Anticipatory Effects On Forward Trunk Lean During Stop-Jump Landings In Recreationally Active Women

When landing dynamics are altered due to unanticipated tasks, athletes may face increased challenges in controlling trunk posture. Altered trunk posture during landing tasks may negatively influence risk of ACL injuries. This is particularly relevant for female athletes, who may be at a higher risk of ACL injuries during unanticipated landings. Understanding the influence of anticipation on forward trunk lean could inform interventions aimed at reducing injury risks in dynamic sports settings. PURPOSE: To explore the influence of anticipation on forward trunk lean angle during stop-jump landings in recreationally active females. METHODS: Five unanticipated and anticipated stop-jump tasks were completed by ten healthy, recreationally active female participants (26.2 ± 1.5 yrs; 65.5 ± 10.2 kg; 1.66 ± 5.1 m). A stop-jump task is a bilateral movement test in which an individual runs forward, abruptly stops, and then immediately jumps vertically or at an angle. It’s commonly used in biomechanics to analyze landing mechanics, knee loading, and movement patterns related to injury risk, especially for ACL injuries. A 12-camera motion capture system and a force platform were used to collect marker coordinates and GRF data. Trials were randomly selected using a computer-generated stimulus in a custom LabVIEW program. Timing gates were positioned 2 meters and 1 meter before the force plate, triggering the visual stimulus and ensuring a consistent entry speed of 3.75–4.25 m/s. Trunk lean angle was calculated based on marker trajectory data. Paired samples t-tests were used to assess trunk lean differences, and Cohen’s d effect sizes were used to determine the meaningfulness of the differences. RESULTS: There was no difference in trunk lean angles between anticipated (-30.3 ± 14.6°) and unanticipated (-32.3 ± 13.9°) stop-jump landing conditions (p = 0.49; d = 0.14). CONCLUSION: The findings suggest that anticipation does not alter forward trunk lean angle during stop-jump landings. The lack of difference between landing types implies that trunk control may remain stable across both conditions. This stability may result from neuromuscular mechanisms that maintain trunk posture in response to unexpected stimuli, helping to protect against lower extremity injury during bilateral landings.