## 3 Results
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Variable** & \
\begin{tabular}{c} **Mean Across Cycles.** \\ **Mean (STD)** \\ \end{tabular} &
\begin{tabular}{c} **99 Percentile (All Cycles).** \\ **Mean (STD)** \\ \end{tabular} \\ \hline Knee moment (N.m) & \(-\)29.5 (12.6) & 11.1 (4.6) \\ VL force (N) & 275.1 (117.9) & 679.7 (222.8) \\ VM force (N) & 117.8 (50.4) & 290.6 (94.3) \\ Tibia normal force (N) & 1018.0 (203.0) & 1974.0 (364.0) \\ Tibia tangent force (N) & 89.6 (30.7) & 348.1 (71.6) \\ \hline \hline \end{tabular}  
* The left column shows the mean and standard deviation of the mean values in each trial. The right column shows the mean and standard deviation of the maximum values, calculated as the 99 th percentile for each trial. Knee moments are the moments associated with the gravitational, inertial, and external actions of the FDM. Positive knee moments are extensor, and negative moments are flexor.  
\end{table} 
Table 2: Summary of dynamic variables estimated using the full dynamic model FDM *. \(n=15\). Figure 4: Contribution of each component of the dynamic model to the generalized forces in the knee. Full dynamic model: it includes the forces of the platform, the weights of the foot and leg, and the inertial forces of the foot and leg. External: it represents the contribution associated with the force of the platform on foot. Gravitatory: it measures the effect on the joint moment of the weights of the leg and foot. Inertial: contribution of inertia forces, associated with the leg and foot on the joint moment. As can be observed, the correlation between the estimated muscle force and the measured EMG signals is excellent, with mean values higher than 0.93 for both muscles and both directions of motion. This reveals that model-based estimated muscle forces are coherent with the measured EMG values: they both increase and decrease in the same manner. On the other hand, Table 5 presents the agreement between the estimated muscle forces using the SGM and the estimation of the same forces obtained by the Force-EMG calibration curves. These calibration curves were obtained for each subject based on data (estimated muscle forces--measured EMG signals) from two load conditions: L0 and L2. These curves were used to estimate the forces from the EMG signals and in the exercise with L1 load condition. These results provide an excellent correspondence between the model-based estimated forces and those obtained based on Force-EMG calibration. The mean ICC values were higher than 0.96 for both muscles and both directions of motion of the knee. The 25 th percentile is greater than 0.9 in all cases. With respect to the error level, the mean error was in the order of 5.5% of the force range, while in 75% of cases it was lower than 8%. Figure 5 displays an example (subject # 3) with excellent correspondence between the results of the model and those obtained from the EMG signals. Both signals are perfectly synchronized, and the differences are very small and are limited to motion extremes. Table 6 shows the results of agreement between the reaction forces in the directions normal and tangential to the tibial plateau as estimated by the quasistatic model, and as measured directly using an instrumented prosthesis [26]. As can be observed, the ICC value is very high for the normal force (0.945), with an error in the order of 6% of the total range. With respect to the force in the tangential direction, the ICC had a worse but still acceptable value (0.827). In this case, the error was in the order of 10% of the total range of this force, which is also small. Figure 6 presents the measured and estimated forces. As can be observed, the directly measured force has high noise, especially at the beginning of the motion. This noise was smoothed before calculating the agreement parameters (Figure 6 shows the raw signal). As can be seen, despite this noise, the correspondence between the reaction forces (in the normal and tangential directions) is good: measured and estimated forces are in-phase, and had similar amplitudes.