The Importance of Bone Mineral Density in Women

Article excerpt

Osteoporosis is a serious bone disorder affecting over 25 million Americans, 80 percent of whom are women. Low bone mineral density is a major precursor to osteoporosis. Physical activity and calcium intake have been shown to cause significant gains in bone mineral density. The lack of importance placed on physical activity in school-age children can lead to a life of little physical activity, resulting in low bone mineral density and ultimately leading to fractures and dislocations.

Ford, Bass, Turner, Mauromoustakos and Graves (2004) studied 157 college-age females to determine the effect of past and present physical activity levels on bone mineral density. Subjects were selected from the age group of 18 to 39 in order to attempt to measure them close to their peak bone maturation. The American College of Sports Medicine guidelines for general fitness were used to classify each participant as being physically active. Although guidelines have not been established for the minimum requirements necessary to increase bone mineral density, moderate activity two or more times per week has been shown to increase bone health. Self-reported data were used to determine the level of past and present physical activity. Participants were asked questions such as "Did you participate in high school sports?" and "In the past month, how often did you walk a mile or more at a time without stopping; jog or run; ride a bicycle or an exercise bicycle; swim; do aerobics or aerobic dancing; do other dancing; do calisthenics or exercises; do gardening or yard work; lift weights; do other exercises, sports or physically active hobbies not mentioned?" Other variables included in the survey were information on heredity, nutritional information, milk consumption, contraceptive usage, and whether or not each participant was breastfed as an infant.

Dual-energy X-ray absorptiometry (DEXA) equipment was used to collect measurements of the subjects' bone mineral density and total body composition. To determine bone mineral density, measurements were made of the left femur and the anterior-posterior lumbar spine.

The results showed that 66 percent of the participants were active in high school sports and 81 percent were currently physically active more than 12 times per month. Lack of high school sports participation and lean tissue were significant risk factors for low lean femoral bone mineral density while lack of present physical activity and lean tissue were significant risk factors for low spinal bone mineral density. …