2.4. Equipment and Data Analysis

In order to assess LAMs elasticity (shear modulus) and thickness, an Aixplorer ultrasound scanner (Supersonic Imagine, Aix-en-Provence, France) with a linear transducer array (2–10 MHz; SuperLinear 10-2, Vermon, Tours, France) has been used in the SWE mode. This mode is dedicated to elasticity measurements. All images were stored in the ultrasound scanner and calculated after collecting data from all participants. The thickness of the superficial fat layer was additionally measured in the thickest part of each image. The transducer was always positioned on the anterolateral wall, at the level of the umbilicus and parallel to the umbilicus. The transducer was orientated perpendicular to the long axis of the body (along the line of muscle fibers of TrA). Before the image was stored, the probe was adjusted to visualize the TrA myofascial junction. In further analysis, muscle and fat layer thickness from two images were used.

Examiners A and B performed measurements without any additional tools, whereas examiner C used a probe holder, specially prepared by the first author (GM), coupled with a pressure sensor. The pressure sensor (external S-Type load cell—DEE, Keli Sensing technology, Ningbo, China) was coupled with a force gauge FB1k (Axis, Gdansk, Poland). The force gauge was connected via a USB port to a computer and controlled by the AXIS FM v2.09 program (AXIS, Gdansk, Poland). This allowed the display of the force value (in Newtons) on screens in real time (Figure 1). The probe holder with the sensor was placed on an expansion beam by a magnetic holder. It allowed adjusting the probe in two dimensions without any restrictions. The probe was moved toward the subject’s body with a screw, and the compression force was registered by the pressure sensor and depicted on the force gauge.

General overview of the setup for the ultrasound examination with probe compression controlled. 1. Ultrasound probe. 2. External S-Type load cell connected to a force gauge (6). 3. Two-dimensional magnetic holder. 4. An expansion beam. 5. Precise screw actuator.