A physics-informed deep learning approach to predicting bilateral ground reaction forces and centre of pressure from a single forceplate during gait.

Background: Measuring bilateral ground reaction forces (GRFs) and centre of pressure (COP) is essential in gait analysis, requiring subjects to step each foot sequentially onto a separate forceplate. However, this requirement often causes multiple trial attempts, especially in patients with neuromusculoskeletal disorders. Consciously targeting the forceplates could also alter walking mechanics, leading to unnatural gait patterns.

Research Question: This study aimed to (1) develop a novel physics-informed residual recurrent neural network (PI-ResRNN) to predict bilateral GRF and COP during gait using data from a single forceplate and (2) evaluate its accuracy against ground truth obtained across subject groups of different ages and pathologies.

Methods: Forceplate data from 315 participants, namely healthy participants and patients with six types of neuromusculoskeletal disorders, was collected. Data from 6765 trials was used to train and validate the PI-ResRNN model to decompose GRF and COP for each foot during the double-contact phase of walking. Model-predicted COP and GRFs were evaluated against the ground truth using root-mean-square errors (RMSE) and relative RMSE (rRMSE), respectively.

Results: All predicted variables from the PI-ResRNN model demonstrated high consistency with the ground truth, with mean rRMSE values below 0.34 %, 0.38 %, and 0.56 % in the vertical, anteroposterior, and mediolateral GRFs, respectively, and mean RMSE values for COP below 3.0 mm. The model effectively identified statistical between-group differences compared with the ground truth.

Significance: The proposed model provides a practical and accurate approach for obtaining bilateral GRF and COP using a single forceplate, benefiting gait analysis in populations with mobility impairments.