Simple Summary
Postmenopausal women face a high risk of osteoporosis, and the resulting chronic pain, fractures, and limited mobility impose a heavy burden on patients and society. While resistance exercise benefits bone health, it remains unclear whether long-term regular exercise can promote the healing of bone injuries caused by osteoporosis and how it works. This study tested the effects of 10-week weight-bearing ladder climbing in rat models simulating postmenopausal osteoporosis. The results showed that the exercise enhanced muscle strength, balanced hormones related to bone health, and reduced body weight in the osteoporotic rats. It also increased bone density and improved bone structure and strength—importantly, these benefits still existed 21 days after stopping exercise. Furthermore, in bone injury tests conducted after exercise cessation, rats that had undergone prior exercise showed significantly accelerated bone healing. This exercise exerts its effects by lowering a protein that inhibits muscle growth and regulating biological mechanisms that protect bones and muscles, with these effects remaining evident 21 days post-exercise. This study confirms that weight-bearing ladder climbing is a safe, drug-free way to alleviate postmenopausal bone loss, strengthen bones, and aid bone injury healing, providing important support for using exercise as a clinical intervention.
Abstract
Osteoporosis is highly prevalent in postmenopausal women, causing chronic pain, fractures, and limited mobility that burden individuals and society. While resistance exercise benefits bone health, its role in osteoporotic bone injury healing and underlying mechanisms remain unclear. This study aimed to explore the effects of 10-week weight-bearing ladder climbing exercise on ovariectomy (OVX)-induced osteoporosis and subsequent bone injury healing, and to investigate whether these effects are associated with the myostatin (MSTN) and Wnt/β-catenin pathways. Fifty-four 12-week-old female SD rats were randomized into Sham, OVX, and OVX + EX groups. Rats in the OVX and OVX + EX groups underwent ovariectomy to induce postmenopausal osteoporosis, and those in the OVX + EX group received 10-week weight-bearing ladder climbing. After the exercise intervention, 6 rats in each group were sacrificed; the remaining rats underwent femoral midshaft drilling to establish bone injury. The improvement in osteoporosis was evaluated via Micro-CT, biomechanical tests, RT-qPCR for mRNA detection, and Western blot for measuring protein levels of MSTN and Wnt/β-catenin pathway-related molecules at post-exercise and 21 days post-injury. Bone healing was reflected by the bone volume fraction at the bone injury site detected via Micro-CT at 10 and 21 days post-injury. This exercise significantly enhanced muscle strength and improved femoral bone mineral density (BMD), trabecular microstructure, and biomechanical properties in OVX rats. Meanwhile, the level of MSTN in the OVX + EX group was decreased, the expression of its downstream signaling pathways was inhibited, and the mRNA and protein expressions of Wnt/β-catenin were upregulated. Moreover, 21 days after exercise intervention, the biomechanical properties and bone microstructure of the OVX + EX group were still significantly superior to those of the OVX group, and the aforementioned molecular regulatory effect remained. In addition, pre-conducted exercise was able to promote increases in bone volume fraction at the bone injury site 10 and 21 days after drilling, which was conducive to bone injury healing. Ten-week weight-bearing ladder climbing ameliorates OVX-induced bone loss and promotes osteoporotic bone repair via regulating the MSTN/ActRIIB/Smad3 and Wnt/β-catenin pathways, providing evidence for exercise as a safe non-pharmacological intervention.