Experimental, fitted, and predicted forces in response to the VFT20-VFT80 train combination from a typical subject at different shortening velocities during the model development phase. For each row, the shaded panel represents the fittings of the VFT20-VFT80 experimental data to that velocity, while the non-shaded panels represent model predictions to the other three velocities. For example, the shaded panel (f) at -75°/s represents the fitting of the isovelocity model to the experimental forces data, while the non-shaded panels (e), (g), and (h) are the predictions of the model at -25°/s, -125°/s, and -200°/s, respectively. These data were used to determine the best velocity to identify the parameters V1 and V2. RMS Force (N) errors between measured and modeled force data in response to the VFT20-VFT80 train are presented in each panel. It should be noted that the experimental data in the figure are means of two trails.