Relationship between Dual-Energy X-Ray Absorptiometry-Derived Appendicular Lean Tissue Mass and Total Body Skeletal Muscle Mass Estimated by Ultrasound

Dual-energy X-ray absorptiometry (DXA) is an attractive method for evaluating sarcopenia, age-related loss of skeletal muscle mass and function, using appendicular lean tissue (aLT) mass for criteria of diagnosis, although minimal radiation is exposed. Skeletal muscle (SM) mass can be estimated by using ultrasound-measured muscle thickness (MTH). However, the association between these two methods is unclear. To examine the relationship between DXA-derived aLT mass and total body SM mass estimated by ultrasound, thirty-six healthy adults (18 men and 18 women) aged 19 - 65 years participated in this study. Ultrasound-measured muscle thickness was used to estimate the total SM mass. DXA was used to estimate whole body and regional body composition, and aLT mass was considered equivalent to the sum of lean tissue in both the right and left arms and legs. Total SM mass (26.3 ± 4.4 kg for men and 15.7 ± 2.6 kg for women) estimated by ultrasound was similar to DXA-estimated aLT mass (24.5 ± 3.8 kg for men and 15.7 ± 2.7 kg for women). There was a strong correlation between DXA-measured aLT mass and total SM mass estimated by ultrasound in men (r = 0.927, n = 18) and women (r = 0.931, n = 18) as well as overall sample (r = 0.975, n = 36). The ratio of total SM mass to aLT mass was 1.07 for men and 1.00 for women. These results suggest that DXA-derived aLT mass can be accurately predicted from ultrasound estimated total SM mass, although the predicted value may underestimate in men (approximately 7% at the group level).