The Use of The Opencap Framework to Estimate Bilateral Vertical Ground Reaction Forces During Jumping Tasks

A new open-source, web-based software called OpenCap, has proposed the use of smartphones to estimate three-dimensional kinematics and associated kinetics. This study investigated the validity of the OpenCap framework in its ability to estimate GRF. It was hypothesized that the OpenCap method would show no significant differences in its ability to estimate bilateral vertical GRF generated during jumping tasks when compared to force plates. Twenty participants performed three trials of four jump tasks while OpenCap recorded video from two smartphones and GRF data were collected using two force plates. Resultant kinematic data were input into a torque-driven model simulation to estimate GRF (GRFTORQUE) and input into OpenSim to calculate body COM acceleration to predict GRF (GRFCOM). Errors in GRF were quantified using RMSE, MAE, and R2. The GRFTORQUE method had an RMSE of 19% - 47% BW, MAE of 15% - 36% BW and R2 of 0.45 - 0.65 across the jump tasks. The GRFCOM method had an RMSE of 32% - 40% BW, MAE of 23% - 29% BW and R2 of 0.48 - 0.59 across single leg jumps. While these findings highlight the potential use of OpenCap for estimating GRF during jump tasks, they indicate the need for further improvement.