BackgroundSarcopenia, defined as low muscle mass and low muscle strength and/or low physical performance, is affecting more and more people. The European Working Group on Sarcopenia in Older People has suggested the routine community screening. However, selecting the most suitable method to evaluate muscle mass to detect sarcopenia in community screening is a challenge. This study sought to analyze the correlation between ultrasound (US) measurements of the gastrocnemius muscle and low muscle mass, as defined by sarcopenia.MethodsOne hundred thirty-five elderly participants were enrolled. US measurements included muscle thickness (MT), fat thickness (FT), MT/body mass index (BMI), and MT/FT. The definition of low muscle mass was based on the proposal from the Asian Working Group for Sarcopenia, in which the cutoff values for low muscle mass were 7.0 kg/m2 for men and 5.4 kg/m2 for women using dual energy X-ray absorptiometry (DXA). The participants were divided into low and normal muscle mass groups. Participants with low muscle mass were divided into presarcopenia, sarcopenia, and severe sarcopenia groups.ResultsThose in the low muscle mass group were older and had lower weights and BMIs (P<0.05). In addition, MT and MT/BMI were lower in the low muscle mass group (P<0.05). Binary logistic regression analysis revealed that MT was the factor associated with low skeletal muscle mass (OR =0.001, P<0.001). ANOVA revealed that MT was not significantly different between subjects with presarcopenia, sarcopenia, and severe sarcopenia (F=1.69, P=0.192). Receiver operating characteristic curve analyses indicated that the cutoff value of the gastrocnemius MT for low muscle mass was 1.50 cm.ConclusionMT measured by US was identified as the factor associated with low skeletal muscle mass. Those with gastrocnemius MT less than 1.5 cm can be considered as low muscle mass.