Relationship Between Physical Activity Intensity And Bone Mineral Density In Premenopausal Women

Abstract

Osteoporosis has become a global health problem. Mechanical loading during physical activity (PA) and exercise increases and maintains bone mass and strength. Quantitative PA measures are needed to identify the functional loading intensity that is beneficial for bone health. PURPOSE: This study aimed to examine the relationship between PA intensity and bone mineral density (BMD) at the femur and spine in premenopausal women. METHODS: The data from 2005–2006 National Health and Nutrition Examination Survey (NHANES) were used for this study. PA was assessed using ActiGraph accelerometers, and bone health metrics were measured through dual-energy X-ray absorptiometry. After removing all missing values, 1446 female participants (Age: 47.61 ± 5.39 yr., Height: 162.01 ± 6.30 cm, Weight: 74.60 ±16.80 kg, BMI: 28.45 ± 6.30 kg/m2) remained. PA intensity is translated from accelerometer counts per minute (cnts/min) using the thresholds in previous calibration studies, e.g.: Light intensity activity = 100–1951 cnts/min, Moderate–vigorous intensity = 1952–5724 cnts/min, and Vigorous intensity > 5724 cnts/min. The bone health metrics were the BMD of femur neck, trochanter, total femur, and total spine. The correlations between PA intensity with bone health metrics were computed. RESULTS: The means and standard deviations of Light intensity = 537.79 ± 85.59 (cnts/min), Moderate-vigorous intensity = 2694.48 ± 340.54 (cnts/min), and Vigorous intensity = 7120.53 ± 1721.06 (cnts/min). A low correlation between overall PA intensity and total BMD (r = 0.01) was found. Correlations between different PA intensities and BMD are summarized below:CONCLUSION: Although low correlation was found between PA intensity and BMD, only no or low correlation was found between BMD and a specific PA intensity. Lack of variabilities within a specific PA intensity may be the reason. More studies are needed to understand the relationship between PA intensity and bone health.