Muscle Quality and Subcutaneous Adipose Tissue in the Rectus Femoris and Rectus Abdominis Muscles: Ultrasound Evaluation and Functional Correlation in Older Adults

Ultrasound Assessment of the Rectus Femoris Muscle

The rectus femoris muscle was assessed using B-mode ultrasound imaging, following SARCUS group recommendations. Participants were positioned supine for 5 minutes prior to imaging to ensure fluid redistribution. A linear transducer (12 MHz) was used with neutral probe angle and minimal pressure. The anatomical landmark was the midpoint between the greater trochanter and the upper pole of the patella. Measurements included muscle thickness, pennation angle, fascicle length, echo intensity, cross-sectional area, and subcutaneous fat thickness. Images were taken in both transverse and longitudinal planes. Three measurements were taken per view to ensure accuracy.

Time frame: At a single assessment visit

Ultrasound Assessment of the Rectus Abdominis Muscle

The rectus abdominis muscle was assessed using the same ultrasound equipment and imaging protocol as for the rectus femoris. The anatomical reference point was located 3 cm lateral to the umbilicus, as per SARCUS group guidance. Images were acquired in both transverse and longitudinal planes. Measurements included muscle thickness, echo intensity, anatomical cross-sectional area, and subcutaneous fat thickness. Three measurements were taken per view to ensure reliability.

Time frame: At a single assessment visit