Passive exercise failed to reverse OVX-induced bone microstructural degeneration to the extent achieved by HRT

Postmenopausal osteoporosis, characterized by estrogen deficiency-induced bone loss and elevated fracture risk, is commonly managed with hormone replacement therapy (HRT). This study aimed to evaluate whether passive exercise via whole-body vibration training (WBVT) could serve as an effective alternative to HRT (represented by 17β-estradiol (E2) supplementation) for improving bone microarchitecture and metabolism and to investigate whether combining WBVT with E2 supplementation yields superior bone-protective effects compared to E2 supplementation alone. To this end, mice underwent ovariectomy (OVX) or sham surgery. After a 4-week recovery, OVX mice received E2 supplementation, WBVT, combined treatment (E2 + WBVT), or no treatment for 10 weeks. Assessments included serum E2 levels, femur weight, femoral microarchitecture, tibial biomechanical properties, and the expression of osteogenic and osteoclastic factors. Compared to sham-operated mice, OVX mice exhibited lower serum E2 and femur weight, degenerative bone microarchitecture, impaired biomechanical performance, decreased osteogenic factors, and elevated osteoclastic factors - all notably reversed by E2 supplementation. The 10-week WBVT regimen partially improved bone microarchitecture, biomechanical performance, and homeostasis but was less effective than E2 supplementation. Moreover, the combination of E2 supplementation and WBVT did not demonstrate further improvements in these bone parameters relative to E2 supplementation monotherapy. In conclusion, the 10-week WBVT regimen did not produce bone improvements comparable to E2 supplementation in OVX mice, and the combined treatment did not enhance efficacy beyond that of E2 supplementation alone.