Study Design Case-control study in a Research Lab.

Objectives 1) Investigate the kinematic difference during an anticipated and unanticipated jump landing tasks following a drop landing in individuals with Chronic Ankle Instability and Healthy Controls.

Background Chronic ankle instability (CAI) is a common condition following acute lateral sprains and has been associated with kinematic and kinetic differences during jumping and landing tasks. Previous research has shown differences in frontal and sagittal plane kinematics and kinetics during planned and controlled movement tasks. Injury, however, is more likely to occur during unplanned tasks. An unanticipated landing task may more accurately reflect the movement strategies taken during sport and athletic participation.

Methods and Measures Ten subjects have completed the study(CAI n=3, IdFAI: 22±5, FAAM-ADL: 77±11, FAAM-Sport: 76±4, Control n=3, IdFAI: 3±1, FAAM-ADL: 98±1, FAAM-Sport: 99±2). A 10 camera motion capture system (Vicon Motion Systems, Lake Forest, CA, USA) was used to capture 5 anticipated and 5 unanticipated bilateral drop landing tasks in 3 directions, right, up and left. The drop landing task was completed off of a 30 cm box placed half of the subject’s height from the forceplate. For all unanticipated trials, an arrow indicated the direction was randomly displayed on a screen 0.1 s after leaving the box. Data was analysed 250 ms prior and post ground contact. Comparisons were made between CAI and Controls in the three jump directions in both anticipated and unanticipated trials. Anticipated was also compared to unanticipated in both groups and both jump directions.

Results No differences were found between any of the current comparisons. With just 6 subjects more data needs to be collected to reach power.

Conclusions While, currently no statistical differences have been found. Assessing movement during unanticipated tasks reflects more sports specific and realistic tasks that lead to ankle joint injury.