions were measured before HDT (supine) and on days 30 and 60 of HDT. RESULTS: In the control group, stroke volume (SV) and cardiac output (CO) decreased significantly on day 30 of HDT (P<0.05) and further decreased on day 60 of HDT (P<0.05), whereas total peripheral resistance (TPR) increased significantly on day 60 of HDT (P<0.05). In the vibration group, SV and CO decreased significantly on day 60 of HDT (P<0.05) and TPR increased significantly on day 60 of HDT (P<0.05). In the Chinese medicine group, no significant changes were observed during HDT. In all groups, pre-ejection period/left ventricular ejection time (PEP/LVET) and isovolumetric contraction time/left ventricular ejection time (ICT/LVET) increased significantly on day 60 of HDT (P<0.05). On day 60 of HDT, PEP/LVET and ICT/LVET decreased significantly in the Chinese medicine group compared with the control group and vibration group (P<0.05). CONCLUSION: HDT during a 60 d period may induce a reduction of the cardiac pump and systolic function. Chinese medicine significantly improves the cardiac pump and systolic function during bedrest, whereas the effect achieved by vibration exercise is less significant than by Chinese medicine.