Citation: Ðor ¯ devi´ c, S.; Rozman, S.; Zupet, P.; Dopsaj, M.; Maffulli, N. Tensiomyography Allows to Discriminate between Injured and Non-Injured Biceps Femoris Muscle. Biology 2022, 11, 746. https:// doi.org/10.3390/biology11050746 Academic Editor: Carlo Reggiani Received: 26 January 2022 Accepted: 10 May 2022 Published: 13 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). biology Article Tensiomyography Allows to Discriminate between Injured and Non-Injured Biceps Femoris Muscle Sr ¯ dan Ðor ¯ devi´ c 1, *, Sergej Rozman 1 , Petra Zupet 2 , Milivoj Dopsaj 3,4 and Nicola Maffulli 5,6,7 1 TMG-BMC, Štihova ulica 24, 1000 Ljubljana, Slovenia; sergej.rozman@tmg.si 2 Institute for Medicine and Sports, Cesta na Poljane 24, 1000 Ljubljana, Slovenia; petra.zupet@i-ms.si 3 Faculty of Sport and Physical Education, University of Belgrade, 11000 Belgrade, Serbia; milivoj.dopsaj@fsfv.bg.ac.rs 4 Department of Physical Education and Health, Institute of Sport, Tourism and Service, South Ural State University, Prospekt Lenina 76, 454080 Chelyabinsk, Russia 5 Centre for Sports and Exercise Medicine, Barts and the London School of Medicine and Dentistry, Mile End Hospital, 275 Bancroft Road, London E1 4DG, UK; n.maffulli@qmul.ac.uk 6 School of Pharmacy and Bioengineering, Keele University School of Medicine, Stoke-on-Trent ST4 7QB, UK 7 Department of Musculoskeletal Disorders, Faculty of Medicine and Surgery, University of Salerno, Via S. Allende, 84081 Baronissi, Italy * Correspondence: srdjand@tmg.si; Tel.: +386-41-672-601 Simple Summary: The hamstring muscle group is the most frequently injured muscle group in non- contact muscle injuries involving high-speed running sports. The biceps femoris (BF) muscle has the highest injury incidence. Clinical assessments and magnetic resonance imaging (MRI) are routinely used to diagnose a given injury. We tested the possibilities of a new technology—tensiomyography—as a potential screening test (diagnostic and classification purposes) to assess the functional differences between injured and non-injured BF muscles. The results show that tensiomyography has a high predictive ability to discriminate between injured and non-injured BF non-invasively and functionally and that it can be reliably used as a complementary screening test in the diagnosis of BF injuries. Abstract: The hamstring muscle group is the most frequently injured muscle group in non-contact muscle injuries in sports involving high-speed running. A total of 84% of hamstring injuries affect the biceps femoris (BF) muscle. Clinical assessments and magnetic resonance imaging (MRI) are routinely used for diagnosis and plan management. MRI-negative scans for clinically diagnosed hamstring injuries range from 14% to 45%. We tested the hypothesis that the functional differences between injured and non-injured BF assessed by tensiomyography can be used for diagnostic and classification purposes. We compared an injured group of 53 international-level soccer players and sprinters with 53 non-injured international-level soccer players and sprinters of both sexes. Comparing the injured vs. non-injured athletes and the left vs. right side in all of the athletes, we used the percentage of absolute differences in the BF contraction time (Tc) to classify non-injured and injured BF muscles. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) and the precision–recall curve (PRC) were used to measure the classification accuracy and to identify cut-off limits using the Tc differences. There was a very high ROC AUC value of 0.981 (SE = 0.009, p < 0.000), with 98.11% of the injured muscles being correctly classified (cut-off point 12.50% on Tc differences), and an AUPRC value of 0.981, with association classification criteria at >9.87. Tensiomyography has a high predictive ability to discriminate between injured and non-injured BF non-invasively and functionally. Keywords: biceps femoris injuries; tensiomyography; functional diagnostic; contraction time Biology 2022, 11, 746. https://doi.org/10.3390/biology11050746 https://www.mdpi.com/journal/biology