Biceps Femoris Long-Head Architecture Assessed Using Different Sonographic Techniques

Purpose To assess the repeatability of, and measurement agreement between, four sonographic techniques used to quantify biceps femoris long head (BFlh) architecture: i) static-image with linear extrapolation technique; ii) extended field-of-view (EFOV) with linear ultrasound probe path (linear-EFOV) using either a straight or segmented analyses; and iii) EFOV with nonlinear probe path and segmented analysis (nonlinear-EFOV) to follow the complex fascicle trajectories. Methods Twenty individuals (24.4±5.7 years; 175±0.8 cm; 73±9.0 kg) without history of hamstring strain injury were tested in two sessions separated by 1-hour. An ultrasound scanner coupled with 6-cm linear probe was used to assess BFlh architecture in B-mode. Results The ultrasound probe was positioned at 52.0±5.0% of femur length and 57.0±6.0% of BFlh length. We found an acceptable repeatability when assessing BFlh fascicle length (ICC3,k = 0.86-0.95; SEM = 1.9-3.2 mm) and angle (ICC3,k = 0.86-0.97; SEM = 0.8-1.1o) using all sonographic techniques. However, the nonlinear-EFOV technique showed the highest repeatability (fascicle length ICC3,k = 0.95; fascicle angle, ICC3,k = 0.97). The static-image technique, which estimated 35.4±7.0% of the fascicle length, overestimated fascicle length (8-11%) and underestimated fascicle angle (8-9%) compared to EFOV techniques. Also, the rank order of individuals varied by ~15% between static-image and nonlinear-EFOV (segmented) when assessing the fascicle length. Conclusions Although all techniques showed good repeatability, absolute errors were observed using static-image (7.9±6.1 mm for fascicle length) and linear-EFOV (between 3.7±3.0 and 4.2±3.7 mm), probably because the complex fascicle trajectories were not followed. The rank order of individuals for fascicle length and angle were also different between static-image and nonlinear-EFOV, so different muscle function and injury risk estimates could likely be made when using this technique. Corresponding author: Sandro R. Freitas, Faculdade de Motricidade Humana, Universidade de Lisboa, Estrada da Costa, 1499-002, Cruz Quebrada, Dafundo, Portugal, sfreitas@fmh.ulisboa.pt. +351 91 785 99 38 The authors have declared no conflict of interests and that the study was not funded. Authors thank the study participants for their participation. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM. Accepted for Publication: 16 July 2018. © 2018 American College of Sports Medicine

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