{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,29]],"date-time":"2026-10-29T18:30:40Z","timestamp":1793298640414,"version":"4.5.0"},"reference-count":40,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,10,3]],"date-time":"2025-10-03T00:00:00Z","timestamp":1759449600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Physiol."],"abstract":"Background<\/jats:title>The aim of our study was analyze the bilateral strength balance of the knee extensor and flexor muscles in female soccer players.<\/jats:p><\/jats:sec>Methodology<\/jats:title>Participated in this study twenty-three professional female soccer players. The volunteer participants of the study were eligibly if: (a) signing of informed consent, (b) 5 years of sporting experience as a soccer player and have experience with training and evaluation of muscle strength in the lower limb, (c) participate in five weekly training sessions (d) no musculoskeletal pathology in the lower limbs 6 months prior to the evaluation date. The assessment was performed unilaterally, with peak muscle strength values recorded using the FEMD device software at a constant velocity of 0.4 m s-1<\/jats:sup>. The range of motion (ROM) was 90\u00b0\u20130\u00b0 of joint extension in the sitting position and 150\u00b0\u201390\u00b0 of flexion in the prone position. Each participant was required to perform their maximum effort for all repetitions.<\/jats:p><\/jats:sec>Results<\/jats:title>Bilateral strength balance measurements were obtained in the range of 10.68%\u201313.80% for maximum muscle strength in knee extension and 13.27%\u201315.21%. No significant differences (p<\/jats:italic> &gt; 0.05) were found in the comparison of independent means for maximum muscle strength between the knee extension and flexion in the concentric and eccentric phases. Significant differences (p<\/jats:italic> &lt; 0.01) and small ES (ES &lt; 3.32) were found in peak muscle strength measurements of the dominant and non-dominant lower extremity in the unilateral comparison of the extensor muscle and the flexor muscle group in the concentric and eccentric phase.<\/jats:p><\/jats:sec>Conclusion<\/jats:title>In the analysis of bilateral strength balance, lower indices are presented in the knee extensor compared to the flexor, these bilateral indices would reveal intrinsic and extrinsic risk factors for musculoskeletal injuries in the hamstring muscles and anterior cruciate ligament of professional soccer players.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fphys.2025.1681804","type":"journal-article","created":{"date-parts":[[2025,10,3]],"date-time":"2025-10-03T05:30:00Z","timestamp":1759469400000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["Bilateral strength balance of knee extensor and flexor muscles in female soccer players"],"prefix":"10.3389","volume":"16","author":[{"given":"Oscar","family":"Andrades-Ram\u00edrez","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Ulloa-D\u00edaz","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luis","family":"Romero-Vera","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bryan","family":"Alfaro-Castillo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gustavo","family":"Mu\u00f1oz-Bustos","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carlos","family":"Jorquera-Aguilera","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Claudio","family":"Carvajal-Parodi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luis-Javier","family":"Chirosa-R\u00edos","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2025,10,3]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"e14000","DOI":"10.7717\/peerj.14000","article-title":"Determining the hip joint isokinetic muscle strength and range of motion of professional soccer players based on their field position","volume":"10","author":"AlTaweel","year":"2022","journal-title":"PeerJ"},{"key":"B2","doi-asserted-by":"publisher","first-page":"1542492","DOI":"10.3389\/fphys.2025.1542492","article-title":"Intra-session reliability of knee flexion-extension muscle strength monitored using a functional electromechanical dynamometer in female soccer players","volume":"16","author":"Andrades-Ram\u00edrez","year":"2025","journal-title":"Front. Physiology"},{"key":"B4","doi-asserted-by":"publisher","first-page":"135","DOI":"10.2478\/hukin-2020-0058","article-title":"Lower-limb muscle strength, anterior-posterior and inter-limb asymmetry in professional, elite academy and amateur soccer players","volume":"77","author":"Beato","year":"2021","journal-title":"J. Hum. Kinet."},{"key":"B5","doi-asserted-by":"publisher","first-page":"1135","DOI":"10.1080\/02640414.2017.1361894","article-title":"Effects of inter-limb asymmetries on physical and sports performance: a systematic review","volume":"36","author":"Bishop","year":"2018","journal-title":"J. Sports Sci."},{"key":"B6","doi-asserted-by":"publisher","first-page":"129","DOI":"10.3390\/sports9090129","article-title":"Intra- and inter-limb strength asymmetry in soccer: a comparison of professional and Under-18 players","volume":"9","author":"Bishop","year":"2021","journal-title":"Sports"},{"key":"B7","doi-asserted-by":"publisher","first-page":"56","DOI":"10.1519\/JSC.0000000000002544","article-title":"Vertical and Horizontal asymmetries are related to Slower sprinting and jump performance in elite Youth female soccer players","volume":"35","author":"Bishop","year":"2021","journal-title":"J. Strength Cond. Res."},{"key":"B8","doi-asserted-by":"publisher","first-page":"204","DOI":"10.3390\/sports10120204","article-title":"Knee isokinetic profiles and Reference values of professional female soccer players","volume":"10","author":"Br\u00edgido-Fern\u00e1ndez","year":"2022","journal-title":"Sports"},{"key":"B42","doi-asserted-by":"publisher","first-page":"12900","DOI":"10.1038\/s41598-022-17245-5","article-title":"Leg dominance and performance in change of directions tests in young soccer players","volume":"12","author":"Clemente","year":"2022","journal-title":"Scientific Reports"},{"key":"B9","doi-asserted-by":"publisher","first-page":"1291","DOI":"10.3390\/ijerph20021291","article-title":"Dynamometric strength profile of hip muscles in Youth soccer players","volume":"20","author":"Contreras-D\u00edaz","year":"2023","journal-title":"Int. J. Environ. Res. Public Health"},{"key":"B10","doi-asserted-by":"publisher","first-page":"64","DOI":"10.3390\/sports9050064","article-title":"Reliability of the Single-leg, Medial countermovement jump in Youth Ice Hockey players","volume":"9","author":"Donskov","year":"2021","journal-title":"Sports"},{"key":"B11","doi-asserted-by":"publisher","first-page":"520","DOI":"10.1519\/JSC.0000000000002327","article-title":"Asymmetries in isometric force-Time Characteristics are not Detrimental to change of direction speed","volume":"32","author":"Dos\u2019Santos","year":"2018","journal-title":"J. Strength Cond. Res."},{"key":"B12","doi-asserted-by":"publisher","first-page":"357","DOI":"10.1590\/1517-869220184985","article-title":"Impact of competitive level and age on the strength and asymmetry of young soccer players","volume":"24","author":"Ferreira","year":"2018","journal-title":"Rev. Bras. Med. Do Esporte"},{"key":"B13","doi-asserted-by":"publisher","first-page":"109","DOI":"10.1016\/j.apunts.2013.05.003","article-title":"An\u00e1lisis de los factores de riesgo neuromusculares de las lesiones deportivas","volume":"48","author":"Fort-Vanmeerhaeghe","year":"2013","journal-title":"Apunts. Med. l\u2019Esport"},{"key":"B14","first-page":"364","article-title":"Lower limb strength in professional soccer players: profile, asymmetry, and training age","volume":"9","author":"Fousekis","year":"2010","journal-title":"J. Sports Sci. and Med."},{"key":"B15","doi-asserted-by":"publisher","first-page":"204","DOI":"10.1016\/j.ptsp.2021.03.001","article-title":"Does lower-limb asymmetry increase injury risk in sport? A systematic review","volume":"49","author":"Helme","year":"2021","journal-title":"Phys. Ther. Sport"},{"key":"B16","doi-asserted-by":"publisher","first-page":"41","DOI":"10.1519\/R-18795.1","article-title":"Effect of hamstring-emphasized resistance training on hamstring: quadriceps strength ratios","volume":"21","author":"Holcomb","year":"2007","journal-title":"J. Strength Cond. Res."},{"key":"B17","first-page":"49","article-title":"Linear models and effect magnitudes for research, clinical and practical applications","volume":"14","author":"Hopkins","year":"2010","journal-title":"Sportscience"},{"key":"B18","doi-asserted-by":"publisher","first-page":"686","DOI":"10.1080\/02640414.2023.2235157","article-title":"Influence of unilateral and bilateral knee extension fatigue protocols on inter-limb asymmetries assessed through countermovement jumps","volume":"41","author":"Janicijevic","year":"2023","journal-title":"J. Sports Sci."},{"key":"B19","doi-asserted-by":"publisher","first-page":"113145","DOI":"10.1016\/j.physbeh.2020.113145","article-title":"Behavior of the muscle quality index and isometric strength in elderly women","volume":"227","author":"Jerez-Mayorga","year":"2020","journal-title":"Physiology Behav."},{"key":"B20","doi-asserted-by":"publisher","first-page":"180","DOI":"10.1186\/s13102-024-00961-y","article-title":"The isometric and isokinetic knee extension and flexion muscle strength profile of elite soccer players","volume":"16","author":"Keytsman","year":"2024","journal-title":"BMC Sports Sci. Med. Rehabilitation"},{"key":"B21","doi-asserted-by":"publisher","DOI":"10.26773\/smj.201002","article-title":"Electromyography comparisons of lower extremity muscles during maximum velocity Instep soccer Kicks","volume":"18","author":"Kumar","year":"2020","journal-title":"Sport Mont."},{"key":"B22","doi-asserted-by":"publisher","first-page":"3557","DOI":"10.1519\/JSC.0000000000000588","article-title":"Relationship between unilateral jumping ability and asymmetry on Multidirectional speed in Team-sport athletes","volume":"28","author":"Lockie","year":"2014","journal-title":"J. Strength Cond. Res."},{"key":"B23","first-page":"483","article-title":"Muscle contraction velocity: a Suitable Approach to analyze the functional adaptations in elite soccer players","volume":"15","author":"Loturco","year":"2016","journal-title":"J. Sports Sci. and Med."},{"key":"B24","doi-asserted-by":"publisher","first-page":"1339","DOI":"10.4067\/S0717-95022016000400027","article-title":"Unilateral and Ipsilateral strength asymmetries in elite Youth soccer players with Respect to muscle group and limb dominance","volume":"34","author":"Maly","year":"2016","journal-title":"Int. J. Morphol."},{"key":"B25","doi-asserted-by":"publisher","first-page":"1370","DOI":"10.1519\/JSC.0b013e318265a3c8","article-title":"Analysis of lower limb asymmetries by isokinetic and vertical jump tests in soccer players","volume":"27","author":"Menzel","year":"2013","journal-title":"J. Strength Cond. Res."},{"key":"B26","doi-asserted-by":"publisher","first-page":"404","DOI":"10.3389\/fphys.2015.00404","article-title":"Sprint Acceleration Mechanics: the Major role of hamstrings in Horizontal force production","volume":"6","author":"Morin","year":"2015","journal-title":"Front. Physiology"},{"key":"B27","doi-asserted-by":"publisher","first-page":"1298159","DOI":"10.3389\/fphys.2024.1298159","article-title":"The association between unilateral and bilateral performance-related measures in elite female soccer players: a multifaceted investigation","volume":"15","author":"Paravlic","year":"2024","journal-title":"Front. Physiology"},{"key":"B28","doi-asserted-by":"publisher","first-page":"199","DOI":"10.5114\/biolsport.2019.85453","article-title":"Adolescent female soccer players\u2019 soccer-specific warm-up effects on performance and inter-limb asymmetries","volume":"36","author":"Pardos-Mainer","year":"2019","journal-title":"Biol. Sport"},{"key":"B29","doi-asserted-by":"publisher","first-page":"1147","DOI":"10.1123\/ijspp.2019-0265","article-title":"Effects of Combined strength and power training on physical performance and Interlimb asymmetries in Adolescent female soccer players","volume":"15","author":"Pardos-Mainer","year":"2020","journal-title":"Int. J. Sports Physiology Perform."},{"key":"B30","doi-asserted-by":"publisher","first-page":"1080","DOI":"10.3390\/medicina58081080","article-title":"Anterior-posterior and inter-limb lower body strength asymmetry in soccer, Basketball, futsal, and Volleyball players","volume":"58","author":"Parpa","year":"2022","journal-title":"Medicina"},{"key":"B31","doi-asserted-by":"publisher","first-page":"521","DOI":"10.5114\/biolsport.2023.118022","article-title":"Effects of 6 weeks in-season flywheel squat resistance training on strength, vertical jump, change of direction and sprint performance in professional female soccer players","volume":"40","author":"Pecci","year":"2023","journal-title":"Biol. Sport"},{"key":"B32","doi-asserted-by":"publisher","first-page":"176","DOI":"10.1177\/1754337120984883","article-title":"Reliability and concurrent validity of a functional electromechanical dynamometer device for the assessment of movement velocity","volume":"235","author":"Rodriguez-Perea","year":"2021","journal-title":"Proc. Institution Mech. Eng. Part P J. Sports Eng. Technol."},{"key":"B34","doi-asserted-by":"publisher","first-page":"11","DOI":"10.1186\/s40798-019-0185-0","article-title":"Alternative methods of determining hamstrings-to-quadriceps ratios: a Comprehensive review","volume":"5","author":"Ruas","year":"2019","journal-title":"Sports Med. - Open"},{"key":"B35","doi-asserted-by":"publisher","first-page":"79","DOI":"10.37190\/ABB-01513-2019-03","article-title":"Asymmetry of lower limb strength and jumping ability of young soccer players","volume":"22","author":"Rutkowska-Kucharska","year":"2020","journal-title":"Acta Bioeng. Biomechanics"},{"key":"B36","doi-asserted-by":"publisher","first-page":"1685","DOI":"10.23736\/S0022-4707.22.13498-5","article-title":"The effects of the FIVE futsal injury prevention program on lower limb muscle strength among young futsal players","volume":"62","author":"Saryono","year":"2022","journal-title":"J. Sports Med. Phys. Fit."},{"key":"B37","doi-asserted-by":"publisher","first-page":"Article6","DOI":"10.29359\/BJHPA.16.4.06","article-title":"The impact of asymmetry in lower limb muscle strength and power on straight-line running speed in female soccer players","volume":"16","author":"Skalski","year":"2024","journal-title":"Baltic J. Health Phys. Activity"},{"key":"B38","first-page":"9","article-title":"Unilateral and bilateral isokinetic knee strength indices in professional soccer players","volume":"37","author":"Vel\u00e1zquez","year":"2020","journal-title":"Arch. Med. Del Deporte"},{"key":"B39","doi-asserted-by":"publisher","first-page":"171","DOI":"10.3390\/sports10110171","article-title":"Test\u2013retest reliability and sensitivity of common strength and power tests over a period of 9 Weeks","volume":"10","author":"Venegas-Carro","year":"2022","journal-title":"Sports"},{"key":"B40","doi-asserted-by":"publisher","first-page":"2191","DOI":"10.1001\/jama.2013.281053","article-title":"World Medical association Declaration of Helsinki: Ethical Principles for Medical research involving Human Subjects","volume":"310","year":"2013","journal-title":"JAMA"},{"key":"B41","doi-asserted-by":"publisher","first-page":"105","DOI":"10.1080\/00913847.2019.1642808","article-title":"Knee isokinetic muscle strength and balance ratio in female soccer players of different age groups: a cross-sectional study","volume":"48","author":"Zimermann","year":"2020","journal-title":"Physician Sportsmed."}],"container-title":["Frontiers in Physiology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2025.1681804\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,3]],"date-time":"2025-10-03T05:30:01Z","timestamp":1759469401000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2025.1681804\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,10,3]]},"references-count":40,"alternative-id":["10.3389\/fphys.2025.1681804"],"URL":"https:\/\/doi.org\/10.3389\/fphys.2025.1681804","relation":{},"ISSN":["1664-042X"],"issn-type":[{"value":"1664-042X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,10,3]]},"article-number":"1681804"}}