title: Lower limb skeletal muscle mass: development of dual-energy X-ray absorptiometry prediction model.
abstract: Although magnetic resonance imaging (MRI) can accurately measure lower limb skeletal muscle (SM) mass, this method is complex and costly. A potential practical alternative is to estimate lower limb SM with dual-energy X-ray absorptiometry (DXA). The aim of the present study was to develop and validate DXA-SM prediction equations. Identical landmarks (i.e., inferior border of the ischial tuberosity) were selected for separating lower limb from trunk. Lower limb SM was measured by MRI, and lower limb fat-free soft tissue was measured by DXA. A total of 207 adults (104 men and 103 women) were evaluated [age 43 +/- 16 (SD) yr, body mass index (BMI) 24.6 +/- 3.7 kg/m(2)]. Strong correlations were observed between lower limb SM and lower limb fat-free soft tissue (R(2) = 0.89, P < 0.001); age and BMI were small but significant SM predictor variables. In the cross-validation sample, the differences between MRI-measured and DXA-predicted SM mass were small (-0.006 +/- 1.07 and -0.016 +/- 1.05 kg) for two different proposed prediction equations, one with fat-free soft tissue and the other with added age and BMI as predictor variables. DXA-measured lower limb fat-free soft tissue, along with other easily acquired measures, can be used to reliably predict lower limb skeletal muscle mass.
authors.affiliation: Obesity Research Center, Department of Medicine, St. Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons, New York, New York 10025, USA.
authors.forename: R
authors.initials: R
authors.lastname: Shih
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Heo
authors.forename: W
authors.initials: W
authors.lastname: Wang
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D005260:Female; D006801:Humans; D007866:Leg; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012727:Sex Characteristics