## 1 Introduction  
Apps related to digital health and physical activity are very common in app stores, including fitness apps. These applications are third-party software for smartphones or wearable devices that assist users in recording fitness data, guiding motor learning, and navigating a healthy lifestyle [1]. They offer integrated services combining educational, tracking, social, gamification, and motivational features that support healthier lifestyles and exercise habits [2]. Fitness apps have emerged to facilitate the more efficient integration of user needs and fitness resources, enhancing user engagement. Moreover, the end users of these applications are not only the customers of fitness app services but also a source of valuable data. Hence, the industry must identify strategies to attract more seniors to engage with fitness apps and actively participate in digital healthcare. The growing popularity of fitness apps and the rapid growth of the internet economy have attracted the attention of scholars in the fields of sociology, design, and psychology. Despite a significant amount of research in this area, there is little research on older Asian users [2]. Technology supporting personal health management may benefit seniors [3], as 80% suffer from at least one chronic condition [4]. It is postulated that Asian seniors may benefit from exercise in terms of both physical conditioning and quality of life [5]. The available evidence suggests that digital health technology can significantly enhance quality of life and promote physical and mental well-being [6]. Fitness apps provide seniors with a valuable service combining education, tracking, social interaction, gamification, and motivation, significantly enhancing physical and mental well-being. However, the intention to utilize and adopt such apps among Asian seniors remains relatively low [7]. As individuals age, they may experience cognitive decline, including impairments in memory and learning, making the acceptance of new technologies challenging [8]. [PERSON] et al. [9] specifically argue that there are differences in motivation, planning, and habits of using new information technology between seniors above 50 years of age and those below the age of 50. This indicates that the age factor can be used for market segmentation. It is necessary to conduct further research to determine the specific needs of this group of users. Therefore, the population targeted is classified as Asian seniors above 50 years of age. Furthermore, most current studies on user motivation regarding fitness apps have taken expectation confirmation theory (ECT), the technology acceptance model (TAM), and the unified theory of acceptance and use of technology (UTAUT) as the theoretical basis to inspect the issue of general users' continuous use of fitness apps, focusing on the problem of decision intention to engage more users in fitness apps [10; 11; 12]. Nevertheless, only a limited number of studies have been conducted on the factors that influence user experience, with insights drawn from the diffusion of innovation theory. There remains a need for further research on Asian seniors, since their technology acceptance may differ from that of younger users. It is also possible that a gap exists in understanding how fitness apps influence exercise adherence in this demographic. Most existing research focuses on technological characteristics rather than experiential factors shaping older Asian users' engagement [13]. This study integrated the technology acceptance model and diffusion of innovations to propose a theoretical model aimed at addressing seniors' acceptance behavior of fitness apps based on user experience factors. The principal advantage of integrating these theories was the use of the structure of the diffusion of innovations as a key input for forming the technology acceptance model.