Muscle strength as a predictor of bone mineral density in young women

Abstract

It is widely accepted that physical activity is beneficial to bone. However, the specific relationships of muscle strength to bone mineral density (BMD) are poorly understood. We examined strength and BMD in 59 women aged 18-31 years who ranged in exercise patterns from sedentary to active. Mineral density of the right proximal femur (hip) and spine (L2-4) was evaluated by dual-energy x-ray absorptiometry. BMD at the midradius was measured by single-photon absorptiometry. Dynamic strength (one repetition maximum) was measured for the following muscle groups: back, elbow flexors (biceps), leg extensors (quadriceps), and the hip flexors, extensors, adductors, and abductors. Isometric grip strength was assessed by dynamometry. Mineral density at the hip correlated independently with muscle strength and body weight, but not with age. Specifically, femoral neck BMD was significantly correlated with back strength and weight, whereas trochanter and overall hip mineral density were significantly related to biceps, back, and hip adductor strength. Hip mineral density was not related to strength of the quadriceps groups or to that of the hip flexors, extensors, or abductors. In addition, muscle strength was an independent predictor of lumbar spine and midradius mineral density. In stepwise multiple regression analysis, biceps strength proved the most robust predictor of hip BMD and grip strength best predicted bone density at the lumbar spine and radius. We conclude that muscle strength is an independent predictor of bone mineral density, accounting for 15-20% of the total variance in bone density of young women.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle strength and bone in healthy women: effect of age and gonadal status

“…17 Our results further support the hypothesis of a site-specific effect of muscle strength: forces arising from muscular loading and contraction not only influenced BMD but also bone quality and microarchitecture, at least in postmenopausal women. 14,17,[29][30][31][32] Quantitative ultrasound is a validated technique in acquiring information about qualitative and structural features of bone and in identifying individuals at risk for fractures. 20 To our knowledge, this is the first study evaluating the relationship between handgrip strength and qualitative features of bone, both assessed at the upper dominant limb.…”

Muscle Mass Is More Strongly Related to Hip Bone Mineral Density Than Is Quadriceps Strength or Lower Activity Level in Adults Over Age 50Year

“…In contrast, studies of adults under age 42 have suggested that physical activity is a better predictor of BMD than is knee extensor strength. (20)(21)(22) Similarly, studies of younger athletic men have revealed that, although knee extensor strength is associated with BMD at the hip, activity level predicts this relationship better than either knee extensor strength or lean body mass (LBM). (23) Alternatively, differences between our results and those of prior studies may stem from measurements used.…”

Motor assessment using the NIH Toolbox

“…21 For example, knee extensor muscles have been identified as representative of lower-extremity strength because of their central role in key functional tasks, such as walking, standing from a chair, and climbing stairs. [22][23][24] Muscle strength of the limbs and trunk declines with age and is associated with an increased risk of falls, 25 hip fractures, 26 loss of bone mineral density, [27][28][29][30] and long-term survival in severe congestive heart failure, 31 functional dependence in people aged 75 years, 32 and loss of functional status in hospitalized patients. 33 Balance allows humans to be able to orient the body in space, maintain an upright posture under static and dynamic conditions, and move without falling.…”