Longitudinal Changes in Isometric Trunk and Pelvic Strength Balance, Functional Movement and Muscle Imbalance During...

Background: Trunk and pelvic strength balance and functional movement quality are relevant factors for musculoskeletal health and injury-prevention monitoring in youth soccer players. Aim: This study aimed to evaluate longitudinal changes in isometric trunk and pelvic strength balance, functional movement quality, and selected muscle imbalance indicators during a physiotherapy-based strengthening programme in adolescent male soccer players. Methods: A longitudinal single-group repeated-measures study was conducted in male soccer players aged 12-18 years. Isometric strength balance was assessed using the Dr. Wolff Back-Check system, and functional movement quality was evaluated using the Functional Movement Screen (FMS). Complete-case analyses were performed according to available repeated measurements. Results: FMS total scores improved across repeated assessments, whereas the global Back-Check score showed no significant longitudinal change. Component-level and imbalance analyses indicated reductions in adductor-abductor imbalance, and better FMS performance was moderately associated with lower adductor-abductor imbalance. Conclusions: Functional movement quality and selected muscle imbalance indicators demonstrated favorable longitudinal changes during the physiotherapy-based strengthening programme. These findings suggest that physiotherapy-oriented strengthening and movement-control exercises may contribute to improvements in functional movement quality and selected muscle balance indicators in adolescent male soccer players. However, the small repeated-measures subsamples and observational study design limit causal interpretation and generalizability.