RELATION OF ISOMETRIC STRENGTH TO BONE MINERAL DENSITY IN MIDDLE-AGED MEN: THE DNASCO-STUDY 577

Osteoporosis is a growing public health problem not only in women but also in ageing men. We analyzed the relation of isometric strength (IS) of the upper and lower extremeties with bone mineral density (BMD) in 140 men, aged 53 to 62 years. The data were derived from the baseline measurements of the 3-year DNASCO exercise intervention trial. IS of the arm and leg flexor and extensor muscles was measured using a computerized measurement system (HUR Ltd, Finland). BMD in lumbar spine (L2-4), femoral neck, triangle of Ward and trochanter was measured using dual energy X-ray absorptiometry. IS of the arm flexors and extensors correlated positively with BMD in L2-4 (r=0.31 and 0.38, p<0.001), in triangle of Ward (r=0.29 and 0.30, p<0.001) and in femoral neck (r=0.24, p=0.006 and 0.30, p<0.001). IS of the leg flexors and extensors correlated with BMD to a lesser extent, coefficients varying from 0.18, p=0.033 (femoral neck) to 0.23, p=0.007 (L2-4). Body weight (BW) correlated positively with BMD at all sites (r=0.24 to 0.38, p=0.004 to<0.001), and dietary calcium intake (adjusted for energy intake, mg/MJ) correlated positively with BMD at trochanter (r=0.35, p<0.001) and at femoral neck (r=0.25, p=0.003) levels. In multiple stepwise regression analysis, BW, IS of the arm extensors and calcium intake explained 16.2% and 23.5% of the variance in trochanter and femoral neck BMD, respectively. Arm extensors IS, BW and age were the strongest determinants of L2-4 BMD explaining 20.3% of the variance. The presence of absence of cardiovascular diagnosis or smoking were not associated with BMD. These data suggest that muscular strength is an important determinant of bone mineral density in middle-aged men. Moreover, isometric strength of the arm muscles, which is relatively easy to measure, seems to offer a good estimate of overall muscular strength.