## 2 Materials and Methods
### Intervention  
All study procedures were conducted with approval by the authors' institutional review board and with informed consent from the participant. A standard protocol was used for all study procedures to ensure repeatability across this study as well as in future work. A set of five wireless, water-resistant sEMG sensors (Biostamp RC\({}^{\text{\text{\textregistered}}}\), MC10 Inc., Lexington, MA, USA) were placed on the participant's left upper extremity. Each sensor was 6.6 \(\times\) 3.4 \(\times\) 0.3 cm\({}^{3}\) in a housing made of a flexible, low-durometer silicone. These sensors were selected from many research lab-owned systems due to their low profile, flexibility, remote monitoring capabilities, and ability to sanitize in-hospital environments [28; 29]. Prior to placement, the skin was prepared by washing with soap and water, and electroconductive gel was applied to each sensor. Sensors were placed at the anterior deltoid, long head of the biceps, and lateral head of the triceps according to the Surface Electromyography for the Noninvasive Assessment of Muscles (SENIAM) guidelines standard placement procedures [30]. Sony anatomical landmarks of the medial and lateral humeral epicondyles were used for standard placement of the subsequent two sensors at the wrist flexor and extensor muscle groups, as SENIAM does not offer placement guidelines for these muscles (Figure 2). To further ensure consistency, the same researcher placed the sensors at each data collection visit. Due to the size of the sensors, only large muscles and groups could be observed. The sensor placement allowed for the observation of proximal and distal muscle activation. The setup and placement of the sensors took approximately 10 min. Individual serial numbers were used to consistently pair the same set of sensors and muscles. \begin{table}
\begin{tabular}{c c} \hline \hline
**Days Post Stroke** & **Qualitative Functional Assessment** \\ \hline
7 & Patient demonstrated progress but also having difficulty with engaging left upper extremity fingers \(\dots\) Patient presented with emerging 2 point pinch and full palm grasp and release today. \\ \hline
10 & Patient showing increased function in his left upper extremity. Fine/gross motor activity with great improvement and effort compared to previous session. \\ \hline
12 & Patient participated in fine and gross motor strengthening and coordination with great effort. Demonstrating great key pinch and emerging pincr pinch. \\ \hline
14 & Continues to demonstrate good progress with left upper extremity function performing exercises with great effort and improved control. Continues to need more work on wrist extension, thumb abduction, and middle/ring finger control. Difficulty with coordinating movements. \\ \hline
17 & Patient presented with improved left upper extremity function. Increased coordination compared to previous session. \\ \hline
19 & Patient demonstrated great progress again. Participated in fine motor activity with great effort and minimum cues for coordination. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Functional assessment documented in EMR. Muscle signal data were collected for three to four hour sessions every one to three days, beginning on post-stroke day three through discharge from inpatient rehabilitation. Session length was limited by the local memory storage allowance (32 MB) of each sensor. During each session, a researcher documented activity at 30-min intervals, but did not remain in the room throughout data collection, so as not to interfere with regularly scheduled activities or rest (Table 2). Two additional follow-up sessions in the community were conducted at three and eight months post-stroke, at the participant's place of work. The same protocol was used for sensor placement and data collection in the community for consistency, with the exception of [PERSON] tracking his activity (e.g., desk work or exercise) himself and reporting this to the researcher.