# EMG-Assisted Algorithm to Account for Shoulder Muscles Co-Contraction in Overhead Manual Handling
## 3 Results
### Joint Reaction Forces  
The magnitude of the estimated GH force was higher with EMGA compared to SO and SOcal. However, EMGA solutions did not present any sudden peaks in the force amplitude for the duration of the test, unlike SO. These SO peaks were smoothed out when using SOcal (Figure 7a). Peaks also \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Muscles**} & \multicolumn{3}{c}{**RMSd**} & \multicolumn{3}{c}{**R**} \\ \cline{2-7}  & **SO** & **SOcal** & **EMGA** & **SO** & **SOcal** & **EMGA** \\ \hline Anterior Deltoid & \(0.34\pm 0.11\) & \(0.27\pm 0.10\) & \(0.11\pm 0.07\) & \(0.46\pm 0.31\) & \(0.53\pm 0.29\) & \(0.90\pm 0.09\) \\ Median Deltoid & \(0.25\pm 0.13\) & \(0.21\pm 0.07\) & \(0.08\pm 0.04\) & \(0.37\pm 0.42\) & \(0.22\pm 0.39\) & \(0.88\pm 0.16\) \\ Posterior Deltoid & \(0.13\pm 0.07\) & \(0.13\pm 0.09\) & \(0.08\pm 0.05\) & \(-0.17\pm 0.26\) & \(-0.08\pm 0.30\) & \(0.31\pm 0.51\) \\ Pectoralis Major & \(0.09\pm 0.09\) & \(0.10\pm 0.09\) & \(0.11\pm 0.08\) & \(0.17\pm 0.37\) & \(0.11\pm 0.36\) & \(0.34\pm 0.41\) \\ Latissimus Dorsi & \(0.16\pm 0.16\) & \(0.11\pm 0.09\) & \(0.12\pm 0.08\) & \(-0.13\pm 0.37\) & \(-0.19\pm 0.35\) & \(0.49\pm 0.44\) \\ Infraspinatus & \(0.32\pm 0.15\) & \(0.25\pm 0.13\) & \(0.06\pm 0.04\) & \(0.32\pm 0.30\) & \(0.28\pm 0.29\) & \(0.85\pm 0.17\) \\ Supraspinatus & \(0.31\pm 0.15\) & \(0.28\pm 0.17\) & \(0.06\pm 0.05\) & \(-0.05\pm 0.31\) & \(-0.13\pm 0.33\) & \(0.76\pm 0.30\) \\ Subscapularis & \(0.24\pm 0.20\) & \(0.21\pm 0.20\) & \(0.06\pm 0.04\) & \(0.06\pm 0.34\) & \(0.01\pm 0.37\) & \(0.56\pm 0.29\) \\ Biceps & \(0.18\pm 0.08\) & \(0.14\pm 0.06\) & \(0.05\pm 0.03\) & \(-0.36\pm 0.30\) & \(-0.28\pm 0.33\) & \(0.76\pm 0.24\) \\ Triceps & \(0.11\pm 0.07\) & \(0.11\pm 0.07\) & \(0.07\pm 0.06\) & \(-0.13\pm 0.26\) & \(-0.04\pm 0.33\) & \(0.30\pm 0.57\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: RMSd and R related to the muscle activations predicted by SO on the uncalibrated (SO) and calibrated model (SOcal) and the EMG adjusted with the EMG-assisted method (EMGA), in comparison to the experimental EMG. Figure 2: Net Adjusted EMG (EMGA: blue) and experimental EMG (Exp: red). * No experimental data (solid line: mean value, shaded region: 95% confidence interval). appeared for the joint reaction ratio throughout the test with SO (Figure 7b). A maximum ratio was reached close to the maximum extension of the GH joint with a mean value of 0.65 and 0.27 for the EMGA and SOcal, respectively. In comparison, the joint reaction ratio had an erratic behavior when estimated from SO. The direction of the GH force was directed within the stability cone for 100% of the trials for the SOcal and EMGA models, but not for the SO model (Figure 7b). Figure 4: Empirical cumulative distribution of all muscle activations (solid line: mean value, shaded region: 95% confidence interval) predicted by EMGA (blue), SO (orange) and SOcal (green): for a given activation (_a_), the ECDF shows the percentage of data who is at most equal to \(a\). Figure 5: Activation relationships between the rotator cuff muscles as predicted for the 6 and 12 kg trials: The axes show the activation value of the respective muscles. On the diagonal: the mean distribution of a given muscle activation over the trial. In the upper (lower) triangle: the relationship between two muscles activations throughout the trial. For instance, the EMG algorithm predicted that an increase in the activation of the infraspinatus is correlated with an increase of the supraspinatus’s activation. (Mean as predicted by EMGA: right, and SO: left). Figure 3: Muscle activations (solid line: mean value, shaded region: 95% confidence interval) predicted by EMGA (blue), SO (orange) and SOcal (green) * Teres major activation was synthesized. Figure 6: Coactivation coefficients between various muscle pairs (solid line: mean value, shaded region: 95% confidence interval) as predicted by EMGA (blue), SO (orange) and SOcal (green): the higher the coefficient, the higher is the muscle pair’s coactivation.