## 1 Introduction
The International Standards Organization (ISO) describes the effectiveness and efficiency of, and satisfaction with, a product as usability parameters [9]. [PERSON] defined usability attributes as effectiveness, learnability, flexibility, and user attitude [10]. According to [PERSON] and [PERSON], the usability parameters are initial performance, long-term performance, learnability, retainability, advanced feature usage, first impressions, and long-term user satisfaction [11]. [PERSON] defined the usability parameters as ease of use and learning [12]. The parameters defined by ISO and Nielsen are commonly used for usability evaluation [13]. There are several usability evaluation techniques. Any approach or technique used to perform usability evaluation or testing to enhance the usability of an interactive system at any point of its development is known as a usability evaluation method (UEM). Several usability testing methods have been introduced, such as laboratory-based formative assessment with users, heuristics, questionnaires, and other expert-based usability evaluation techniques, model-based analytic approaches, all types of expert assessment, and the remote evaluation of interactive software after field deployment. The factors that influence the adoption of smart wearable devices among potential customers are wearability, ease of use, compelling design, functionality, and price. Wearability refers to the existence of pain, degree of comfort, ease in wearing, requiring support to wear, or willingness to wear again. Meanwhile, ease of use means no interference in daily activities, comprehensibility, and learnability. Compelling design means visually appealing. Functionality refers to the core features. Although conventional usability evaluation methods such as thematic analysis, heuristic evaluation, interviews, and think-aloud and cognitive walkthroughs can be used, the main shortcoming of these methods is that the findings in a laboratory can sometimes be difficult to illustrate [14]. Alternatively, the Agency for Healthcare Research and Quality has suggested that questionnaires can be effectively used for usability evaluation [15]. The most widely used questionnaires are the system usability scale (SUS) and UTUAT, the post-study system usability questionnaire covering use, satisfaction, ease, etc. The dependability and accuracy evaluation of wearable devices are currently the focus of extensive research. Concerns have been raised relating to the use of wearable devices, and researchers have indicated the importance of combining behavioral change approachessuch as goal setting, feedback, and rewards alongside other evidence-based techniques [15]. A mixed response to adopting wearable devices has also been observed, with the response of users being less positive than expected [5]. In addition, whilst wearable technology represents a significant range of potential applications, usability issues still remain to be solved by research [5]. Two key features have also been identified that are critical for a product's success: the acceptability of the items to regular consumers and their comfort level [6]. Therefore, the usability issues of wearable devices remain to be solved, as their success depends on users' experience; therefore, it is critical that a wearable device is easy and intuitive to use and comfortable to wear. As a result, continuous usability testing is essential for manufacturers to ensure the widespread and rapid adoption of their particular product. This testing observes users interacting with the product or prototype and is a key factor in ensuring a satisfactory user experience. The key aim of this paper is to investigate the usability and other issues relating to the existing commercially available wearable smartwatches. The usability will be analyzed based on the customized heuristic evaluations and the system usability scale (SUS).