## 2 Materials and Methods
### Procedures
#### 2.3.1 Data Processing  
The beginning of shoulder elevation movements was defined as the first instant when acceleration recorded by the hand sensor exceeded the mean resting value by \(\pm\)0.3 m/s\({}^{2}\). Thereafter, new phases of the movement were defined every 3 s. For the drinking task, the phases were defined based on the criteria outlined in Table 3.  
The EMG signals were digitally filtered using a second-order band-pass Butterworth filter with a pass band from 20 Hz (or 50 Hz, in cases where heart noise was detected) to 450 Hz, to remove noise. The root mean square (RMS) was then computed using a sliding window of 100 samples. Hand acceleration signals were subjected to low-pass filtering using a fourth-order Butterworth filter and a cut-off frequency of 4 Hz [76]. To normalize the data, the mean RMS muscular activity level for each muscle during each phase was divided by the maximum [38] RMS value achieved during each muscle's SVIC and then multiplied by 100. Then, the mean EMG values for each phase of the movements/drinking task phases were calculated. To assess relative activation of scapular muscles, three muscular ratios [78] were computed, considering muscle involvement in scapulothoracic motions, specially upward and downward rotation (DrvsUr), abduction and adduction (AdvsAb), and elevation and depression (DepvsE)], according to the following formulas:  
\[\text{DrvsUr ratio}=\frac{\text{LS activity level}}{\text{LS}+\text{UT}+\text{MT}+ \text{LT}+\text{SAup}/\text{med}+\text{SAlow activity level}} \tag{1}\] \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Phase’s Name** & **Description** & **Start** & **End** \\ \hline \multirow{4}{*}{Reaching} & Beginning from the starting position & Hand sensor’s acceleration & \\  & with the upper limb at the side of & exceeded the mean resting value by & \\  & the body, until reaching the bottle & \(\pm\)0.3 m/s\({}^{2}\)[76] & \\ \cline{3-4} Forward transport & Bringing the bottle towards & Elbow angle is in maximal & \\  & the mouth & extension [77] & When shoulder elevation starts \\ Drink & Drinking a sp of water & After forward transport, when & \\  & & shoulder elevation starts & \\ Backward transport & Put the bottle back on the box on the & When shoulder reaches & \\  & table & maximum elevation & Elbow angle is in maximal extension [77] \\ Returning & Moving back to the upper limb & Elbow angle is in maximal & Hand sensor’s acceleration below \(\pm\)0.3 m/s\({}^{2}\) \\  & starting position & extension [77] & of the mean resting value [76] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Definition parameters from the phases of the drinking task. \[\text{AdvsAb ratio}=\frac{\text{MT}+\text{LT activity level}}{\text{MT}+\text{LT}+ \text{SAup}/\text{med}+\text{SAlow activity level}} \tag{2}\]  
\[\text{DepvsEl ratio}=\frac{\text{LT activity level}}{\text{LT}+\text{UT}+\text{ LS activity level}} \tag{3}\]  
Specifically, for each phase of the movement/drinking task, a value ranging from 0 to 1 was achieved [where 0 indicates no activity of the muscle(s) antagonist(s) for the respective motion and 1 indicates no activity of the muscle(s) agonist(s) for the motion under consideration]. The scapula's resting position and the range of scapula and shoulder movements of each of phase of the movement/task were calculated using either the mean or the difference between joint angles' values, namely, (a) the scapula's resting position, calculated by averaging the resting values recorded during the first 5 s of recording; and (b) the elevation and lowering phases and drinking phases, calculated by the maximum range variation from the starting position of each phase.