Dr. Taaffe et al., DYNAMIC MUSCLE STRENGTH AS A PREDICTOR OF BONE-MINERAL DENSITY IN ELDERLY WOMEN, Journal of Sports Medicine and Physical Fitness, 35(2), 1995, pp. 136-142
Although muscle strength has been shown to predict bone mineral densit
y (BMD) in older adults, the variance explained by isometric and isoki
netic testing has been generally low (<20 %) and limited to only a few
exercises and muscle groups. To elucidate the relationship of muscle
strength to BMD at multiple sites, and to ascertain the most robust pr
edictor of BMD using isotonic strength testing apparatus, we examined
dynamic muscle strength and BMD in 30 healthy elderly women aged 65-82
years. BMD of the spine (L(2-4)), proximal femur (neck, trochanter. W
ard's triangle), forearm (midradius), and whole body were measured by
dual-energy X-ray absorptiometry. Dynamic strength (1-RM), utilizing i
sotonic weight-lifting equipment, was assessed for 10 standard upper a
nd lower body exercises. In stepwise multiple regressions, leg press w
as the only independent predictor of spine (R(2)=0.11), neck and troch
anter (R(2)=0.21 and 0.18), forearm (R(2)=0.21), and whole body BMD (R
(2)=0.19), while bench press was an independent predictor of Ward's BM
D (R(2)=0.12). The most robust predictor of regional and whole body BM
D using isotonic equipment was the leg press, which may reflect overal
l skeletal health in this population. The portion of variance explaine
d by dynamic muscle strength (11-21%) is similar to that reported when
strength is assessed by isometric and isokinetic testing. The relatio
nship of dynamic strength to BMD was not generally site-specific.