The Relationship Between Usual Daily Physical Activity With Serum Markers Related to Bone Metabolism and Demographic Characteristics in Postmenopausal Women Aged 50-65 Years

Background: Bone turnover markers can predict subsequent changes in bone status. This study aimed to investigate the relationship between usual daily physical activity (PA) with bone markers. Methods: This cross-sectional study was conducted on 500 postmenopausal women aged 50-65 years in Tabriz-Iran in 2018. The women were recruited by a simple random method. The International Physical Activity Questionnaire was used to assess PA. The laboratory tests of 25-Hydroxyvitamin D3, alkaline phosphatase, calcium, and phosphorus were also used to examine bone function. Results: The education, income, employment status, sun exposure, and history of exercise were significantly correlated with PA. Among reproductive characteristics, only menopausal age showed a significant relationship with total PA levels (r = .285, P=.048). None of the anthropometric indices showed a statistically significant relationship with total PA. Serum calcium (r = -.242) and phosphorus (r = -.045) levels showed negative and inverse relationships with total PA. The intensity of this association was statistically significant only for the calcium (beta = -0.108, 95% confidence interval, -0.117 to 0.098; P=.023). 25-Hydroxyvitamin D3 (r = .007) and alkaline phosphatase (r=.046) were directly and positively but nonsignificantly correlated to the intensity of total PA. Conclusion: Usual daily physical activity with any levels has no effect on bone markers except for calcium. Despite of the beneficial effects of PA, our findings showed that usual daily physical activity without increasing total PA cannot affect bone health. For maximal effects of PA on bone health, it seems that a degree of intensity, continuity, and regularity of PA programs should be considered to stimulate bone formation.