Abstract / Summary
Background: This cross-sectional study investigated the associations of bone-specific physical activity (PA), assessed using the Bone-Specific Physical Activity Questionnaire (BPAQ), with bone mineral density (BMD) and arterial stiffness in premenopausal women. Methods: A total of 270 premenopausal women participated. Continuous total BPAQ (tBPAQ) was analyzed as the primary exposure in the revised analyses, while tertile-based analyses were retained as secondary analyses. BMD was measured by dual-energy X-ray absorptiometry, and arterial stiffness was assessed using brachial-ankle pulse wave velocity (baPWV). BMD models were adjusted for age, fat-free mass (FFM), and BMI, and the mean bilateral baPWV model was adjusted for age, mean arterial pressure, and BMI. Results: Higher tBPAQ was positively associated with whole-body, femoral neck, total femur, and lumbar spine BMD after false-discovery-rate correction (all q < 0.001). The forearm association was weaker (B = 0.0040 g/cm2 per 10 tBPAQ points; q = 0.019) and was not retained in the log1p-transformed sensitivity analysis (p = 0.162) or the adjusted tertile comparison (p = 0.062). There was no evidence of an adjusted linear association between tBPAQ and mean bilateral baPWV (B = 5.1 cm/s per 10 points; 95% CI, −4.6 to 14.7; p = 0.301; q = 0.301). Exploratory quadratic models suggested possible nonlinearity for femoral neck BMD and mean bilateral baPWV, but these findings were hypothesis-generating. Conclusions: Higher cumulative bone-specific PA was associated with higher BMD, particularly at weight-bearing skeletal sites, whereas the forearm finding was less consistent across analyses. No adjusted linear association with arterial stiffness was identified. Longitudinal and interventional studies are needed to clarify temporality and possible nonlinear relationships.