DXA Appendicular Lean Soft Tissue Association with Skeletal Muscle Mass Function

Abstract

0481 An important component of assessing fitness in children and adolescents is quantifying skeletal muscle mass (SM) and function. One recently develop method of measuring SM is dual-energy x-ray absorptiometry (DXA), but reported methods were developed in adults. The DXA approach is based on the assumption that appendicular lean soft tissue (LST) as measured by DXA has a large fraction as SM. PURPOSE: In the present study we examined the associations between DXA-measured arm LST (kg), magnetic resonance imaging (MRI) arm SM (kg), and grip strength (kg) using a hand dynamometer. METHODS: Magnetic resonance imaging was carried out using 1 cm thick slices with 4 cm gaps. Adipose tissue-free SM was estimated by hand segmentation of each image slice. Subjects were ethnically-mixed healthy children and adolescents. The subjects were 47 males and females, ages 6 to 17 yrs. RESULTS: There was strong correlations between arm LST and corresponding MRI-measured arm SM [right arm, SM = 0.30xLST + 0.11, R2 = 0.93, p<0.001; left arm, SM = 0.56xLST – 0.063, R2 = 0.93, p<0.001]. There were also good and non-significantly different correlations between grip strength and DXA-LST [right arm, grip = 9.6xLST + 5.9, R2 = 0.73, p<0.001; left arm, grip = 9.2xLST +5.3, R2 = 0.69, p<0.001] and MRI-SM []. The findings did change when age and sex were entered into the analysis. CONCLUSION: Our findings thus indicate a strong association between DXAmeasured arm LST, MRI-measured arm SM, and grip strength. These findings support the use of DXA as a measure of functional tissue mass.