Bilateral Asymmetry and the Relationship Between Unilateral Isokinetic Strength and Balance Performance in Male Adolescent Football Players
Authors:   Department of Physical Education and Sport, University of Madeira, Funchal, Portugal, França Cíntia ,   LARSYS, Interactive Technologies Institute, Funchal, Portugal,   Research Center in Sports Sciences, Health Sciences, and Human Development (CIDESD), Vila Real, Portugal, Martins Francisco ,   Department of Physical Education and Sport, University of Madeira, Funchal, Portugal,   LARSYS, Interactive Technologies Institute, Funchal, Portugal, Martinho Diogo ,   University of Coimbra, Research Unit for Sport and Physical Education (CIDAF), Faculty of Sport Sciences and Physical Education, Coimbra, Portugal, Ihle Andreas ,   Department of Psychology, University of Geneva, Geneva, Switzerland,   Center for the Interdisciplinary Study of Gerontology and Vulnerability, University of Geneva, Geneva, Switzerland,   Swiss National Centre of Competence in Research LIVES—Overcoming Vulnerability: Life Course Perspectives, Lausanne, Switzerland, Marques Adilson ,   CIPER, Faculty of Human Kinetics, University of Lisbon, Lisbon, Portugal,   ISAMB, Faculty of Medicine, University of Lisbon, Lisbon, Portugal, Sarmento Hugo ,   University of Coimbra, Research Unit for Sport and Physical Education (CIDAF), Faculty of Sport Sciences and Physical Education, Coimbra, Portugal, Clemente Manuel ,   Escola Superior Desporto e Lazer, Instituto Politécnico de Viana do Castelo, Rua Escola Industrial e Comercial de Nun’Álvares, Viana do Castelo, Portugal,   Instituto de Telecomunicações, Delegação da Covilhã, Lisboa, Portugal, Przednowek Krzysztof ,   Institute of Physical Culture Sciences, Medical College, University of Rzeszów, Rzeszów, Poland, Campos Pedro ,   LARSYS, Interactive Technologies Institute, Funchal, Portugal,   Department of Informatics Engineering and Interactive Media Design, University of Madeira, Funchal, Portugal,   WoWSystems Informática Lda, Funchal, Portugal, Gouveia Élvio Rúbio ,   Department of Physical Education and Sport, University of Madeira, Funchal, Portugal,   LARSYS, Interactive Technologies Institute, Funchal, Portugal,   Center for the Interdisciplinary Study of Gerontology and Vulnerability, University of Geneva, Geneva, Switzerland
Published: October 2023

Muscle strength and balance ability have been related to injury prevention and game actions performance in football. The aims of this study are twofold: (1) to examine bilateral asymmetries in isokinetic strength and balance assessments, and (2) to evaluate the relationship between muscle strength and balance measures. Eighty-eight male adolescent football players were assessed for body composition (InBody 770), isokinetic strength (Biodex System 4 Pro Dynamometer), and balance performance (Biodex Balance System). Paired samples t-tests were conducted to determine bilateral differences in strength and balance. Pearson correlations and multiple linear regression analyses evaluated the relationship between strength and balance. No significant bilateral strength differences were observed in knee flexors (KF) and knee extensors (KE) peak torque (PT) scores. No bilateral differences were found for balance measures, except in the lateromedial stability index, which was better while performing with the preferred leg (p ≤ 0.01; d = 0.29). Significant correlations were found between KE PT and balance tasks (p ≤ 0.01). KF and KE PT shared between 18 and 22% of the common variance in the overall stability index in the non-preferred and preferred leg, respectively. Monitoring strategies of bilateral asymmetries may be crucial to enhance performance in tasks underpinned by unilateral movements, such as changes of direction and sprints, and to identify players at risk of injury. Adopting these strategies during the early stages of football training might be crucial for players’ long-term development.