589 FO26 – Individualized sidestep cutting technique feedback in handball under consideration of performance – best of both worlds for ACL injury prevention?

Background Non-contact anterior cruciate ligament injuries during sidestep cutting typically occur rapidly after contact between the foot and the ground with little time for athletes to correct movement patterns. Technique feedback aiming at safe posture at initial ground contact might prove valuable in reducing frontal plane knee joint loading. Objective To assess the immediate effects of individualized technique feedback during sidestep cutting on selected technique variables and peak external knee abduction moments. Design Interventional study. Setting Biomechanical laboratory. Participants 48 adolescent female elite handball players. Interventions Players performed three preplanned handball-specific sidestep cuts on each leg while 3D biomechanics were recorded. Following these cuts, players received tailored technique feedback on their foot strike angle, knee valgus angle, or vertical impact velocity based on cut-off values drawn from an existing data set. If multiple technique variables exceeded their cut-off, variable selection was based on its established relation with performance. Following feedback, three more cuts on each leg were performed. Main Outcome Measurements Peak external knee abduction moment and selected technique variables. Results Feedback aimed at pronounced forefoot landings and reduced knee valgus angles improved technique immediately (+12.7°, p < .001, Figure a and +1.5°, p = .022, Figure b, respectively) and reduced peak external knee abduction moments (-13.4%, p = .003, Figure d and -17.1%, p = .020, Figure e, respectively). Feedback aimed at reduced vertical impact velocities improved technique immediately (-19.0%, p = .010; Figure c); however, peak external knee abduction moments were unaffected (p = .328; Figure f), owing to the variable's unclear relation with technique and therefore lowest priority and smallest sample size. Conclusions Individualized feedback can induce sidestep cutting technique changes immediately, thereby successfully decreasing peak external knee abduction moments and potentially injury risk. Improving technique without sacrificing performance might prove attractive to coaches and players alike.