Exercise and the Prevention of Osteoporosis

Osteopenia, a condition of diminished bone mass, becomes osteoporosis when mechanical demands exceed the ability of the skeletal structure to support them. Mechanical signals generated by exercise can mitigate bone loss as well as help preserve the musculoskeletal "system." The physical and/or biologic basis of how mechanical signals are transformed into anabolic agents for bone and other tissues is called mechanotransduction and may represent the foundation for a nondrug approach to treat osteoporosis. The sensitivity of bone cells to mechanical signals, including stromal cells, osteoblasts, and osteocytes has been well documented, but it is difficult to designate a critically responsive cell. The role of mesenchymal stem cells (MSCs) in regulating the adaptive response to mechanical signals is also being investigated, with the demonstration that exercise can bias MSCs toward osteoblastogenesis, while disuse increases adipogenesis within the bone marrow.