Influence of grip strength on metacarpal bone mineral density in postmenopausal Japanese women: a cross-sectional study.

Most published studies on the role of muscle strength in the maintenance of bone mineral density (BMD) focused on the relationship between specific muscle groups and adjacent bones, mostly in young and premenopausal women. This study examined the influence of grip strength on BMD of the metacarpal index in postmenopausal Japanese women. Subjects included 1168 postmenopausal women aged 40-70 years. BMD measurement was done with computed X-ray densitometry (CXD) by analyzing X-ray films of the right second metacarpal index. Grip strength was measured in both the dominant and nondominant hands using a squeeze dynamometer. Grip strength (r = 0.2474; P = 0.0001) and age (r = -0.5443; P = 0.0001) significantly correlated positively and negatively, respectively, with BMD. Physical activity (r = 0.1318; P = 0.0001) also correlated positively with BMD. Breastfeeding (r = -0.1658; P = 0.0001), however, correlated negatively with BMD. Subjects with a history of regular physical activity had higher grip strengths and BMD, than those with no physical activity. Adjustment for age, physical activity, calcium intake, BMI, breastfeeding, testing site, and menopausal type indicated a significant (P for trend = 0.0013) positive association of grip strength with BMD. Subjects with stronger grip strengths had a decreased risk for low BMD.