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Aim: Τo examine the inter- and intra-muscular differences in the anatomical cross-sectional area (CSA) of the quadricep muscles, using extended - field of view (EFOV) ultrasonography (US).Material and methods: Panoramic transverse US images of the thigh were acquired from 10 young participants at five different locations across the thigh, in two sessions, spaced a week apart. The CSA of the vastus medialis (VM), rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL) and tensor vastus intermedius (TVI) was quantified.Results: The intraclass correlation coefficients ranged from 0.75 to 0.97 and the standard error of measurement ranged from 0.78% to 6.61%, indicating high test-retest reliability. Analysis of the variance indicated that among the 5 quadriceps muscles the VL and the RF displayed the greater CSA proximally, the VI medially and the VM distally across the thigh (p <0.05). No differences in the quadriceps CSA measured with and without including the TVI were found (p >0.05).Conclusions: The EFOV US technique provides transverse scans of the quadriceps muscle in vivo and allowed a reliable and non-invasive determination of CSA at a low cost. Evaluation of CSA along the thigh largely depends on the measurement site. Future studies that examine the quadriceps CSA using EFOV after any form of intervention should consider changes of at least 6.5% as meaningful.

Background. There is growing evidence that the quadriceps muscle group includes a fifth head, the tensor of vastus intermedius (TVI). The purpose of this study was to quantify the anatomic cross-sectional area (CSA) of the TVI using ultrasound. Methods. Ultrasonography scans were taken from 21 young males and females at rest, at 0° (= full extension), 45° and at 90° of knee flexion and they were repeated a week after to establish reliability. Measurements of the CSA were obtained from the most proximal and the most distal part of the muscle belly and from three different parts toward the course of the tendon. Results. US evaluation of the CSA displayed high reliability with an intraclass coefficient (ICC 3,3 ) ranging from 0.85 to 0.99 and a standard error of measurement ranging from 0.0019 to 0,2789 mm 2 . Analysis of variance indicated that the TVI muscle belly was larger proximally than distally and it was smaller at full extension compared with greater flexion angles (p < 0.05). The tendon CSA was greater proximally than middle and distal measurement sites (p <0.05) but it did not differ between various knee flexion angles. Conclusions. Future studies on the quadriceps muscle function and morphology should include examination of the TVI.