This paper investigates the increasing popularity of fitness in China, particularly in the context of the internet and consumer societies. While fitness was introduced earlier, its recent surge is a novel phenomenon not fully explained by existing research on sports, fitness, or the body. The study focuses on the impact of the mobile internet, exemplified by the fitness app Keep, on the discipline mechanisms surrounding fitness. The research questions are: 1) Does the discipline mechanism still exist in the absence of traditional supervised teaching, and how has it changed? 2) Can the widespread passion for fitness be explained by internal self-discipline, and if so, what type? 3) Has the mobile internet impacted the distribution of power in this context? The authors acknowledge the historical context of fitness in China, noting its initial association with national rejuvenation in the early 20th century, followed by suppression and later resurgence fueled by a shift towards market economics and the influence of foreign fitness culture. The rise of fitness apps like Keep signifies a further shift, moving fitness training from gyms to everyday life spaces and highlighting the need for a new understanding of discipline in this changing environment.

The study reviews sociological perspectives on the body, starting with Foucault's theory of discipline and its application to sports. Foucault highlighted the use of space distribution, coding activities, and hierarchical monitoring to produce a 'tame body.' The authors contrast this with Elias's work on civilization and Baudrillard's on consumer society. Elias emphasizes the increasing control over the body in modernity and the role of rational consciousness, while Baudrillard's perspective sheds light on how fitness practices can be seen as a form of consumption contributing to identity formation and social distinction. Existing research on fitness often focuses on gender discipline or uses the self-presentation perspective to explain individual motivations. The authors argue for a more comprehensive analysis incorporating external discipline strategies and internal self-discipline to fully account for the fitness phenomenon's popularity.

The paper employs a qualitative approach focusing on the analysis of popular fitness sports and the Keep fitness app as a case study. While acknowledging the limitation of generalizing findings based on a single app, the authors justify this choice because Keep is a widely used app representing a significant portion of the Chinese market. Its features allow for detailed analysis of how technology shapes discipline and self-discipline in fitness practices. The authors examine the app's structure and features to identify how external discipline mechanisms function in the digital realm. They analyze the different strategies employed, including the "spatial strategy" (liquidity and visibility), "time strategy" (linear time and rhythmization, use of fragmented time), and the "knowledge strategy" (the provision and dissemination of fitness knowledge). To understand the internal motivative mechanism of self-discipline, they use the framework of consumption theory, particularly from the perspective of Baudrillard. They explore how the manipulation of codes, time consumption, and moral display combine to create distinction and contribute to the individuals' dedication to fitness practices. Lastly, they analyze "self-writing", which represents users' active participation in constructing and shaping fitness knowledge and identity through the app's features.

The study identifies how the Keep app, and by extension, the internet, has upgraded external disciplinary strategies. **Spatial Strategy:** The app creates a liquid and visible space for discipline, extending it beyond traditional gym settings into everyday life. The technology of "locating individuals" enables monitoring and connection among users, creating an "omnipticon" where many watch many and a "synopticon" where many watch a few (experts). **Time Strategy:** The app implements a linear and rhythmic time strategy, structuring fitness routines into sequential courses with specified durations. This transforms free time into "socially necessary labor time," mimicking the production process of an industrial good. **Knowledge Strategy:** Keep's extensive database of fitness knowledge, including courses, dietary guides, and other information, creates a comprehensive discourse system that guides and regulates users' practices. Users have freedom of choice within the framework established by the app. The authors go beyond external discipline to explain the driving force behind the users' commitment to fitness. They analyze the concept of self-discipline, which in the context of the study means active acceptance and engagement with the fitness norms and discourses. They find four key components of self-discipline in Keep's users: **Code Manipulation:** Users actively engage in selecting and using codes to define and refine their identity and establish social standing. The process is a form of consumption, constantly creating distinctions among practitioners. **Time Consumption:** The significant time investment required in fitness, particularly its "time currency" aspect, distinguishes it from other consumer practices and reinforces its value in building identity. **Moral Display:** The app uses slogans and aphorisms to promote values of self-discipline, independence, simplicity, and nature. These ethical codes are essential in distinguishing fitness practitioners from non-practitioners. **Self-Writing:** Users' active participation in generating and sharing fitness knowledge and experiences creates a sense of community and ownership, reinforcing the overall discourse and shaping the practice's identity. The study concludes that fitness practices in the digital age represent a form of consumption that fosters a new type of self-discipline, leading to both individual self-improvement and the creation of social distinctions.

The findings address the research questions by demonstrating that discipline mechanisms still exist in the digital age, but in transformed ways. The mobile internet has not eliminated discipline; rather, it has extended and intensified it, creating new forms of control and self-regulation. The study reveals that the widespread passion for fitness is driven not only by external pressures but also by internal self-discipline, motivated by factors beyond mere health and aesthetics. This self-discipline is a crucial component in identity construction and social distinction among fitness practitioners. The results highlight the interplay between technology, power, and individual agency in shaping contemporary practices. The mobile internet is not simply a neutral tool; it actively participates in shaping and reinforcing social norms and power dynamics. This study contributes to a more nuanced understanding of the dynamics of discipline and self-discipline in the context of digital culture and consumer society.

This study offers a novel perspective on the growing popularity of fitness in China by examining the interplay between external discipline strategies and internal self-discipline in the context of internet technology. It highlights the role of fitness practices as a form of consumption contributing to identity formation and social distinction. The findings suggest that the mobile internet, instead of breaking down disciplinary mechanisms, has transformed them, extending their reach and intensifying their effects. Future research could explore similar patterns in other domains of life, examine the specific cultural variations in the experience of self-discipline, or investigate the long-term social and psychological effects of this novel form of self-regulation.

The study is based on the analysis of a single fitness app, Keep, which may limit the generalizability of findings to the broader fitness landscape. While Keep represents a significant portion of the market, other apps or platforms may exhibit different features and dynamics. Future research should investigate whether the observed trends and patterns are replicable across different platforms and regions. Additionally, the study relies heavily on qualitative data analysis, limiting the extent to which quantitative measures can be used to support the arguments.