## 4 Discussion  
In this pilot study, we measured the glenohumeral motion and scapulothoracic angles during the shoulder flexion and abduction of paretic and non-paretic arms in a sample of post-stroke patients. The scapulohumeral rhythm was also calculated to shed light on the nature of shoulder dysfunction. Preliminary data were gathered from seven post-stroke patients to assess the feasibility of the wearable approach proposed by [PERSON] et al. (2018). \begin{table}
\begin{tabular}{l c c} \hline \hline  & **SHR Paretic Side** & **SHR Non-Paretic Side** \\ \hline
30\({}^{\circ}\) abduction & 3.3 & 4.9 \\
60\({}^{\circ}\) abduction & 3.6 & 4.7 \\
90\({}^{\circ}\) abduction & 3.8 & 5.3 \\
120\({}^{\circ}\) abduction & 3.7 & 5.8 \\ Max. abduction * & 4.7 & 5.4 \\ \hline
30\({}^{\circ}\) flexion & 6.0 & 7.2 \\
60\({}^{\circ}\) flexion & 4.1 & 4.7 \\
90\({}^{\circ}\) flexion & 3.8 & 4.2 \\
120\({}^{\circ}\) flexion & 3.7 & 4.6 \\ Max. flexion * & 3.6 & 4.8 \\ \hline \hline \end{tabular} \({}^{\circ}\) 139.7\({}^{\circ}\) for the paretic side and 171.3\({}^{\circ}\) for the non-paretic side; \({}^{\lx@sectionsign}\) 121.4\({}^{\circ}\) for the paretic side and 141.8\({}^{\circ}\) for the non-paretic side.  
\end{table} 
Table 4: SHR during arm abduction and flexion. Figure 2: Top panels: scapulothoracic UD on the paretic side (**a**) vs. the non-paretic side (**b**) for different degrees of humeral abduction. Bottom panels: scapulothoracic UD on the paretic side (**c**) vs. the non-paretic side (**d**) for different degrees of humeral flexion. This approach is very clinically oriented since it is valid and reliable when compared with a gold-standard optoelectronic system, and it is user-friendly and not time-consuming. Reference data exist [29], as well as other clinical applications in patients with rotator cuff tears [30]. The results show that patients with stroke presented a reduced scapular posterior tilt of the paretic shoulder during maximum flexion and during abduction at 60\({}^{\circ}\) and 90\({}^{\circ}\) compared with the non-paretic side. An abnormal scapular tilt was also correlated with the Fugl-Meyer score. Unfortunately, the lack of reference data on the kinematics of the shoulder using wearable devices made it impossible to compare the findings of the present pilot study. The only data available are from the study by [PERSON] et al. [22] for the active range of motion of the shoulder in a group of 20 stroke patients before rehabilitation, measured using IMUs, but the details of the IMUs were not included in the study. The measured flexion of the paretic shoulder was 85-81\({}^{\circ}\) in the study and control group (with a large standard deviation of 42.6-36.9), respectively, and it was, on average, less than the humeral RoM we measured in our study. However, comparisons can be made with studies carried out using non-wearable devices for 3D instrumental shoulder kinematics assessment, which is considered the gold standard [8; 31]. Unfortunately, one problem encountered is that most of these studies differ in the explored shoulder motion (i.e., elevation in the sagittal plane, the frontal plane, the scapular plane, or a self-selected plane, or motion during activities of daily life) and in the examined arm compared with its control (i.e., paretic vs. non-paretic upper limb or dominant vs. non-dominant limb). Furthermore, some authors only published graphs and no relative data [11; 13; 15], therefore making it difficult to compare the studies [5]. The maximum flexion and abduction findings in the current study (121.4\({}^{\circ}\) and 139.7\({}^{\circ}\) for peak flexion and peak abduction, respectively) are not comparable to other studies where, usually, scapular motion was measured at fixed humerothoracic angles (30\({}^{\circ}\), 45\({}^{\circ}\), 60\({}^{\circ}\), and 120\({}^{\circ}\)) and a maximum range of motion was not reported. Only [PERSON] et al. [5] reported 130.5\({}^{\circ}\) of maximum humeral abduction in 16 post-stroke patients, while [PERSON] et al.