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ARS Home » Pacific West Area » Davis, California » Western Human Nutrition Research Center » Obesity and Metabolism Research » Research » Publications at this Location » Publication #212529

Title: Quantifying Leisure Physical Activity and Its Relation to Bone Density and Strength

Author
item SHEDD, KRISTINE - UC DAVIS
item HANSON, KATHY - IOWA STATE UNIV.
item ALEKEL, D. - IOWA STATE UNIV.
item SCHIFERI, DANIEL - BONE DIAGNOSTOCS
item HANSON, LAURA - IOWA STATE UNIV.
item Van Loan, Marta

Submitted to: Medicine and Science in Sports and Exercise
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2007
Publication Date: 12/1/2007
Citation: Shedd, K.M., Hanson, K.B., Alekel, D.L., Schiferi, D.J., Hanson, L.N., Van Loan, M.D. Quantifying Leisure Physical Activity and Its Relation to Bone Density and Strength. Medicine and Science in Sports and Exercise. 2007. DOI: 10.1249/mss.0b013e318155a7fe 2189-2198.

Interpretive Summary: Both diet and physical activity are important to bone health and add to an increased bone density and a reduction in osteoporotic fracture risk. Osteoporotic fractures can also be reduced by improved micro-architecture of the bone. In animals, physical activity has been shown to improved bone density and the micro-architecture, however, data are more limited in humans. We explored the effect of leisure time physical activity on properties of bone density and strength in a group of early postmenopausal women. Leisure time physical activity was coded for properties such as bone loading impact, ground reaction forces, total activity score, peak strain, strength-strain index, and polar moment of inertia. We found that the strength-strain index and the total activity score were positively associated with higher levels of cortical thickness and cortical area in the femur. We also determined that more positive effects of physical activity on bone were observed when 4 or more hours per week was spent in leisure time physical activity or approximately 30 minutes per day.

Technical Abstract: Purpose: Compare three published methods of quantifying physical activity (total activity, peak strain, and bone loading exposure [BLE] scores) and identify their associations with areal bone mineral density (aBMD), volumetric BMD (vBMD), and bone strength. Methods: Postmenopausal women (N = 239; mean age: 53.8 y) from Iowa (ISU) and California (UCD)completed the Paffenbarger Physical Activity Questionnaire, which was scored with each method. Dual energy x-ray absorptiometry assessed aBMD at the spine, hip, and femoral neck, and peripheral quantitative computed tomography (pQCT) measured vBMD and bone strength properties at the distal tibia and midshaft femur. Results: UCD women had higher total activity scores and hours per week of leisure activity. All scoring methods were correlated with each other. No method was associated with aBMD. Peak strain score was negatively associated with polar moment of inertia and strength-strain index at the tibia and total activity score was positively associated with cortical area and thickness at the femur. Separating by geographic site, the peak strain and hip BLE scores were negatively associated with pQCT measures at the tibia and femur among ISU subjects. Among UCD women, no method was significantly associated with any tibia measure, but total activity score was positively associated with measures at the femur (p < 0.05 for all associations). Conclusion: Given the significantly greater hours per week of leisure activity done by UCD subjects, duration may be an important determinant of the effect physical activity has on bone. The positive association between leisure physical activity, assessed by the total activity score, and cortical bone measures in postmenopausal women may indicate a lifestyle factor that can help offset age-related bone loss.