Fan beam densitometer

DXA scans were conducted using a fan-beam densitometer (Hologic, Inc., Bedford, MA, USA) for measurement of whole body muscle mass and fat and bone mass. Appendicular muscle mass (ASM) was assessed by the sum of the muscle mass of upper and lower limbs, and ASM divided by weight (ASM/Wt, %) was used to analyze the absolute level of ASM.22 (link) LMM was defined as the lower 10% of gender-specific ASM/Wt (%), like the prevalence among Korean adults.23 (link) We think our study analyzed subjects with extremely LMM. Evaluation of the extremely reduced muscle mass group has more meaning because mild muscle mass reduction status can be easily changed with diet and exercise. Furthermore, adolescents mostly do not have comorbidities and health problems, so mild reduction of muscle was more easily compensated for than in the elderly. For the current large-scale, representative Korean study, obesity was defined as the waist circumference-to-height ratio (WHtR) being over 0.47 in both sexes.24

Whole-body muscle mass was measured using DXA with a fan-beam densitometer (Hologic, Bedford, MA, USA). DXA is the most widely used and appropriate method for evaluating body composition; however, in Asians, DXA tends to overestimate the appendicular muscle mass because of higher adiposity in these populations.14 (link)
In this study, low muscle mass was defined as a value of appendicular skeletal muscle mass (ASM) divided by height squared (kg/m²), which was lower than the lowest quintile for the older population from the KNHANES survey15 16 (link); the suggested cut-off value was 6.43 kg/m². Height-adjusted methods can be more useful than weight-adjusted methods for identifying and characterising muscle mass in Asian populations.