## 4 Discussion
### Limitations  
This study has a number of limitations. First, our attrition rate was relatively high at 28.6%. The most reported reason for withdrawal (9/12) was due to disliking the vibrotactile cues. To address this concern, we amended our protocol to allow participants to receive a demonstration of the system prior to enrollment; after implementing this change, we had no further dropouts due to this reason. Although we expect this change in protocol to improve attrition for future studies, it will be important to also consider alternative methods of cue delivery to be more inclusive of individuals who will not tolerate the vibrotactile sensation of our current cues. Alternative methods of cue delivery may also expand the accessibility of our system to individuals with greater sensory impairment, such as severe sensory loss or neglect. However, further research is needed, as only two participants in our study had sensory deficits per FMA-UE sensory scores, limiting our ability to draw statistical conclusions about this group. Of note, no participants withdrew from the study due to disliking the progressive-challenge activity program. Despite our attrition rate being higher than expected, we completed our study with a high recruitment rate of 5.25 consents/month. Furthermore, we were able to follow-up with a majority of participants (76.7%) for the at-home phase of the study. By contrast, a systematic review by [PERSON] et al. (2020) reported that median recruitment rates in stroke rehabilitation studies were much lower, with a median recruitment rate in North America of 1.35 consents/month [66]. Attrition rates are known to be highly variable in stroke rehabilitation studies and are dependent on the study location, length, and setting [66]. A systematic review by [PERSON] et al. (2020) consisting of 512 randomized control trials with 28,804 stroke survivor participants found attrition rates ranging between 0 and 83%, with a median of 6% [66]. While our study's attrition rate is higher than this reported median, it is comparable to that of another study investigating the feasibility of a wearable system among stroke survivors in an IRF (a reported attrition rate of 29%) [34]. The wearable system in that study was designed to provide feedback on upper limb activity and to prompt activity during inactive periods to assist the patient in reaching a clinician-set goal for upper limb movement. From a total of 17 recruited participants, the authors reported that 3 withdrew from the study due to the psychological burden of using the wearable system in combination with other therapies, 1 withdrew due to an allergic reaction to the device straps, and another withdrew due to early discharge. No participants reported withdrawing due to disliking the vibrotactile system, perhaps indicating that feedback and goal setting may reduce attentional focus on the vibrational stimuli themselves but add to patient perceptions of cognitive burden. We acknowledge, as another limitation of the study, several sources of bias toward a more favorable user experience. Participants who withdrew from the study prior to completing 3 days of the progressive-challenge activity program did not complete user experience surveys. A reasonable critic could argue that those who withdrew due to disliking the vibrotactile cues would have rated the system less favorably compared to those who tolerated the cue sensation. Bias toward more positive user experiences is also inherent to the study in that individuals who are more likely to consent to participating in an activity program using wearable technology may be more likely to perceive it favorably. Given that a high percentage of patients approached for the study consented to participate (72.4%), individuals in the immediate aftermath of stroke may be particularly motivated to use wearable systems promoting independent therapeutic activity. A general limitation of wearable technology used remotely is the likely possibility of missing data.