Measured Aerobic Fitness and Bone Density in 237 Middle-aged Women

Purpose The main objective of the present study was to determine the extent to which objectively measured aerobic fitness (VO2mSX) was predictive of bone mineral density (BMD) in 237 middle-aged women. Additional aims were to determine the extent to which differences 3n age, body weight, and objectively measured physical activity affected the relationship between and BMD.

Methods subjects were primarily Caucasian, educated, and married. Only nonsmokers and women who had SMIs <30 were used as subjects API subjects were 35-45 yrs old (mean age: 40 yrs). VO2max was measured using gas analysis during a graded exercise test to exhaustion on a motorized treadmill Physical activity (ACT) was measured objectively using CSA accelerometers, worn continuously for 7 consecutive days. All 1008 activity counts across the week of monitoring were summed to index total physical activity. Bone density was measured at four sites using a calibrated Hologic 4500W dual energy x-ray absorptiometry (DXA) machine: total body (minus head), left hip, legs, and total spine.

Results With body weight controlled, VO2m2X was strongly related to bone density at the hip (F = 342, p = 0.0344), legs (F = 15.28, p = 0.000 1), and total body (F 6 32, p = 0 0021). Bone density of the spine was not related significantly to VO2max with body weight controlled (F = 1. 17, p = 0.3110). After adjusting for differences in ACT, the relationships between and BMD were weakened substantially.

Conclusion Evidently, level of aerobic fitness is closely associated with bone density because aerobic fitness is strongly related to physical activity levels. In short, the strong relation between aerobic fitness level and BMD is largely dependent on differences in physical activity among middle-aged women.