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DeMers MS, Hicks JL, Delp SL. Preparatory co-activation of the ankle muscles may prevent ankle inversion injuries. Journal of Biomechanics. (accepted) (2016)

Ankle inversion sprains are the most frequent acute musculoskeletal injuries occurring in physical activity. Interventions that retrain muscle coordination have helped rehabilitate injured ankles, but it is unclear which muscle coordination strategies, if any, can prevent ankle sprains. The purpose of this study was to determine whether coordinated activity of the ankle muscles could prevent excessive ankle inversion during a simulated landing on a 30 degree incline. We used musculoskeletal simulation to evaluate the efficacy of two strategies for coordinating the ankle evertor and invertor muscles during simulated landing scenarios: planned co-activation and stretch reflex activation with physiologic latency (60-millisecond delay). We developed a full-body musculoskeletal model and used it to generate simulations of a subject dropping and landing on an inclined surface with either coordination condition, systematically varying the intensity of evertor and invertor co-activity or stretch reflexes. Our simulations revealed that strong preparatory co-activation of the ankle evertors and invertors prior to ground contact prevented ankle inversion from exceeding injury thresholds by rapidly generating eversion moments after initial contact. Conversely, stretch reflexes were too slow to generate eversion moments before the simulations reached the threshold for inversion injury. These results suggest that training interventions to protect the ankle should focus on stiffening the ankle with muscle co-activation instead of increasing the speed or intensity of the evertor reflexes. The musculoskeletal models, controllers, software, and simulation results are freely available online, enabling others to reproduce the results and explore new injury scenarios and interventions.

This paper identifies that planned co-activation of the ankle invertors and evertors may protect the ankle from rapid inversion injuries, while even the fastest stretch reflexes in these muscle are likely too slow.

License: Controller plugins source code, Get everything in one archive, Models

The study described in this publication used musculoskeletal simulations to compare the capacity of planned invertor/evertor co-activation versus stretch reflexes with physiologic delay to prevent ankle inversion injuries. To achieve this, developed a novel model, muscle stretch controllers, and muscle reflex controllers for simulating landing in OpenSim. By freely providing the models, software plugins defining the controllers, and the resulting simulations, we hope to enable others to answer questions about landing control and injuries using simulations.

All models, data, and simulation results are provided in the downloads area of this project.

For software and sourcecode defining the novel stretch feedback controller and stretch reflex controller, see the related repository on GitHub.



Provides models, software plugins, and source code for simulating human landing with stretch controllers and reflex controllers to reproduce the findings of this publications. It also provides the simulation results as a launching point for future analyses.

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