Muscle-bone interactions across age in men

This study examined the relationship of muscular strength and lean tissue with age-related patterns in bone mineral density (BMD) in men 20-81 years of age. Subjects were assigned to one of three age groups, Young Men (YM), ( n = 25, 20-39 yrs), Middle-aged Men (MM) (n = 24, 40-59 yrs), and Older Men ( OM) ( n = 23, 60-81 yrs). Isotonic and isokinetic strength was assessed for the quadriceps and hamstrings muscle groups. DXA ( Lunar DPX-IQ) was used to measure spine, hip, and total body BMD and body composition. OM had significantly lower ( p < 0.05) total lean body mass (LBM) than MM and lower leg lean mass (LM) than YM and MM. OM had significantly lower ( p < 0.01) BMD than YM and MM at the femoral neck and total hip sites and a higher proportion of OM were osteopenic and osteoporotic at the total hip site. Isotonic and isokinetic strength for both muscle groups was positively related ( p < 0.05) with the hip BMD sites ( r = 0.38-. 67). Leg LM also was positively related to hip BMD ( r = 0.37-. 58). Multiple Regression analyses determined that age and lean mass ( LBM or leg LM) were significant predictors ( p < 0.05) of femoral neck, and total hip BMD, while lean mass ( LBM or leg LM) was a significant predictor ( p < 0.05) of BMD at the spine and trochanter sites. Isotonic and isokinetic leg strength variables were significant predictors ( p < 0.05) of the total body, total hip and trochanter BMD. In conclusion, leg strength, leg LM, and total LBM were significant predictors of BMD in men, independent of age. These findings emphasize the importance of maintaining lean body mass for the bone health of aging men.