Site-Specificity of Bone Mineral Density and Muscle Strength in Women

Abstract

We proposed that there are significant correlations between muscle strength and bone mineral density in premenopausal women and that these correlations are site-specific. To test this hypothesis, we examined the relationships among site-specific bone mineral density, physical activity, and muscle strength in a group of 96 healthy premenopausal Caucasian women. Bone mineral density was measured at the lumbar spine and at three sites in the proximal femur (trochanter, femoral neck, and Ward's triangle) with dual-energy x-ray absorptiometry and at the mid-radius with single-photon absorptiometry. The muscle strength of hip and spinal muscle groups was determined with a strain gauge isodynamometer, and grip strength was measured with the JAMAR dynamometer. The strength of shoulder girdle muscle groups was evaluated with the use of free weights. Physical activity was determined by surveying the subjects and by using a standardized scale. Data analysis revealed significant linear correlations of muscle strength with bone mineral density at the mid-radius (r = 0.31; P = 0.002) and at the hip (r = 0.26; P = 0.01). Grip strength was significantly correlated with bone mineral density of both the spine and the femur (r = 0.24, r = 0.34; P < 0.05 for both). Back extensor strength correlated with bone mineral density of the hip (Ward's triangle; r = 0.23; P = 0.023). However, there was no significant positive correlation between the strength of the spinal flexor or extensor muscles and the site-related bone mass (lumbar spine). Only one of the three components of the physical activity score (job) positively correlated with vertebral bone mineral density (r = 0.21; P = 0.04). Physical activity negatively correlated with age (r = 0.24; P = 0.02). We conclude that in premenopausal women, the effect of muscle strength on bone mass is more systemic than site-specific. A positive correlation between vertebral bone mass and components of physical activity demonstrates that even job-related physical activity is an important factor in maintaining adequate bone mass.

Handgrip Strength is an Independent Predictor of Distal Radius Bone Mineral Density in Postmenopausal Women

“…Moreover in some studies the correlation has been shown at some sites but not at other sites [3,5,12,20,21]. Con¯icting data have also been reported about the relation between bone density sites and the strength of muscles not attached to those bones [3,5,7,8,12,16], and recently it has been suggested that the effect of muscle strength on bone mass is more systemic than site speci®c [20].…”

Association between moderate physical activity, spinal motion and back muscle strength in postmenopausal women with and without osteoporosis

“…However, the changes in the osteoporotic spine may be more related to pathology in the spinal soft tissues, especially back muscle weakness [12,13,44]. Some authors [7,14,16,17,29,44,45] recommended back extensor strengthening exercises as a way to control the pain and disability that are part of this disease condition.…”

“…The BMD (g/cm 2 ) of the lumbar spine and the non-dominante hip were measured in each subject with dual-energy X-ray absorptiometry (DEXA) using a Lunar DPX instrument (General Electric Medical Systems, USA) [12,21,26] by a trained technician. In strict accordance with medical guidelines [27], individuals of 65 years of age or older are evaluated mainly at the hip and the measurement of the spine is used for comparison and confirmation of the diagnosis.…”

“…Several studies have provided evidence that increased physical activity may be associated with a lower rate of bone loss [9][10][11], but physical activity has a greater effect on muscle strength than BMD [12].…”

Physical Activity and Risk Factors for Hip Fractures in Thai Women

“…Subsequent reports were consistent with their conclusion. In premenopausal women job-related physical activity is an important factor in maintaining adequate bone mass [5]. Another study by Madsen et al [6] revealed that weight-bearing exercise enhanced bone mineral density (BMD) in young adult women.…”