Bone mineralization pattern refers to the types of minerals (calcium is of paramount importance) that are incorporated into bone, the amount of the minerals that are present (referred to as the bone density), and the possible differences in bone mineral composition and density in different regions of the skeleton.
Calcium, in the form of calcium phosphate, is incorporated into bone as a highly structured crystal called hydroxyapatite. This crystallized mineral is essential for the hardness of bones, and for their rigidity—the latter is important, otherwise the bones may inadvertently bend when a force is applied.
Hydroxyapatite makes up about one-quarter of the volume and approximately half the mass of normal adult bones. The calcium crystals tend to associate with fibrils of collagen in bones.
The importance of calcium is underscored in osteoporosis, which involves the progressive loss of calcium. Bones become more fragile and more prone to fracture and breakage under stresses that would otherwise not be damaging. Post-menopausal women are especially susceptible to osteoporosis. As well, female athletes who, as a result of training stress, cease menstruation (amenorrhea) can trigger premature osteoporosis, which may persist despite calcium supplementation.
In female athletes, exercise can also produce increased bone mineralization in regions that are especially stressed by the athletic activity. As one example, elite figure skaters and gymnasts can have increased bone mineral density in the bones in the lower body. In another example, physical activity in adolescence can increase the bone density of the femur (the portion of the thigh bone with the socket into which the hip joint fits).
A number of studies involving female athletes has established that the increased bone density that is a benefit of exercise outweighs the potential risk of bone loss due to osteoporotic loss of calcium.
Nutrition is important in maintaining bone mineralization patterns. For example, vitamin D is involved in calcium regulation, and a vitamin D deficiency can lead to the depletion of bone minerals. This is relevant to athletics, where the need to maintain a slim, lightweight body may tempt an athlete to adopt an improper diet.