Is it true that exercise boosts stem cells? You have stem cells throughout your body which act as the “maintenance men” of the body (see our practice’s e-book-Orthopedics 2.0). The body’s mesenchymal stem cells that live in your bone marrow are most likely to become fat or bone, depending on which path they follow. Using treadmill-conditioned mice, a research team recently demonstrated that aerobic exercise triggers those cells to become bone more often than fat. The exercising mice ran less than an hour, three times a week, enough time to have a significant impact on their blood production. In sedentary mice, the same stem cells were more likely to become fat, impairing blood production in the marrow cavities of bones. This mechanism is the same one thought to lead to osteoporosis-stem cells in the bone preferentially become fat versus new bone. The same thing also likely occurs in bone diseases such as avascular necrosis. The upshot? To enhance the success of bone marrow derived therapies, aerobic exercise may help!