Effects of increasing cognitive demands through expanding movement options on biomechanics during changes of direction in female football players.

Anterior cruciate ligament injuries often occur during changes-of-direction (CODs), particularly when combined with cognitively demanding decision-making tasks. This study investigated the effects of increasing movement options during CODs in response to a real opponent on whole-body biomechanics in female football players. Twenty-nine female football players (15 with high and 14 with low expertise) performed 90° CODs in response to a real opponents' action under four conditions: anticipated with one option (ANT-1), unanticipated with two (UNANT-2), three (UNANT-3) or four (UNANT-4) movement options. Three-dimensional motion analysis captured whole-body biomechanics at initial contact and during weight acceptance. Continuous biomechanical data were analyzed using a statistical parametric mapping approach. No significant condition effects were observed for peak knee mechanics. However, at initial contact the pelvis was significantly less tilted and rotated towards the running direction in the UNANT-4 condition than in ANT-1. The hip was significantly more abducted and internally rotated in all unanticipated CODs. Furthermore, trunk rotation to the cutting leg was reduced in all unanticipated conditions compared to ANT-1. No significant differences were found between expertise groups. Increasing cognitive demands in a simulated match-play scenario primarily influenced proximal segment biomechanics during CODs in female football players. The authors therefore recommend integrating whole-body control and cognitively demanding stimuli into testing and injury prevention strategies.