The evaluation of skeletal muscle (SM) mass has significant clinical and research relevance in the diagnosis and management of conditions such as malnutrition, sarcopenia, sarcopenic obesity, and cancer cachexia. Dual-energy X-ray absorptiometry (DXA) is now the most widely used method for estimating SM mass; however, it does not directly measure SM but instead provides proxies that require careful interpretation.

A major issue in the field is the inconsistent and sometimes incorrect use of DXA-derived terminology in both scientific literature and clinical practice, leading to potential misdiagnoses and inaccurate research conclusions. This review highlights the importance of using proper terminology and the errors that arise when DXA-based estimates of SM mass are misrepresented.

Focusing on the appendicular regions, where most SM is located, we first describe the principles of DXA measurement, including its ability to quantify appendicular lean soft tissue (ALST) and appendicular lean mass (ALM) and their relationship to appendicular skeletal muscle (ASM). We then examine inconsistencies in manufacturer-reported DXA outputs and common reporting errors in the literature, particularly the interchangeable use of ALST and ASM.

Additionally, we present data demonstrating how these inconsistencies impact the clinical assessment of sarcopenia and influence population-level prevalence estimates. ALM refers to all non-fat components of the arms and legs, while ALST also removes bone mass.

Both measures include non-SM components and are, therefore, larger than SM. To address the use of these terms, we propose standardizing DXA terminology and reporting practices in both research and clinical settings.

We also highlight the importance of consistent terminology in other clinical and field-based methods of body composition assessment, including bioelectrical impedance analysis and 3-dimensional optical imaging. These recommendations will enhance the clarity of SM-related measures (e.g., ALST, ALM), improve diagnostic accuracy, and facilitate meaningful comparisons across studies.