Fig. 1

Measuring skeletal muscle area on L3 axial slice Computer-Tomography (CT) Image, Using the National Institutes of Health ImageJ. Radio density thresholds were selected to correlate with those of skeletal muscle, with lower and upper thresholds of − 29 and 150 Hounsfield units, respectively. A Outer perimeter of the abdominal muscles is first delineated (yellow tracing) and area calculated, B The process is repeated for the inner perimeter of abdominal muscles (yellow tracing), C Vertebral area is further excluded (yellow tracing). The difference between measures equates to the area of skeletal muscle at the L3 level