Effects of whole body vibration on prevention of bone loss in 8-week tail-suspended male rats

Objective: To investigate the effects of low frequency whole body vibration on preventing the bone loss of rats' lower limbs induced by tail suspended. Method: 40 male rats were divided randomly into 4 groups, including tail suspended group(sus, n=10), tail suspended + ground stimulus group (s+g, ground stimulus: 30min/d, 5d/w, n=10), tail suspended + vibration group (s+v, vibration stimulus: 45Hz, 0.2-0.5g, 30min/d, 5d/w, n=10), and control group (con, n=10). Bone mineral density (BMD) of femur, trabecular structure in femur head, and the concentration of bone formation and resorption markers (Ca, P, ALP, BALP, PICP-1, TRACP ) in serum were tested after 8 weeks experiment. The tibias were taken to experiencing the 3-point bending test to explore the anti-load ability changes. Result: After 8 weeks tail suspended, the BMD of femur head (mainly trabecular bone) in s+v group were significantly higher than that in sus and s+g group, but lower than con group(P<0.05). But the BMD of middle femur (mainly cortical bone) had no great changes between groups. The trabecular structure parameter (BVF%, Tb.Th) in s+v group were also higher than sus and s+g group(P<0.05), and with no difference with con group(P>0.05). The max load and stiffness of tibia in con group were higher than that in sus, s+g and s+v group, but it had no statistical difference among the latter three groups (P>0.05). There were no changes of the concentration of bone formation and resorption markers in serum between groups. Conclusion: 45Hz whole body vibration could prevent the trabecular bone loss induced by tail suspended, but not the cortical bone. It seems that the benefit of whole body vibration to totally prevent the bone loss during long-duration space flight is limited.