Introduction: Reactive side-step cutting manoeuvres are a common task linked to anterior cruciate ligament (ACL) injuries in Women’s Australian Football League (AFLW) matches. Knee loads associated with increased ACL loading and strain are typically elevated when performing unanticipated versus anticipated changes of direction. We explored knee joint moments and ground reaction forces (GRFs) in AFLW players when performing anticipated and unanticipated side-step cuts.
Methods: Eight AFLW players (age = 25.5 + 4.4y; height = 173.7 + 6.0cm; mass = 70.5 + 5.0kg) completed anticipated and unanticipated side-step cutting trials during which full-body three-dimensional kinematics and kinetics were recorded. The anticipated condition involved a side-step cut at 35-55 degrees with no reactive stimuli. The unanticipated condition involved players responding to a randomised visual stimulus directing them to perform one of three common Australian football movement tasks (i.e. side-step cut, stop-jump and straight run). Approach speed was monitored and controlled between the anticipated and unanticipated conditions. One dimensional statistical parametric mapping (SPM1D) paired t-tests were used to compare three-dimensional knee moments during weight acceptance (WA) phase and GRFs during the stance phase of the anticipated and unanticipated side-step cuts.
Results: Unanticipated side-stepping incurred reduced knee flexion and knee abduction moments during late WA (60%-97% of WA, p < 0.01 and 50%-76% of WA, p = 0.01; respectively). Braking and propulsive GRFs were altered across the majority of the stance phase (8%-91% of stance, p < 0.01), with unanticipated side-stepping resulting in reduced braking and elevated propulsive GRFs. Unanticipated side-stepping also resulted in reduced vertical GRFs in the early stance phase (12%-22% of stance, p < 0.01).
Discussion: We observed knee joint moments associated with reduced ACL loading in AFLW players when performing unanticipated side-stepping, contrasting to previous research on anticipatory effects on side-step cutting biomechanics. The AFLW players in this study appear to have employed a ‘cautious’ approach to the unanticipated side-step, as indicated by the reduced braking and vertical GRFs in the early stance phase of the cut. Despite controlling for approach speed, the altered GRF profile suggests players decelerated to a greater extent prior to performing the cut during the unanticipated condition. This provided a potentially protective outcome by lowering knee loads, but likely has negative performance implications (i.e. reduced cutting speed). An inability to consciously adopt this ‘cautious’ approach during on-field reactive scenarios may explain why ACL injuries occur during these movements in AFLW matches. AFLW ACL injury prevention programs may be enhanced with greater exposure to scenarios that replicate reactive match-play demands when aiming to improve side-step cutting biomechanics.
Summary
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Our study provides knowledge around the adaptive biomechanical strategy AFLW players use under reactive side-step cutting scenarios.
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Our findings can be used to design targeted elements within AFLW ACL injury prevention programs.
Conflict of Interest Statement: My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.
History
Alternative title
Anticipatory Effects on Side-Step Cutting Biomechanics in Women’s Australian Football League Players