Figure 1.

The model has three inputs: The desired speed, the desired elevation, and the set of muscle weightings characterizing the baseline condition (elevation 0% and speed 3 km/h). The outputs are predicted motor components (weightings and excitation primitives) as well as the synthetic muscle excitation profiles (MEP) for the muscles under study. The generic Excitation Primitive block (D) was determined using the non-negative factors collected experimentally (A). The Regression Model block (C) was determined using experimental muscle weightings (B). The Weightings Predictor block (E) produces the estimated muscle weightings for a given speed and elevation. The MEP Reconstruction block (F) realizes the linear combination of the excitation primitives and the estimated muscle weightings. The model can be applied in two modes, the Subject-Generic Mode (SGM) and the Subject-Specific Mode (SSM), depending whether the input baseline weightings are generic (subject group average) or experimentally obtained for a specific subject.