Biomechanical analysis of the knee joint during sidestepping: a fully immersive virtual reality approach to football defending scenarios

Traditional sidestepping experiment often relies on simplified visual stimuli that lack ecological validity. This study aimed to develop a fully immersive, football-specific virtual reality (VR) system to examine knee biomechanics during sidestepping in response to realistic visual stimuli. Twelve male collegiate footballers performed unanticipated sidestepping in response to a virtual footballer avatar executing either non-deceptive (VF-ND) or deceptive (VF-D) dribbling. Despite similar approach velocity and stance time, participants exhibited greater knee flexion angles and abduction and internal rotation moments in VF-D trials. Secondary analyses compared the results with previously reported arrow-preplanned (A-PP) and arrow-unplanned (A-UP) trials from the same participants. Approaching velocity decreased, and stance time increased in the following order: A-PP, VF-ND, VF-D and A-UP. Knee flexion angles and abduction moments increased, while peak internal rotation moments decreased in the same order. These findings suggested that the VR-based approach imposed more realistic visuospatial and temporal constraints than traditional methods, enhancing ecological validity. As in real environment, players in VR can perceive subtle cues, distinguish deceptive from non-deceptive actions and adapt their movements accordingly. Practitioners should design their protocols to resemble real-world scenarios as closely as possible and interpret the biomechanical outcomes cautiously when comparing across different visual stimuli.