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The knee loads (tibiofemoral force) during late stance (where we are more confident with our model validity) are lower during the gastroc avoidance gait cycle than the more gastroc gait cycle. The magnitude and shape of the gastroc avoidance profile matches the simulation results from Demers et al. (2014). The early stance knee loads from the more gastroc case are less than one body weight, which along with the lack of early stance extension moment (plot above) indicate an under representation of the quadriceps muscles. This is confirmed in the plot of active fiber force along the tendon of the quadriceps muscles below.
Future Work
Further work is necessary to improve the agreement of the inverse dynamics joint moments and forward dynamics joint moments. Hand tuning parameters associated with converting EMG to control inputs (delays, scale factors) is a place to start, along with hand tuning optimal fiber force, optimal fiber length, and tendon slack length to make the joint moments match more closely. For example, shortening the optimal fiber length of the vasti could cause them to generate more passive force during early stance, solving one of our identified problems with the current results. For a more comprehensive tuning of parameters, we could use CEINMS to tune parameters using other motion trials before running the forward simulations of the motions we care about.
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