Multimodal Functional Assessment of Asymmetries in Youth Soccer Players: Study Protocol

Background: Youth soccer players are exposed to repeated unilateral loading during a period of rapid growth and neuromuscular maturation. These demands may contribute to postural deviations and inter-limb functional asymmetries that can influence movement control and mechanical efficiency. This study protocol aims to establish a standardized multimodal framework for assessing postural alignment, postural control, lower limb mechanical output, ankle dorsiflexion strength, support-limb neuromuscular activation, and contextual training and recovery variables in licensed youth soccer players aged 13 to 17 years. Methods: This prospective observational study will include 75 male youth soccer players recruited from S.C. Fotbal Club Ripensia Timișoara S.A. The primary outcome is the inter-limb asymmetry index derived from unilateral countermovement jump performance. Secondary outcomes include postural alignment, balance, bilateral jump performance, ankle dorsiflexion strength, and support limb electromyographic activity during the instep kick. Participants will complete a clinical evaluation questionnaire, including demographic, training, and recovery variables. Assessments will be conducted using the GaitON system, Kinvent K-Delta force platforms, K-Myo surface electromyography, and K-Pull dynamometry, before and after a regular training session. Biological maturation will be estimated using the Mirwald maturity offset method. Expected Results: The protocol will allow characterization of inter-limb asymmetries across postural, balance, jump, and electromyographic parameters. Conclusions: This protocol aims to provide a practical and standardized model for functional screening in youth soccer players.