Physical Activity Levels and Bone Density Preservation in Postmenopausal Women
Bibliographic record
Abstract
Postmenopausal bone loss represents a significant public health concern, with approximately one in three women over age 50 experiencing osteoporotic fractures that compromise mobility, independence, and quality of life. While physical activity has been proposed as a modifiable factor influencing bone health, the relationship between habitual activity levels and bone density preservation in postmenopausal women requires further characterization. This research examined associations between objectively measured physical activity and bone mineral density at multiple skeletal sites in postmenopausal women, with longitudinal follow-up to assess two-year changes in bone status. We conducted a prospective cohort investigation at two Canadian academic medical centers between April 2015 and September 2018, enrolling 312 postmenopausal women aged 50 to 75 years without prior osteoporosis treatment. Physical activity was quantified using waist-worn accelerometry over seven-day monitoring periods, with participants categorized into sedentary, low active, moderately active, and highly active groups based on accumulated moderate-to-vigorous activity minutes. Bone mineral density was measured by dual-energy X-ray absorptiometry at lumbar spine, femoral neck, total hip, and distal radius sites at baseline and two-year follow-up. Results demonstrated significant positive associations between physical activity level and bone mineral density across all measured sites at baseline. Highly active women showed lumbar spine bone density of 0.97 g/cm² compared to 0.78 g/cm² in sedentary counterparts, representing a 24.4% difference (p < 0.001). Similar patterns emerged at femoral neck (23.5% difference), total hip (19.5%), and distal radius (21.4%) sites. Longitudinal analysis revealed divergent trajectories, with sedentary women losing 7.7% of lumbar spine bone density over two years while highly active women gained 1.0% (p < 0.001 for interaction). The correlation between weekly activity minutes and bone density was moderate to strong (r = 0.58 for lumbar spine, p < 0.001). Multiple regression analysis identified physical activity as the strongest modifiable predictor of bone density after controlling for age, body mass index, calcium intake, and years since menopause. These findings support physical activity as an effective strategy for bone density preservation in postmenopausal women, with dose-response relationships suggesting that higher activity levels confer greater skeletal benefits. Integration of activity promotion into postmenopausal health management could potentially reduce osteoporosis burden and associated fracture risk.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".