A method for determining a hand force and a ground reaction force for a musculoskeletal body of a subject includes obtaining video data for the musculoskeletal body during an action taken by the subject, generating, for each frame of the video data, three-dimensional pose data for the subject based on a three-dimensional skeletal model, and determining the hand force and the ground reaction force based on the three-dimensional pose data. Determining the hand force and the ground reaction force includes implementing a reconstruction of the hand force and the ground reaction force based on the three-dimensional pose data. The method additionally includes applying the three-dimensional pose data, the estimate for the ground reaction force, and the estimate of the hand force, to a neural network or other model to optimize the estimate of the hand force and the estimate of the ground reaction force.