Although research on physical fitness science in Japan has developed along with occupational health issues, the role of researchers in this area has been reduced by technological advancements. Nowadays, the automation and mechanization of manual tasks have created new occupational problems. These new problems affecting workers, such as prolonged occupational sitting and a decline in cardiorespiratory fitness (CRF), have been shown to increase the risk of several diseases (i.e., diabetes, obesity, heart diseases, and mortality), and further studies are needed to clarify this issue. Furthermore, in response to changes in the social structure due to the “low birthrate, aging society, and shrinking population”, a workforce with a different form than that from the postwar period is required. Therefore, the need to consider how we can avert this national crisis with the new role of researchers in the field of physical fitness science is once again drawing attention. In this article, we introduce the research being conducted by the National Institute of Occupational Safety and Health in Japan to meet the needs of “healthy and long working” and discuss this research in the context of future issues. Specifically, we introduce the development of a tool (the Worker’s Living Activity-time Questionnaire) to assess workers’ sitting time and epidemiological research using it. Finally, we describe the efforts to develop a new index for evaluating workers’ CRF and social implementation experiments to make the workplace a base for health promotion.