Regional skeletal muscle measurement: evaluation of new dual-energy X-ray absorptiometry model

Although there is growing interest in studying muscle distribution, regiona l skeletal muscle (SM) mass measurement methods remain limited. The aim of the present study was to develop a new dual-energy X-ray absorptiometry (DE XA) model for estimating regional adipose tissue-free skeletal muscle mass (AT-free SM). Relationships were derived from Reference Man data between ti ssue-system-level components (i.e.,AT-free SM, AT, skeleton, and skin) and molecular-level components including fat-free soft tissue, fat, and bone mi neral. The proposed DEXA-SM model was evaluated by multiscan computerized a xial tomography (CT). Twenty-seven male subjects [age, 36 +/- 12 (SD) yr; b ody mass, 73.2 +/- 12.4 kg; 20 were healthy, and 7 had acquired immunodefic iency syndrome] completed DEXA. and CT studies. Identical landmarks for DEX A and CT measurements were selected in three regions, including calves, thi ghs, and forearms. There was a strong correlation for AT-free SM estimates between the new DEXA and CT methods (e.g., sum of three regions, r = 0.86, P < 0.001). RegionalAT-free SM measured in the 27 subjects by DEXA and CT, respectively, were 3.44 +/- 0.60 and 3.47 +/- 0.55 kg (difference 0.9%, P > 0.05) for calves, 10.49 +/- 1.77 and 10.05 +/- 1.79 kg (difference 4.4%, P < 0.05) for thighs, 1.36 +/- 0.49 and 1.20 +/- 0.41 kg (difference 13.3%, P < 0.01) for forearms, and 15.29 +/- 2.33 and 14.72 +/- 2.33 kg (differenc e 3.9%, P < 0.05) for the sum all three regions. Although the suggested DEX A-SM model needs minor refinements, this is a promising in vivo approach fo r measurement of regional SM, because DEXA is widely available, relatively inexpensive, and radiation exposure is low.